B. infantis abundance in the infant gut may be associated with growth and health outcomes. However, these relationships have not been widely studied in settings where B. infantis is a dominant early-life commensal and growth faltering is prevalent. Here, we estimated associations between neonatal B. infantis abundance and anthropometric outcomes up to 6 months of age in generally healthy infants in Dhaka, Bangladesh; diarrhoea and hospitalizations (at 1-2 and 6 months) were secondary morbidity outcomes. B. infantis stool absolute abundance was quantified by qPCR; for each infant, the primary exposure was mean abundance (0-28 days). Length-for-age, weight-for-age, and weight-for-length z-scores were derived at birth, 2, 3, and 6 months. Neonatal B. infantis abundance had a bimodal distribution, with 63% of infants having detectable B. infantis by 28 days of age. Anthropometric z-score distributions were shifted down, with means below zero. Neonatal B. infantis abundance was not associated with any anthropometric outcome at 2, 3, or 6 months of age (n = 830), or with the risks of diarrhoea or hospitalizations. The lack of association of neonatal B. infantis abundance with growth outcomes suggests that promoting early B. infantis colonization is unlikely to improve growth in populations with postnatal faltering.

Early life is a critical period for immune and metabolic development, but these patterns remain underexplored in populations from low- and middle-income countries. Here, we profile the microbiome and metabolome of 55 Bangladeshi mother-infant dyads over the first 6 months of life. Importantly, we observe an increase in microbially derived bile amidates and N-acyl lipids with age in conjunction with reads matching the bile salt hydrolase/transferase (bsh) gene. Although microbial source tracking confirms maternal fecal seeding, a substantial environmental contribution is also highlighted. Differences in infant fecal metabolic profiles are associated with delivery mode, maternal milk composition, household assets, and household-level water treatment. Cesarean section (C-section) delivery and untreated drinking water are linked to transient metabolic differences, including increases in bile amidates, N-acyl lipids, and other host-microbe co-metabolic products, including acylcarnitines. Multi-omics analysis reveals specific microbial-metabolite relationships, highlighting how early environmental and maternal living circumstances influence gut metabolic development through the microbiome.

BACKGROUND:The 25-hydroxyvitamin D (25(OH)D) concentration at which parathyroid hormone (PTH) concentration plateaus has been considered to benchmark vitamin D deficiency. However, in young children, there is limited evidence for a suppression point in the 25(OH)D-PTH relationship or its relevance to bone mass accrual. OBJECTIVES:To determine whether the threshold of 25(OH)D at PTH suppression in young children is corroborated by associations of 25(OH)D (or PTH) with bone mineral content (BMC) and areal bone mineral density (aBMD). METHODS:In a cross-sectional secondary analysis of data from the BONe and mUScle health in Kids (BONUSKids) study of 4-y-old children in Bangladesh, serum 25(OH)D and intact PTH (iPTH) were analyzed by liquid chromatography-tandem mass spectrometry and a chemiluminescent immunoassay, respectively. BMC and aBMD were measured by dual-energy X-ray absorptiometry. Associations between 25(OH)D, iPTH, and bone outcomes (BMC, BMC z-score, aBMD, and aBMD z-score) were modeled using multivariable-adjusted linear regression and spline models. Model fit was compared using Akaike's Information Criteria. RESULTS:Of 534 participants (51% female), 28% had 25(OH)D concentrations <25 nmol/L and 34% had iPTH >6.7 pmol/L. Model fit of the inverse relationship between 25(OH)D and iPTH was optimized with an inflection point at 25 nmol/L [<25 nmol/L: -0.16 pmol/L per 1 nmol/L increase in 25(OH)D; 95% confidence interval (CI): -0.22, -0.10; P < 0.001), above which the slope attenuated (≥25 nmol/L: -0.02 pmol/L; 95% CI: -0.04, -0.003; P = 0.019]. However, the positive linear associations between 25(OH)D and bone mass outcomes were monotonic (P < 0.05), and iPTH was not associated with any bone outcome in adjusted models (P > 0.05 for all). Associations were similar in males and females. CONCLUSIONS:Among 4-y-old children in Dhaka, Bangladesh, we did not identify a 25(OH)D threshold to define vitamin D deficiency based on its association with bone mass. However, efforts to raise 25(OH)D to ≥25 nmol/L may be warranted based on the relatively strong inverse association of 25(OH)D with iPTH below this threshold. This trial was registered at clinicaltrials.gov as #NCT03537443.

Angiogenesis is essential for placental growth and development. Improper placental vascular development can reduce blood flow to the fetus and increase the risk of adverse pregnancy and birth outcomes. The objectives of this study were to examine the effect of prenatal vitamin D supplementation on placental angiogenic factors and terminal villi, and associations between angiogenic factors, terminal villi and birth outcomes. This is a secondary analysis using data and specimens from the Maternal Vitamin D for Infant Growth trial in Dhaka, Bangladesh (n = 1298). Participants were enrolled at 17–24 weeks gestation and randomized to receive (IU/week): placebo, 4200, 16,800 or 28,000 vitamin D3 supplement until birth. Newborns and placentas were measured at birth. We examined a subset of randomly selected placentas (n = 80). Tissue sections were evaluated for vascular endothelial growth factor (VEGF-A) and placental growth factor (PlGF) using immunofluorescence. We measured intensity and percent area of expression for angiogenic factors, and total number and surface area of terminal villi. Vitamin D treatment effect was estimated using ANOVA. Regression models were used to assess associations of markers of placental angiogenesis with birth outcomes. Interactions by infant sex were examined. The overall mean (SD) percent area of expression was 17.0 (4.0) for VEGF-A and 15.0 (1.9) for PlGF. The mean (SD) number of terminal villi was 39 (15) per 12 in2, and surface area was 0.096 (0.040) in2. Vitamin D treatment groups were similar to placebo for all outcomes. No associations were observed between angiogenic factors or terminal villi placental and birth outcomes. Vitamin D supplementation starting from mid-pregnancy until birth did not affect expression of two key angiogenic factors or terminal villi in the placenta. Placental angiogenic factors or terminal villi did not have an association with birth outcomes. These results do not support a role of maternal vitamin D starting mid-pregnancy in impacting placental development.

Introduction: Heterogeneity in definitions of severe infection, sepsis and serious bacterial infection (SBI) in young infants limits the comparability of randomized controlled trials (RCTs) of infection prevention interventions. To inform the design of severe infection prevention RCTs for young infants in low-resource settings, we estimated the incidence of severe infection in an observational cohort of Bangladeshi infants aged 0-60 days and examined the effect of variations in case definitions on incidence estimates. Methods: In 2020-2022, 1939 infants born generally healthy were enrolled at two hospitals in Dhaka, Bangladesh. Severe infection cases were identified through up to 12 scheduled community health worker home visits from 0-60 days of age or through caregiver self-referral. The primary severe infection case definition combined physician documentation of standardized clinical signs and/or diagnosis of sepsis/SBI, plus either a positive blood culture or parenteral antibiotic treatment for >=5 days. Incidence rates were estimated for the primary severe infection definition, the World Health Organization (WHO) definition of possible SBI, blood culture-confirmed infection, and five alternative severe infection definitions. Results: Severe infection incidence per 1000 infant-days was 1.2 (95% CI 0.97-1.4) using the primary definition, 0.84 (0.69-1.0) using the WHO definition of possible SBI, and 0.026 (0.0085-0.081) using blood culture-confirmed infection. One-third of cases met criteria for the primary severe infection definition through physician diagnosis of sepsis/SBI rather than the standardized clinical signs, and 85% of cases were identified following caregiver self-referral despite frequent scheduled study visits. Conclusion: Severe infection incidence in young infants varied considerably by case definition. A severe infection definition that requires physician documentation of standardized clinical signs may miss a substantial proportion of cases identified by physician diagnosis of sepsis/SBI. In settings where health facilities are accessible, frequently scheduled home assessments by study personnel to identify severe infection in infants may not be necessary. ### Competing Interest Statement AF received consulting fees from Brigham and Women's Hospital for separate work on the diagnostic accuracy of clinical sign algorithms to identify sepsis in young infants. None of the other authors had competing interests to declare. ### Clinical Protocols ### Funding Statement The study was funded by the Bill and Melinda Gates Foundation (BMGF) under grant INV-007389 to The Hospital for Sick Children and grant GR-02268 to The International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b). BMGF had an advisory role in the overall study concept and design; however, the BMGF had no role in data collection, analysis, interpretation of data, writing of the article, and the decision to submit the article for publication. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Hospital for Sick Children Research Ethics Board (REB #1000063899) gave ethical approval for this work. The ethical review committee at the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) (PR-19045) gave ethical approval for this work. The ethical review committee at the Bangladesh Shishu Hospital and Institute (formally known as Dhaka Shishu Hospital), the ethical governing body for the Child Health Research Foundation (CHRF) (BICH-ERC-20/02/2019) gave ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes De-identified datasets and code files used in the analyses of this study are publicly available at the Borealis online data repository.

In early life, a child's physical growth and stature (e.g., weight, height, and head circumference) are shaped by genetic, nutritional, socioeconomic and other environmental factors. They are often examined as an outcome or exposure in population health research. In the framework of life course epidemiology or studies of the developmental origins of health and disease, various child growth patterns—such as 'impaired', 'excessive' or 'catch-up' growth—and the identification of 'critical' or 'sensitive' periods of growth related to health outcomes in later life have also been of particular interest [1]. In the current issue of Paediatric and Perinatal Epidemiology, Giacomini and colleagues [2] examine sex-specific associations between the growth of the head circumference in the first 5 years of life and potential behavioural problems at age 5 in a longitudinal birth cohort of 303 girls and 318 boys in Brazil. The study provides an opportunity to consider crucial but frequently overlooked methodological issues in studies of postnatal growth and its associations with later childhood outcomes. 'Growth' inherently means changes in a body size measured over a specified period. There are multiple ways to conceptualise and quantify growth in epidemiological research [3, 4], and importantly, the choice of growth metric and analytic approach to defining growth affects inferences and interpretations [5]. Gioacomini et al. [2] defined a child's head circumference growth in the first 5 years as the change in sex- and age-specific z-scores (HCZs) at birth and age 5 based on WHO standards, reflecting the absolute change in a child's relative size compared with an external reference measured at the two-time points, which may be referred to as a 'change score'. Gioacomini et al. [2] then categorised the change score into quintiles, with the lowest quintile of the change score as the reference group, which they referred to as 'impaired growth.' The change between two time points (t0 and t1) is an intuitive measure of growth in the absence of variability in actual measurement timing, but its use in regression modelling is not as straightforward as it might seem. First, the change score is mathematically coupled to the baseline head circumference (at t0). Due to regression to the mean, larger magnitudes of change in head circumference between birth and age 5 are expected for children whose head sizes at birth are closer to the tails of the HCZ distribution. This is reflected in their eTable 3 where the largest HCZ growth between birth and age 5 occurred among children whose HCZ at birth was categorised as small for gestational age, and the least 'growth' (in fact, the decline in the change score) among those whose HCZ at birth was large for gestational age. Gioacomini et al. [2] appropriately attempted to address regression to the mean by adjusting for head size at birth in the multivariable models so that the inferences about head growth are unaffected by baseline variation. Second, the coefficients for change scores as a measure of 'growth' do not provide clear interpretations, particularly when multiple age time points or intervals are simultaneously modelled. When there are only two measures of body sizes to quantify growth, the regression coefficient for the change score between time t1 and t0, adjusting for the size at time t0, is identical to those estimated using two commonly used alternative approaches: (i) regression of the outcome on size at time t1, adjusting for the size at time t0 (often referred to as a life-course model); and (ii) a two-stage approach whereby individual child-level model residuals are first generated by regressing size at time t1 on the size at time t0, then the residuals from the first stage are used as the exposure measure of interest in a second-stage regression model (referred to as conditional growth modelling). However, interpretations and meanings of results from these three approaches for each parameter are not identical. Interpretations of the coefficients for change scores across multiple time intervals are not intuitive, as each interval-specific change score estimate represents the cumulative 'effect' of growth up to the interval and later intervals [4]. Thus, change scores should be considered and interpreted cautiously, particularly with the increasing number of interval-specific growth measures. Another issue for consideration concerns generating z-scores as a body size or 'growth' measure and identifying 'impaired' growth. Expression of an anthropometric measurement as a z-score represents the relative standing of each child in comparison with a reference distribution. Therefore, changes in z-scores quantify growth differently from changes in absolute body sizes expressed using raw measures. The use of z-scores has an advantage in statistical modelling in that it accounts for different degrees of variances of body size (or change in size) distributions measured across ages due to differential rates of growth with age in childhood. However, the choice of reference or standards used to generate the z-scores can influence the interpretations of empirical analyses. The WHO growth standards used in Gioacomini et al. [2] are prescriptive—they define 'how children should grow under optimal conditions', including free of disease and healthy practices such as breastfeeding and nonsmoking [6]. These standards are widely used and recommended, yet numerous studies have demonstrated discrepancies in body size distributions, including head circumference, between the WHO standards and samples of comparable children in many countries [7, 8]. These results warrant a clear rationale for using WHO standards (or other references) to assess head growth within a study population. The choice of reference becomes more critical when investigators aim to categorise some children as having 'impaired' or 'excessive' growth, which implies that there are known clinical implications of memberships in such categories. Defining children in the bottom 20% of the distribution of change z-scores as 'impaired' growth is not only arbitrary but also unintuitive, given the defined 'impaired' growth reflects regression to the mean as discussed above. Contextual factors affect the distribution of anthropometric measures in a study population and, therefore, may also need to be considered when choosing a reference and identifying a particular change as 'impaired' growth. For instance, the Zika virus epidemic, first reported in May 2015 and spread across Brazil since then, has been linked to neonatal microencephaly [9]. The HCZ change score based on the WHO standards and the quintile-based category of 'impaired' growth among children born in 2015–2016 in Gioacomini et al. [2] may not reliably represent 'impaired' HC growth in other settings. Finally, Gioacomini et al. [2] also examined whether a 'sensitive' period of head circumference growth during the first 5 years of life may be more important for later problematic behaviours. They observed that the association between HCZ change from birth to age 5 is mainly driven by HCZ growth in the first 2 years. They separately assessed the associations of HCZ change from birth to age 2 and HCZ change from ages 2 to 5 with the behaviour scores. While this is an additional insight, a more comprehensive assessment could have been made by using all head circumference measures available in the study—at birth, 1, 2 and 5 years. Given the most rapid growth occurs shortly after birth followed by deceleration, growth in infancy (the first year) may be a more critical time window than the second year for behavioural problems in later childhood. The added complexity for the 1-year measurement can be managed using alternative growth metrics and analytical methods. For instance, the conditional growth modelling approach mentioned above could use a child's head circumference at each age after birth, adjusted for all prior measurements, as a growth metric to estimate interval-specific associations simultaneously, avoiding collinearity. This represents deviations from the expected size based on the child's earlier growth. Monitoring child physical growth and examining its long-term sequelae is essential in clinical practice and our efforts to improve population health. However, growth metrics that seem intuitive for describing a change in an individual child (e.g., change score) may not be the optimal approach in epidemiological analyses. Different definitions of growth and analytical approaches to estimating the effects of growth can yield different results, and they are complementary. Therefore, a comprehensive and robust understanding of child growth and its effects on later outcomes is most likely achieved by multiple approaches to quantifying and analysing growth in any given study. Both authors contributed to the conception and the content of the commentary. S.Y. drafted the manuscript and D.E.R. provided critical revisions. Both authors approved the final version. The authors declare no conflicts of interest. Data sharing not applicable as no datasets were generated or analysed for this commentary.

The early infant gut microbiota is generally dominated by bifidobacteria, but there is substantial variation at the (sub)species level. Patterns of postnatal Bifidobacterium subspecies colonization in low- or middle-income countries have not been widely studied. We used (sub)species-specific qPCR to quantify B. infantis (n = 1132), B. longum (n = 364), and B. breve (n = 399) in stool samples from infants (0-6 months of age) in urban Dhaka, Bangladesh. B. infantis absolute abundance started low at birth but increased in the first two months, whereas B. longum and B. breve abundances remained comparatively low. B. infantis emerged earlier in infants delivered by C-section, but by ~2 months of age, infants delivered by C-section or vaginally had similar B. infantis absolute abundances. Infant antibiotic exposure (ever vs. never), human milk feeding patterns (exclusive, predominant, and partial), and detection of maternal stool B. infantis were not associated with infant B. infantis. In settings where B. infantis is widespread, its patterns of postnatal colonization can be used to inform the design of targeted microbiota-modifying interventions in infancy.IMPORTANCEBifidobacteria are considered to be an important member of the early infant gut microbiota, but several factors may influence the timing of their emergence and overall abundance. Moreover, bifidobacteria abundance varies considerably between different species and subspecies, underscoring the importance of techniques that enable sub-speciation. B. longum subspecies infantis (B. infantis) is thought to have several health-promoting properties, and despite growing interest in the use of B. infantis to promote health (e.g., probiotics), relatively few studies have explored its natural patterns of colonization, particularly in low- and middle-income countries. By applying (sub)species-specific qPCR, we precisely tracked the timing of emergence, longitudinal abundance patterns, and ecological dynamics of B. infantis, B. longum, and B. breve in the postnatal period, which provided new insights to inform the design of targeted microbiota-modifying interventions in early infancy.

OBJECTIVES:Length-for-age z-scores (LAZ) and stunting prevalence (%LAZ <-2) are commonly used to quantify linear growth faltering in young children in low- and middle-income countries (LMICs). The Healthy Birth, Growth and Development knowledge integration (HBGDki) consortium described postnatal linear growth faltering using LAZ-by-age trajectory modelling and child-level LAZ threshold-crossing events, including incident stunting onset (first occurrence of LAZ <-2) and stunting reversal (LAZ rising from <-2 to ≥-2). Using simulations, we assessed the suitability of these LAZ threshold-crossing metrics for characterising linear growth faltering in LMICs. METHODS:We simulated a synthetic cohort with a harmonically downward-shifting LAZ trajectory from birth to 24 months of age, with mean LAZs similar to the HBGDki pooled South Asian cohorts, and without any input parameters intended to differentially affect individuals' growth across the height distribution or at different ages. We compared HBGDki empirical estimates of age interval-specific frequencies of incident stunting onset and stunting reversal with those from the synthetic cohort. Using synthetic cohorts, we examined how estimates of incident onset and reversal were affected by missing data, magnitude of the whole-population shift in the LAZ distribution and strength of the between-time-point correlation. We also compared the 3-24 month pattern of linear growth faltering expressed as age-related trajectories of average growth delay (chronological age minus height-age), mean LAZ or stunting prevalence. RESULTS:Empirical estimates of age interval-specific incident stunting onset and stunting reversal in the HBGDki cohorts were similar to those observed in a synthetic cohort. Variability in LAZ threshold-crossing event rates is explained by starting LAZ, between-time-point correlation and the magnitude of the whole-population shift in the LAZ distribution. Incident stunting onset is also affected by missing data in preceding intervals. Stunting reversal occurs due to within-child variability (ie, imperfect between-time-point correlation) in the absence of any other phenomena that cause stunted children to become non-stunted at a later age. The linear growth faltering pattern based on growth delay differed from corresponding age-related trajectories of mean LAZ or stunting prevalence. CONCLUSIONS:In longitudinal studies of linear growth faltering in LMICs, LAZ threshold-crossing indicators are byproducts of whole-population shifts in LAZ and within-child variability and should be interpreted accordingly. Reporting incident stunting onset and reversal rates, or analyses in which children are grouped by the timing of LAZ threshold-crossing events, may detract from efforts to understand when and why nearly all children in LMICs grow more slowly than expected for their age. Since mean LAZ and stunting prevalence are unsuitable for quantifying the rate and timing of population-average postnatal linear growth faltering, growth delay is recommended for consideration as a preferred metric.

Background: Lactobacillus probiotics may enhance host iron bioavailability, offering a potential strategy to address iron deficiency; however, evidence of such effects in infants is lacking. Objective: To examine whether neonatal administration of Lactiplantibacillus plantarum ATCC 202195 (LP202195), with or without fructooligosaccharide (FOS), reduces stool iron content and improves iron status in young infants in Dhaka, Bangladesh. Methods: This study was a secondary analysis of a randomized placebo-controlled trial in which infants, 0-4 days of age, were randomly allocated to one of five groups: placebo, 1- or 7-day regimens of LP202195, with or without FOS. Fecal iron was quantified in stool samples collected at 14 days postnatal age (n=307) and serum ferritin concentration was measured at 2 months postnatal age (n= 251). Effects of the 1- and 7-day LP202195 regimens were estimated using linear regression and reported as mean percent differences relative to placebo, with 95% confidence intervals (95%CI). Results: In the combined analysis irrespective of FOS co-administration, there were no differences in fecal iron concentrations following 1-day (% difference=9.8%, 95%CI: -19%, 49%; P=0.54) or 7-days (% difference= -6.1%, 95%CI: -31%, 28%; P=0.69) of LP202195 administration, relative to placebo (geometric mean concentration=4.3mg Fe/100g dry stool (95%CI:3.3, 5.6); n=53). There were no effects of LP202195 administration on serum ferritin concentration following the 1-day (% difference=2.4%, 95%CI: -22%, 35%; P=0.86) or 7-day (% difference=1%, 95% CI: -23%, 33%; P=0.94) regimen, relative to placebo (geometric mean concentration=189 ng/mL (95%CI: 155, 232); n=55). Inferences were unchanged when intervention groups were disaggregated by FOS co-administration (P>0.05 for all). Conclusions: LP202195, when administered neonatally as a probiotic alone or synbiotic with FOS for 1 or 7 days, did not affect stool iron (2 weeks of age) or iron status (2 months of age) in Dhaka, Bangladesh. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial ClinicalTrials.gov identifier: [NCT05180201][1] ### Funding Statement This work was supported by The Bill & Melinda Gates Foundation (INV-007389 and GR-02268). The funders had no role in the design or implementation of the study, or the analyses, interpretation of findings, and the decision to publish the results. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study was a sub-study of a randomized, placebo-controlled trial involving neonatal oral administration of LP202195, with or without FOS, for 1- or 7-days, which was approved by the ethical review committees at International Centre for Diarroheal Disease Research, Bangladesh (icddr,b) (ERC protocol no. PR-20139), the Bangladesh Institute of Child Health, Dhaka Shishu Hospital, the ethical governing body for the Child Health Research Foundation (ERC protocol no. BICH-ERC-02-02-2019), the Directorate General of Drug Administration (DGDA), Bangladesh (DGDA/CTP-04/2016/672), and the Research Ethics Board at The Hospital for Sick Children, Toronto, Canada (REB no. 1000072200). Additionally, ethical approval was also obtained for this sub-study from the ethical review committees at icddr,b (ERC protocol no. PR-21099), and the Research Ethics Board at The Hospital for Sick Children, Toronto, Canada (REB no. 1000078635). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes De-identified data, code files, and all additional information required to reanalyze the data presented in this manuscript have been deposited at Borealis, The Canadian Dataverse Repository and will be made publicly available as of the date of publication. https://doi.org/10.5683/SP3/RJUT53 [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT05180201&atom=%2Fmedrxiv%2Fearly%2F2025%2F09%2F28%2F2025.09.25.25336651.atom

Infant undernutrition, defined by length- and weight-based indices, is common in low- and middle-income countries (LMICs), but corresponding deficits in head size have received less attention. In a cohort of term newborns in Dhaka, Bangladesh, we compared the severity of deficits (vs. World Health Organization Growth Standards) in head circumference (HC), length and weight at birth and every 3 months until 2 years of age (n range across timepoints: 843-920). We estimated the mean and 25th, 50th and 75th percentiles of HC-, length- and weight-for-age z-scores (HCZ, LAZ and WAZ, respectively). Differences between HCZ and LAZ (or WAZ) were analyzed using paired t tests and quantile regression. We also derived HCZ using height-age instead of chronological age at 3-24 months. Mean HCZ was significantly higher than mean LAZ and WAZ at birth, but HCZ was significantly lower than LAZ at 6, 9 and 12 months and the HCZ and LAZ deficits were similar from 15 to 24 months. Mean HCZ was lower than WAZ at all ages beyond birth. Patterns were broadly consistent at the 25th, 50th and 75th percentiles. The HCZ deficit remained evident when HC was standardized using height-age at all ages beyond birth, indicating HC was reduced relative to body size. In conclusion, among term-born children in Dhaka, HCs were smaller than international standards at all ages up to 2 years, and there was no evidence of postnatal head sparing. Consideration should be given to routine measurement of HC in population health surveys in LMICs.

Background:Assessments of the efficacy of interventions to improve child growth are often based on differences in mean height-for-age z-scores (HAZ) and stunting (HAZ<-2) in randomized controlled trials (RCTs). However, this approach does not account for children's starting skeletal age and does not enable assessment of the extent to which interventions optimized linear growth. Objectives:The objectives of this study were to develop and apply a new method using height-age to express linear growth effects in RCTs. Methods:Longitudinal individual participant data (IPD) from a Bangladeshi trial cohort were used to compare height-age estimates derived from individual-level heights, mean raw height, or mean HAZ. Then, using mean height-age as a proxy for skeletal age, we developed the "proportion of maximal benefit" (PMB) metric to quantify intervention effects relative to optimal growth for children's starting skeletal age. Optimal growth occurs when height-age increases in parallel with chronologic age (i.e., PMB = 100%), whereas no effect (compared with control) corresponds to a PMB of 0%. Linear growth outcomes in 4 published RCTs of nutrition-specific interventions were re-expressed as mean height-age and PMB and compared with effects conventionally expressed as intervention-compared with-control mean differences (MD) in HAZ. Results:Mean height-age could be derived from any published estimate of mean raw height or mean HAZ; however, to calculate the PMB, height or HAZ data were required at both the beginning and end of the observation period. Interpretations of intervention effects were consistent when expressed as either the height-age MD or HAZ MD. In contrast, the PMB does not have a corresponding metric on the HAZ scale and, therefore, provided a new way to quantify intervention efficacy. Conclusions:Height-age can be used as an alternative to HAZ to express intervention effects. The PMB has the advantage of conveying the extent to which an intervention improved average linear growth in relation to a biologically-defined benchmark.

ABSTRACT Background Copper (Cu), an essential trace mineral regulating multiple actions of inflammation and oxidative stress, has been implicated in risk for preterm birth (PTB). We aimed to determine the association of maternal plasma/serum Cu concentrations during pregnancy with PTB risk and gestational duration in a large multi-cohort study including diverse populations. Methods Gestational duration data and maternal plasma or serum samples of 10,449 singleton live births were obtained from 18 geographically diverse study cohorts. Maternal plasma or serum Cu concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS) analysis. The associations of maternal Cu with PTB and gestational duration were analyzed using logistic and linear regressions for each cohort. The estimates were then combined using meta-analysis. Associations between maternal Cu and acute phase reactants (APRs), malaria, and HIV infection were analyzed in 1239 samples from the Malawi cohort. Findings The maternal prenatal Cu concentration in our study samples followed a normal distribution with a mean of 1.92 μg/ml and a standard deviation of 0.43 μg/ml, and Cu concentrations increased with gestational age up to 20 weeks. The random effect meta-analysis across the 18 cohorts revealed that 1 μg/ml increase in maternal Cu concentration before the third trimester was associated with a higher risk of PTB with an OR of 1.30 (95% CI: 1.08 to 1.57) and shorter gestational duration of 1.64 days (95% CI: 0.56 to 2.73). The estimated effects were generally consistent across all sites. In the Malawi cohort, higher maternal Cu concentration, concentrations of multiple APRs and infections (malaria and HIV) were correlated and associated with greater risk of PTB and shorter gestational duration. Interpretation Our study supports a robust negative association between maternal mid-gestation Cu concentration and gestational duration and a positive association with risk for preterm birth. Cu concentration was strongly correlated with APRs and infection status suggesting its potential role in inflammation, a pathway implicated in the mechanisms of PTB. Therefore, maternal Cu could be used as a potential marker of the integrated inflammatory pathways during pregnancy and risk for preterm birth.

Linear growth faltering (LGF), or slower than normal growth in height, is widely considered an indicator of suboptimal conditions affecting children’s development and health in low- and middle-income countries (LMICs). Recently, Benjamin-Chung and collaborating members of the Healthy Birth, Growth and Development Knowledge integration (HBGDki) consortium described the early onset and low reversal rates of LGF in 32 cohort studies that followed over 52,000 children from birth to 24 months of age in 14 countries. Their adoption and extension of conventionally used growth metrics to describe faltering patterns led to findings that echo a long-standing assumption that LGF in resource-constrained settings occurs mainly during early infancy and is mostly irreversible thereafter. Here, we discuss limitations of their methods and suggest an alternative approach that leads to different conclusions about the rate and timing of LGF in LMICs.

Vitamin D is a key regulator of bone mineral homeostasis and may modulate maternal bone health during pregnancy and postpartum. Using previously-collected data from the Maternal Vitamin D for Infant Growth (MDIG) trial in Dhaka, Bangladesh, we aimed to investigate the effects of prenatal and postpartum vitamin D3 supplementation on circulating biomarkers of bone formation and resorption at delivery and 6 months postpartum. MDIG trial participants were randomized to receive a prenatal;postpartum regimen of placebo or vitamin D3 (IU/week) as either 0;0 (Group A), 4200;0 (B), 16,800;0 (C), 28,000;0 (D) or 28,000;28,000 (E) from 17 to 24 weeks' gestation to 6 months postpartum. As this sub-study was not pre-planned, the study sample included MDIG participants who had data for at least 1 biomarker of interest at delivery or 6 months postpartum, with a corresponding baseline measurement (n = 690; 53 % of 1300 enrolled trial participants). Biomarkers related to bone turnover were measured in maternal venous blood samples collected at enrolment, delivery, and 6 months postpartum: osteoprotegerin (OPG), osteocalcin (OC), receptor activator nuclear factor kappa-B ligand (RANKL), fibroblast growth factor 23 (FGF23), procollagen type 1 N-terminal propeptide, (P1NP) and carboxy terminal telopeptide of type 1 collagen (CTx). Supplementation effects were expressed as percent differences between each vitamin D group and placebo with 95 % confidence intervals (95 % CI). Of 690 participants, 64 % had 25-hydroxyvitamin D concentrations (25OHD) <30 nmol/L and 94 % had 25OHD < 50 nmol/L at trial enrolment. At delivery, mean CTx concentrations were 27 % lower in group E versus placebo (95 % CI: −38, −13; P < 0.001), adjusting for enrolment concentrations. However, at 6 months postpartum, CTx concentrations were not statistically different in group E versus placebo (14 %; 95 % CI: −5.3, 37; P = 0.168), adjusting for delivery CTx concentrations. Effects on other biomarkers at delivery or postpartum were not statistically significant. In conclusion, prenatal high-dose vitamin D supplementation reduced bone resorption during pregnancy, albeit by only one biomarker, and without evidence of a sustained effect in the postpartum period. However, further evidence is needed to substantiate potential maternal bone health benefits of vitamin D in the postpartum period.

OBJECTIVE:Growth faltering is widespread in many low- and middle-income countries, but its effects on childhood bone mass accrual are unknown. The objective of this study was to estimate associations between length (conditional length-for-age z-scores, cLAZ) and weight (conditional weight-for-age z-scores, cWAZ) gain in three age intervals (ages 0-6, 6-12 and 12-24 months) with dual-energy X-ray absorptiometry-derived measures of bone mass (total body less head (TBLH) bone mineral content (BMC), areal bone mineral density (aBMD) and bone area) at 4 years of age. DESIGN:Associations between interval-specific growth parameters (cLAZ and cWAZ) and bone outcomes were estimated using linear regression models, adjusted for maternal, child and household characteristics. SETTING:Data collection occurred in Dhaka, Bangladesh. PARTICIPANTS:599 healthy children enrolled in the BONe and mUScle Health in Kids Study. RESULTS:cLAZ in each age interval was positively associated with TBLH BMC, aBMD and bone area at 4 years; however, associations attenuated towards null upon adjustment for concurrent height-for-age z-scores (HAZ) at age 4 years and confounders. cWAZ from 0 to 6 and 6 to 12 months was not associated with bone mass, but every sd increase in cWAZ between 12 and 24 months was associated with greater BMC (7·6 g; 95 % CI: 3·2, 12·0) and aBMD (0·008 g/cm2; 95 % CI: 0·003, 0·014) after adjusting for concurrent WAZ, HAZ and confounders. CONCLUSIONS:Associations of linear growth (birth to 2 years) with bone mass at age 4 years were explained by concurrent HAZ. Weight gain in the second year of life may increase bone mass independently of linear growth in settings where growth faltering is common.

BACKGROUND The use of high-throughput technologies has enabled rapid advancement in the knowledge of host immune responses to pathogens. Our objective was to compare the repertoire, protection, and maternal factors associated with human milk antibodies to infectious pathogens in different economic and geographic locations.METHODS Using multipathogen protein microarrays, 878 milk and 94 paired serum samples collected from 695 women in 5 high and low-to-middle income countries (Bangladesh, Finland, Peru, Pakistan, and the United States) were assessed for specific IgA and IgG antibodies to 1,607 proteins from 30 enteric, respiratory, and bloodborne pathogens.RESULTS The antibody coverage across enteric and respiratory pathogens was highest in Bangladeshi and Pakistani cohorts and lowest in the U.S. and Finland. While some pathogens induced a dominant IgA response (Campylobacter, Klebsiella, Acinetobacter, Cryptosporidium, and pertussis), others elicited both IgA and IgG antibodies in milk and serum, possibly related to the invasiveness of the infection (Shigella, enteropathogenic E. coli “EPEC”, Streptococcus pneumoniae, Staphylococcus aureus, and Group B Streptococcus). Besides the differences between economic regions and decreases in concentrations over time, human milk IgA and IgG antibody concentrations were lower in mothers with high BMI and higher parity, respectively. In Bangladeshi infants, a higher specific IgA concentration in human milk was associated with delayed time to rotavirus infection, implying protective properties of antirotavirus antibodies, whereas a higher IgA antibody concentration was associated with greater incidence of Campylobacter infection.CONCLUSION This comprehensive assessment of human milk antibody profiles may be used to guide the development of passive protection strategies against infant morbidity and mortality.FUNDING Bill and Melinda Gates Foundation grant OPP1172222 (to KMJ); Bill and Melinda Gates Foundation grant OPP1066764 funded the MDIG trial (to DER); University of Rochester CTSI and Environmental Health Sciences Center funded the Rochester Lifestyle study (to RJL); and R01 AI043596 funded PROVIDE (to WAP).

BACKGROUND:The role of maternal vitamin D supplementation in the prevention of infantile rickets is unknown, particularly in low- and middle-income countries without routine infant vitamin D supplementation. Through secondary analysis of a randomized, placebo-controlled trial in Bangladesh, we examined the dose-ranging effects of maternal vitamin D supplementation on the risk of biochemical rickets at 6 to 12 months of age. METHODS:Pregnant women (n = 1300) were randomized into 5 groups: placebo, or vitamin D 4200 IU/week, 16 800 IU/week, or 28 000 IU/week from second trimester to delivery and placebo until 6 months postpartum; or 28 000 IU/week prenatally and until 6 months postpartum. Infants underwent biochemical rickets screening from 6 to 12 months of age (n = 790). Relative risks (RR) and 95% confidence intervals (95% CI) of biochemical rickets were estimated for each group versus placebo. RESULTS:Overall, 39/790 (4.9%) infants had biochemical rickets. Prevalence was highest in the placebo group (7.8%), and the risk was significantly lower among infants whose mothers received combined prenatal and postpartum vitamin D at 28 000 IU/week (1.3%; RR, 0.16; 95% CI, 0.03-0.72). Risks among infants whose mothers received only prenatal supplementation (4200 IU, 16 800 IU, 28 000 IU weekly) were not significantly different from placebo: 3.8% (RR, 0.48; 95% CI, 0.19-1.22), 5.8% (RR, 0.74; 95% CI, 0.33-1.69), and 5.7% (RR, 0.73; 95% CI, 0.32-1.65), respectively. CONCLUSIONS:Maternal vitamin D supplementation (28 000 IU/week) during the third trimester of pregnancy until 6 months postpartum reduced the risk of infantile biochemical rickets. Further research is needed to define optimal postpartum supplementation dosing during lactation.

BackgroundEmerging evidence suggests that clinical prediction models that use repeated (time-varying) measurements within each patient may have higher predictive accuracy than models that use patient information from a single measurement.ObjectiveTo determine the breadth of the published literature reporting the development of clinical prediction models in children that use time-varying predictors.Data sourcesMEDLINE, EMBASE and Cochrane databases.Eligibility criteriaWe included studies reporting the development of a multivariable clinical prediction model in children, with or without validation, to predict a repeatedly measured binary or time-to-event outcome and utilizing at least one repeatedly measured predictor.Synthesis methodsWe categorized included studies by the method used to model time-varying predictors.ResultsOf 99 clinical prediction model studies that had a repeated measurements data structure, only 27 (27%) used methods that incorporated the repeated measurements as time-varying predictors in a single model. Among these 27 time-varying prediction model studies, we grouped model types into nine categories: time-dependent Cox regression, generalized estimating equations, random effects model, landmark model, joint model, neural network, K-nearest neighbor, support vector machine and tree-based algorithms. Where there was comparison of time-varying models to single measurement models, using time-varying predictors improved predictive accuracy.ConclusionsVarious methods have been used to develop time-varying prediction models in children, but there is a paucity of pediatric time-varying models in the literature. Incorporating time-varying covariates in pediatric prediction models may improve predictive accuracy. Future research in pediatric prediction model development should further investigate whether incorporation of time-varying covariates improves predictive accuracy.What this Scoping Review AddsOf 99 clinical prediction model studies that had a repeated measurements data structure, only 27% used analytical methods that incorporated time-varying covariates. Future research in pediatric prediction model development should further investigate whether incorporation of time-varying covariates improves predictive accuracy.How to Use this Scoping ReviewWe summarized methods used to develop pediatric clinical prediction models that incorporate repeated measurements with time-varying covariates. Researchers may use the findings of this review to identify appropriate analytical methods for developing a time-varying prediction model in pediatric care.