Heavy prenatal alcohol exposure is associated with changes to the brain’s white matter, which may underpin attention problems observed in this population. Less is known about the effect of low to moderate exposure. This study investigated white matter correlates of attention in children with low to moderate levels of prenatal alcohol exposure and controls whose mothers abstained from alcohol. We also examined whether associations differed between alcohol exposure in trimester one only or throughout pregnancy. A total of 129 children aged 6-7-years from the prospective Asking Questions about Alcohol in pregnancy (AQUA) cohort (trimester one alcohol exposure n = 47; exposure throughout pregnancy n = 45; controls n = 37) participated in a brain magnetic resonance imaging study. Fixel-based analysis was performed on diffusion weighted images to investigate associations between whole brain white matter micro- and macro-structure and attention (focus, shift, sustain, hyperactivity and inattention). In controls, better focused attention and less hyperactivity were associated with greater macrostructural cross-sectional area of the corticospinal tract and cerebellar white matter, respectively. Greater microstructural fiber density in the splenium of the corpus callosum was associated with more inattention in the children with trimester one alcohol exposure, which persisted when adjusted for any binge drinking episodes prior to pregnancy recognition. Subtle differences in the association between white matter and attention were found between controls and prenatal exposure groups, where associations were stronger in controls. While further exploration is needed, preliminary findings in 6-7-year-old children suggest that low to moderate prenatal alcohol exposure affects white matter fibers that subserve attention skills.

Importance In addition to confirmed prenatal alcohol exposure and severe neurodevelopmental deficits, three cardinal facial features are included in the diagnostic criteria for fetal alcohol spectrum disorder. It is not understood whether subtle facial characteristics occur in children without a diagnosis but who were exposed to a range of common pregnancy drinking patterns and, if so, whether these persist throughout childhood. Objective To determine whether subtle changes in facial shape with prenatal alcohol exposure found in 12-month-old children were evident at age 6 to 8 years using extended phenotyping methods and, if so, whether facial characteristics were similar to those seen in fetal alcohol spectrum disorder. Design, Setting, and Participants In a prospective cohort study in Melbourne, Victoria, Australia, commencing in July 2011 with follow-up through April 2021, pregnant women were recruited in the first trimester from low-risk, metropolitan, public maternity clinics over a period of 12 months. Three-dimensional craniofacial images from 549 children of European descent taken at age 12 months (n = 421 images) and 6 to 8 years (n = 363) were included. Data analysis was performed from May 2021 to October 2024. Exposures Predominantly low to moderate prenatal alcohol exposure in the first trimester or throughout pregnancy compared with controls without prenatal alcohol exposure. Main Outcomes and Measures Following hierarchical facial segmentation, phenotype descriptors were computed. Hypothesis testing was performed for 63 facial modules to analyze different facial parts independently using principal component analysis and response-based imputed predictor (RIP) scores. Comparison was made with a clinical discovery sample of facial images of children with a confirmed diagnosis of partial or full fetal alcohol syndrome. Results A total of 549 children took part in the 3-dimensional craniofacial image analysis, of whom 235 (42.8%) contributed an image at both time points. Time 1 included 421 children, comprising 336 children (159 [47.3%] female) with any prenatal alcohol exposure and 85 control children (45 [52.9%] female); time 2 included 363 children, comprising 260 children with any prenatal alcohol exposure (125 [48.1%] female; mean [SD] age, 6.9 [0.7] years) and 103 control children (53 [51.5%] female; mean [SD] age, 6.8 [0.7] years). At both time points, there was consistent evidence for an association between prenatal alcohol exposure and the shape of the eyes (eg, module 15: RIP partial Spearman ρ, 0.19 [95% CI, 0.10-0.29; P < .001] at 6-8 years) and nose (eg, module 5: RIP partial Spearman ρ, 0.19 [95% CI, 0.09-0.27; P < .001] at 6-8 years), whether exposure occurred only in trimester 1 or throughout pregnancy. Facial variations observed differed from those in the clinical discovery sample. Conclusions and Relevance Low to moderate prenatal alcohol exposure was associated with characteristic changes in the face, which persisted until at least 6 to 8 years of age. A linear association between alcohol exposure levels and facial shape was not supported.

Research question: What are the health outcomes of individuals aged 27-38 years conceived with and without assisted reproductive technology (ART)? Design: An online survey, hosted in REDCap, was used to collect information on self-reported physical, psychological and reproductive health from an established cohort of people conceived with and without ART who were now aged 27-38 years. Questions included lists of common conditions and required tick-box responses to determine prevalence. A validated scale was used to assess psychological well-being. Results: There were 313 ART-conceived (236 IVF and 77 gamete intrafallopian transfer [GIFT]) and 153 non-ART conceived respondents. No marked differences between the ART and non-ART groups were observed in physical or psychological health measures. Similar proportions in both groups had had children and reported using medically assisted reproduction to conceive. More women in the ART than the non-ART group reported at least one reproductive health disorder (P = 0.01). Male reproductive health disorders were rare in both groups. Conclusions: Subjective indicators of health were no different between ART-and non-ART-conceived individuals, except for a slight increase in adverse reproductive health disorders reported by ART-conceived female participants. This warrants closer clinical scrutiny. Overall, a larger sample and objective measures in individuals beyond 30 years of age would provide the ultimate reassurance that ART is not associated with long-term health problems. This study is the first of its kind and may provide some reassurance of safety for people conceived with ART and those who contemplate using it.

(Abstracted from N Engl J Med 2024;391:1877–1889) Couple-based genetic carrier screening analyzes parental genetic samples before or early in pregnancy to assess the risk of autosomal and X-linked recessive diseases in their children. Previously, carriers were often unidentified until after having an affected child but advances in sequencing now allow simultaneous screening across thousands of genes, giving prospective parents greater insight into their risk.

Purpose:The long-term developmental outcomes of children with a prenatal diagnosis of a copy-number variant of uncertain significance (VUS) remain unclear. This study compared the developmental, social-emotional, and health outcomes of children with and without a prenatal VUS, assessed maternal perceptions of their child's health and development, and examined the reclassification rate of VUS after more than 2 years. Methods:Women who underwent prenatal chromosomal microarray testing in Victoria, Australia (2013-2019), were recruited retrospectively (2021-2023). Children with a VUS (cases) were compared with controls without a VUS. We assessed a range of cognitive, developmental, and health outcomes in the children, who were on average 6 years old. Statistical analyses compared group outcomes and adjusted for maternal sociodemographic factors. Results:The study included 134 mother-child pairs (46 with a VUS and 88 controls). No significant differences were found between groups in intellectual functioning, adaptive behavior, or social-emotional measures. Maternal perceptions of their child and family well-being were also similar. Reanalysis reclassified 66.0% of VUS as benign and 8.5% as pathogenic. Conclusion:Children with a prenatal VUS diagnosis have developmental outcomes and family well-being comparable to those without. These findings contribute valuable evidence to support prenatal genetic counseling and clinical laboratory reporting practices.

Abstract Background There are no established guidelines for the follow up of infants born after a prenatal diagnosis of a genomic copy number variant (CNV), despite their increased risk of developmental issues. The aims of this study were (i) to determine the perinatal outcomes of fetuses diagnosed with and without a CNV, and (ii) to establish a population-based paediatric cohort for long term developmental follow up. Methods An Australian state-wide research database was screened for pregnant individuals who had a prenatal chromosomal microarray (CMA) between 2013–2019 inclusive. Following linkage to laboratory records and clinical referrer details, hospital records were manually reviewed for study eligibility. Eligible participants were mother–child pairs where the pregnancy resulted in a livebirth, the mother was able to provide informed consent in English (did not require a translator) and the mother was the primary caregiver for the child at hospital discharge after birth. Research invitations were sent by registered post at an average of six years after the prenatal diagnostic test. Statistical analysis was performed in Stata17. Results Of 1832 prenatal records examined, 1364 (74.5%) mother–child pairs were eligible for recruitment into the follow up cohort. Of the 468 ineligible, 282 (60.3%) had ‘no live pregnancy outcome’ (209 terminations of pregnancy (TOP) and 73 miscarriages, stillbirths, and infant deaths), 157 (33.5%) required a translator, and 29 (6.2%) were excluded for other reasons. TOP rates varied by the type of fetal CNV detected: 49.3% (109/221) for pathogenic CNVs, 18.2% (58/319) for variants of uncertain significance and 3.3% (42/1292) where no clinically significant CNV was reported on CMA. Almost 77% of invitation letters were successfully delivered (1047/1364), and the subsequent participation rate in the follow up cohort was 19.2% (201/1047). Conclusions This study provides Australia’s first population-based data on perinatal outcomes following prenatal diagnostic testing with CMA. The relatively high rates of pregnancy loss for those with a prenatal diagnosis of a CNV presented a challenge for establishing a paediatric cohort to examine long term outcomes. Recruiting a mother–child cohort via prenatal ascertainment is a complex and resource-intensive process, but an important step in understanding the impact of a CNV diagnosis in pregnancy and beyond. Trial registration ACTRN12620000446965p; Registered on April 6, 2020.

Evidence is strong for adverse fetal effects of high level or chronic prenatal alcohol exposure (PAE), but many pregnant women continue to drink at lower levels. The ‘Asking Questions about Alcohol in pregnancy’ prospective cohort aimed to determine the neurodevelopmental consequences at 6–8 years of age of low to moderate PAE. 1570 women from seven public antenatal clinics in Melbourne, Australia, provided information on frequency and quantity of alcohol use, and obstetric, lifestyle and socio-environmental confounders at four gestation timepoints. PAE was classified into five trajectories plus controls. At 6–8 years, 802 of 1342 eligible families took part and completed a questionnaire (60%) and 696 children completed neuropsychological assessments (52%). Multiple linear regressions examined mean outcome differences between groups using complete case and multiple imputation models. No meaningful relationships were found between any of the PAE trajectories and general cognition, academic skills, motor functioning, behaviour, social skills, social communication, and executive function. Maternal education most strongly influenced general cognition and academic skills. Parenting behaviours and financial situation were associated with academic skills, behaviour, social skills and/or executive function. The lack of association between PAE and neurodevelopment at 6–8 years may partly be explained by cumulative positive effects of socio-environmental factors.

Background Genomic sequencing technology allows for identification of reproductive couples with an increased chance, as compared with that in the general population, of having a child with an autosomal recessive or X-linked genetic condition. Methods We investigated the feasibility, acceptability, and outcomes of a nationwide, couple-based genetic carrier screening program in Australia as part of the Mackenzie's Mission project. Health care providers offered screening to persons before pregnancy or early in pregnancy. The results obtained from testing at least 1281 genes were provided to the reproductive couples. We aimed to ascertain the psychosocial effects on participants, the acceptability of screening to all participants, and the reproductive choices of persons identified as having an increased chance of having a child with a condition for which we screened. Results Among 10,038 reproductive couples enrolled in the study, 9107 (90.7%) completed screening, and 175 (1.9%) were newly identified as having an increased chance of having a child with a genetic condition for which we screened. These conditions involved pathogenic variants in 90 different genes; 74.3% of the conditions were autosomal recessive. Three months after receiving the results, 76.6% of the couples with a newly identified increased chance had used or planned to use reproductive interventions to avoid having an affected child. Those newly identified as having an increased chance had greater anxiety than those with a low chance. The median level of decisional regret was low in all result groups, and 98.9% of participants perceived screening to be acceptable. Conclusions Couple-based reproductive genetic carrier screening was largely acceptable to participants and was used to inform reproductive decision making. The delivery of screening to a diverse and geographically dispersed population was feasible. (Funded by the Medical Research Future Fund of the Australian government; ClinicalTrials.gov number, NCT04157595.) A Nationwide Couple-Based Genetic Screen In this study, 77% of couples identified as having an increased risk of having a child with an autosomal recessive or X-linked condition used or planned to use reproductive interventions.

Background: The effects of low-moderate prenatal alcohol exposure (PAE) on brain development have been infrequently studied. Aim: To compare cortical and white matter structure between children aged 6 to 8 years with low-moderate PAE in trimester 1 only, low-moderate PAE throughout gestation, or no PAE. Methods: Women reported quantity and frequency of alcohol consumption before and during pregnancy. Magnetic resonance imaging was undertaken for 143 children aged 6 to 8 years with PAE during trimester 1 only (n = 44), PAE throughout gestation (n = 58), and no PAE (n = 41). T-1-weighted images were processed using FreeSurfer, obtaining brain volume, area, and thickness of 34 cortical regions per hemisphere. Fibre density (FD), fibre cross-section (FC) and fibre density and cross-section (FDC) metrics were computed for diffusion images. Brain measures were compared between PAE groups adjusted for age and sex, then additionally for intracranial volume. Results: After adjustments, the right caudal anterior cingulate cortex volume (p(FDR) = 0.045) and area (p(FDR) = 0.008), and right cingulum tract cross-sectional area (p(FWE) < 0.05) were smaller in children exposed to alcohol throughout gestation compared with no PAE. Conclusion: This study reports a relationship between low-moderate PAE throughout gestation and cingulate cortex and cingulum tract alterations, suggesting a teratogenic vulnerability. Further investigation is warranted.

Alcohol consumption in pregnancy can affect genome regulation in the developing offspring but results have been contradictory. We employed a physiologically relevant murine model of short-term moderate prenatal alcohol exposure (PAE) resembling common patterns of alcohol consumption in pregnancy in humans. Early moderate PAE was sufficient to affect site-specific DNA methylation in new-born pups without altering behavioural outcomes in adult littermates. Whole-genome bisulfite sequencing of neonatal brain and liver revealed stochastic influence on DNA methylation that was mostly tissue-specific, with some perturbations likely originating as early as gastrulation. DNA methylation differences were enriched in non-coding genomic regions with regulatory potential indicative of broad effects of alcohol on genome regulation. Replication studies in human cohorts with fetal alcohol spectrum disorder suggested some effects were metastable at genes linked to disease-relevant traits including facial morphology, intelligence, educational attainment, autism, and schizophrenia. In our murine model, a maternal diet high in folate and choline protected against some of the damaging effects of early moderate PAE on DNA methylation. Our studies demonstrate that early moderate exposure is sufficient to affect fetal genome regulation even in the absence of overt phenotypic changes and highlight a role for preventative maternal dietary interventions.

Almost half of infertility cases involve male infertility. Understanding the consequence of a diagnosis of male infertility, as a sole or partial contributor to the couples' infertility, to the mental health of men is required to ensure clinical care meets their psychological needs. The aim of this systematic analysis was to synthesize the evidence regarding whether men diagnosed with male factor infertility experience greater psychological distress than (1) men described as fertile and (2) men in couples with other infertility diagnoses. Online databases were searched using a combination of Medical Subject Headings (MeSH) headings and keywords relating to male infertility and psychological distress. The search yielded 1016 unique publications, of which 23 were included: 8 case-control, 14 prospective cohort, and 1 data linkage studies. Seven aspects of psychological distress were identified depression, anxiety, self-esteem, quality of life, fertility-related stress, general psychological stress or well-being, and psychiatric conditions. Case-control studies reported that men with male factor infertility have more symptoms of depression, anxiety and general psychological distress, worse quality of some aspects of life, and lower self-esteem than controls. When men with male factor infertility were compared to men in couples with other causes of infertility, there were few differences in the assessed aspects of psychological distress. Despite methodological limitations within the studies, this systematic analysis suggests that the experience of infertility, irrespective of its cause, negatively affects men's mental health and demonstrates the need for assisted reproduction technology (ART) providers to consider men undergoing assisted reproduction as individuals with their own unique support needs.

Prenatal screening for aneuploidy has undergone immense changes over the past two decades. In 2013 cell‐free DNA‐based non‐invasive prenatal testing (NIPT) became a new self‐funded option primarily for Down syndrome screening, but also other aneuploidies and genetic conditions. The numbers of Medicare item claims for prenatal diagnostic procedures have halved since the introduction of NIPT, while billings for serum screening fell by 40% over the same period, on a background of steady births. Australia is now observing historically low rates of prenatal diagnostic testing. These data provide an informative snapshot of historic changes in prenatal screening and diagnosis, as our sector prepares for the impending impacts of other advances in genomics on maternity care. They also highlight the need to address equity and quality issues that arise when consumers must bear the full costs of improved genomic tests in the absence of Medicare funding.

Assisted Reproductive Technologies (ARTs) have resulted in more than 8 million births since 1978. Compared with spontaneously conceived babies, ART-conceived babies are at an increased risk of preterm birth, low birth weight, being small or large for gestational age, congenital anomalies, and perinatal mortality. Early studies showed that ART conception was associated with a higher incidence of rare imprinted disorders, stimulating interest in assessing epigenetic variation associated with ART and linking this variation to poor perinatal outcomes. In this chapter, we summarize the current state of the epigenetic and ART field in humans. We focus on epigenome-wide association studies of human blood at birth and address the temporal, cell-type–specific, and ART-component–specific findings. In recent years, studies have begun to replicate specific DNA methylation changes associated with ART. The next phase of research will be to explain how these epigenetic differences arise and whether they mediate the adverse perinatal outcomes observed in ART pregnancies.

ObjectiveTo determine the perinatal outcomes of fetuses diagnosed with a pathogenic copy number variant (CNV) or variant of uncertain significance (VUS); and to characterize these variants in terms of testing indication, genomic location, size, and inheritance. MethodsRetrospective study of singleton pregnancies with a pathogenic CNV or VUS from a single laboratory during 2012-2018. Probabilistic record linkage between the prenatal diagnosis dataset and perinatal outcome data for births from 20 weeks gestation was performed. If no birth record was found, this implied a pregnancy loss We included 6945 prenatal microarray results; a pathogenic CNV was detected in 230 (3.3%, 95% CI: 2.9%-3.8%) and a VUS in 483 (7.0%, 95% CI: 6.4%-7.6%). Of pregnancies with a pathogenic CNV, 20.0% (95% CI: 15.3%-25.6%) had a live birth, 3.0% (95% CI: 1.5%-6.2%) had a perinatal death (stillbirth or neonatal death), and 77% (95% CI: 71.1%-81.9%) had no birth record. Of those with a VUS, 64.4% (95% CI: 60.0%-68.5%) had a live birth, 1.8% (95% CI: 1.0%-3.5%) had a perinatal death, and no birth record was found for 33.7% (95% CI: 29.7%-38.1%). Most pathogenic CNVs (61.1%) were <7 Mb in size. The most common microdeletion syndromes were DiGeorge, Wolf-Hirschhorn, and Cri-du-chat syndromes. ConclusionThis study provides an overview of perinatal outcomes and frequency of recurrent CNVs observed in the prenatal microarray era.

Approximately 1 in 20 men are sub-fertile or infertile yet the aetiologies of male infertility remain largely unexplained. It is suggested that lifestyle choices and environmental factors contribute but research is limited. In particular, no study has evaluated early life exposures and subsequent male infertility. To address this knowledge gap, this study aims to characterise a cohort of men with idiopathic infertility and compare their general health, lifestyle choices and environmental exposures from teenage years onwards to men without reproductive abnormalities.Two groups of men (N = 500 cases; N = 500 controls), matched for age and socio-economic status, will be recruited from fertility clinics around Australia between June 2021 and June 2024. Men will be eligible if they are between 18 and 50 years, with a female partner less than 42 years, and have identified idiopathic male infertility (case) or are part of a couple with diagnosed female factor infertility but with no indication of compromised male fertility (control). Participants will complete an in-depth survey on general health, lifestyle and environmental exposures, reporting from teenage years onwards. An online medical data capture form will be used to gather fertility assessment information from participant medical records. Biological specimens of saliva (all study participants), blood and urine (optional) will be collected and stored for future genetic and epigenetic analysis. Differences in outcome measures between cases and controls will be determined using appropriate between groups comparisons. The relationship between explanatory variables and infertility will be analysed using multilevel modelling to account for clustering within fertility clinics.This study addresses an important gap in research on the aetiology of male infertility and will provide a comprehensive profile of the lifestyle and environmental risk factors for male infertility, leading to provision of up-to-date health advice for male teenagers and adults about optimising their fertility.Approximately 1 in 20 men are sub-fertile or infertile yet very little is known about the causes of male infertility. Research has suggested that lifestyle choices and environmental factors contribute to infertility, but more needs to be done to identify and verify the full suite of associations.We will recruit up to 1000 Australian male partners within couples who are seeking help from fertility clinics to get pregnant. They will be asked about their general health, lifestyle and environmental exposures at home or work over their lifespan. We will compare findings between men who are sub- or infertile with men who are not. Any differences will help us understand what factors may be associated with risk of infertility in men.This study will provide important information to clinicians and to inform public policy that will lead to prevention and improved treatment strategies for infertile men. The data gathered from this study will enable future research including the genetic and epigenetic basis of male infertility.

Background To analyze population-based trends in the prenatal diagnosis of sex chromosome aneuploidy (SCA) since the availability of non-invasive prenatal testing (NIPT). Methods Retrospective state-wide data for all prenatal diagnoses performed <25 weeks gestation from 2005 to 2020 in Victoria, Australia. Non-invasive prenatal testing became locally available from 2012. The prenatal diagnosis rates of SCA as proportions of all prenatal diagnostic tests and all births were calculated. Statistical significance was assessed with the chi(2) test for trend, with p 46,518 amniocentesis and chorionic villus sampling were performed during the study period, detecting 617 SCAs. There was a significant increase in the rate of prenatal SCAs from 5.8 per 10,000 births in 2005 to 8.7 per 10,000 births in 2020 (p < 0.0001). This increase was predominantly due to 47,XXY cases, 91% of which were ascertained via positive NIPT for this condition in 2020. The prenatal diagnosis rate of 47,XXY significantly increased from 0.8 per 10,000 births in 2005 to 4.3 per 10,000 births in 2020 (p < 0.0001). Conclusion Screening for SCAs using NIPT has directly led to an increase in their prenatal diagnosis on a population-wide basis, especially 47,XXY. This has implications for clinician education, genetic counselling, and pediatric services.

Numerous studies have investigated the physical health and development of children and adolescents conceived with assisted reproductive technology (ART). Less is known about the quality of life of ART-conceived adults. This study explores the contributions of being conceived with ART and psychosocial cofactors present in young adulthood to the quality of life of adults aged 22-35 years. Young adults conceived through ART or natural conception (NC) completed questionnaires which included a standardized measure of quality of life (World Health Organization Quality of Life - Brief assessment (WHOQoL-BREF)) when aged 18-28 years (T1) and again when aged 22-35 years (T2). The WHOQoL-BREF has four domains: (i) Physical, (ii) Psychological, (iii) Social relationships and (iv) Environment. A total of 193 ART-conceived and 86 NC individuals completed both questionnaires. When accounting for other cofactors in multivariable analyses, being ART-conceived was strongly associated with higher scores (better quality of life) on the Social relationships, and Environment WHOQoL-BREF domains at T2. In addition, less psychological distress, a better relationship with parents, a better financial situation, and perceptions of being about the right weight at T1 were associated with higher scores on one or more of the WHOQoL-BREF domains at T2. In conclusion, being ART-conceived can confer advantages in quality of life in adulthood, independent of psychosocial cofactors.

AIMS:To examine associations of assisted reproductive technology (ART) conception (vs. natural conception: NC) with offspring cardiometabolic health outcomes and whether these differ with age. METHODS AND RESULTS:Differences in systolic (SBP) and diastolic blood pressure (DBP), heart rate (HR), lipids, and hyperglycaemic/insulin resistance markers were examined using multiple linear regression models in 14 population-based birth cohorts in Europe, Australia, and Singapore, and results were combined using meta-analysis. Change in cardiometabolic outcomes from 2 to 26 years was examined using trajectory modelling of four cohorts with repeated measures. 35 938 (654 ART) offspring were included in the meta-analysis. Mean age ranged from 13 months to 27.4 years but was <10 years in 11/14 cohorts. Meta-analysis found no statistical difference (ART minus NC) in SBP (-0.53 mmHg; 95% CI:-1.59 to 0.53), DBP (-0.24 mmHg; -0.83 to 0.35), or HR (0.02 beat/min; -0.91 to 0.94). Total cholesterol (2.59%; 0.10-5.07), HDL cholesterol (4.16%; 2.52-5.81), LDL cholesterol (4.95%; 0.47-9.43) were statistically significantly higher in ART-conceived vs. NC offspring. No statistical difference was seen for triglycerides (TG), glucose, insulin, and glycated haemoglobin. Long-term follow-up of 17 244 (244 ART) births identified statistically significant associations between ART and lower predicted SBP/DBP in childhood, and subtle trajectories to higher SBP and TG in young adulthood; however, most differences were not statistically significant. CONCLUSION:These findings of small and statistically non-significant differences in offspring cardiometabolic outcomes should reassure people receiving ART. Longer-term follow-up is warranted to investigate changes over adulthood in the risks of hypertension, dyslipidaemia, and preclinical and clinical cardiovascular disease.

Objectives: To estimate the prevalence of vascular malformations using retrospective data collected from 1999 to 2020 in a specialty vascular anomalies service. Methods: The vascular anomalies service associated with the Royal Children’s Hospital provides a reference service to both adults and children, covering the entire state of Victoria, Australia, which has a population of 6.7 million and around 70,000 births per year. A database of patients was interrogated to identify those treated by the service over the study period with a diagnosis of vascular malformation, excluding capillary malformations. A total of 1501 patients were identified, including 1233 with slow-flow malformations and 147 with arteriovenous malformations. Prevalence was calculated as the number of cases born per year who attended the service plus those estimated as yet to attend for assessment, divided by the average number of live births each year. This was calculated for a selected period comprising the years when the numbers were expected to be most stable. Results: The prevalence of slow-flow malformations is estimated to be 1 case per thousand livebirths. Approximate estimates of cases per 100,000 births for individual lesions are: venous malformation 45, lymphatic malformation 35, intramuscular slow-flow malformation 10, complex malformations (Klippel-Trenaunay and CLOVES) 4, glomuvenous malformation 5, and verrucous venous malformation 2. The prevalence of extracranial arteriovenous malformation is estimated to be around one case per 10,000 population. Conclusions: An updated estimate, more accurate than those previously published, of the prevalence of vascular malformations has been obtained.