Background Mother-to-child transmission is the predominant route of HIV-1 infection in children. Prevention strategies are available in industrialized countries, but are limited in developing countries. Defining pertinent characteristics of transmitted HIV-1 from mother-child pairs, where the actually transmitted virus has been traced, is important in creating better preventive measures against transmission of HIV-1.

ObjectivesThe aim of the study was to examine temporal and geographical patterns of mode of delivery in the European Collaborative Study (ECS), identify factors associated with elective caesarean section (CS) delivery in the highly active antiretroviral therapy (HAART) era and explore associations between mode of delivery and mother-to-child transmission (MTCT).MethodsThe ECS is a cohort study in which HIV-infected pregnant women are enrolled and their infants prospectively followed. Data on 5238 mother-child pairs (MCPs) enrolled in Western European ECS sites between 1985 and 2007 were analysed.ResultsThe elective CS rate increased from 16% in 1985-1993 to 67% in 1999-2001, declining to 51% by 2005-2007. In 2002-2004, 10% of infants were delivered vaginally, increasing to 34% by 2005-2007. During the HAART era, women in Belgium, the United Kingdom and the Netherlands were less likely to deliver by elective CS than those in Italy and Spain [adjusted odds ratio (AOR) 0.07; 95% confidence interval (CI) 0.04-0.12]. The MTCT rate in 2005-2007 was 1%. Among MCPs with maternal HIV RNA < 400 HIV-1 RNA copies/mL (n=960), elective CS was associated with 80% decreased MTCT risk (AOR 0.20; 95% CI 0.05-0.65) adjusting for HAART and prematurity. Two infants born to 559 women with viral loads < 50 copies/mL were infected, one of whom was delivered by elective CS (MTCT rate 0.4%; 95% CI 0.04-1.29).ConclusionsOur findings suggest that elective CS prevents MTCT even at low maternal viral loads, but the study was insufficiently powered to enable a conclusion to be drawn as to whether this applies for viral loads < 50 copies/mL. Diverging mode of delivery patterns in Europe reflect uncertainties regarding the risk-benefit balance of elective CS for women on successful HAART.

Objective: To assess pregnancy levels and patterns of HIV RNA in the absence of antiretroviral therapy, while appropriately adjusting for potential confounders, including maternal immune status and race.Methods: Data on >= 1 antenatal HIV RNA measurements were available for 333 untreated HIV-infected pregnant women enrolled in the European Collaborative Study. CD4 counts and HIV RNA measurements were routinely collected from 1992 and 1998, respectively. Linear mixed effects models based on 246 women for whom complete data were available examined changes in HIV RNA levels over pregnancy, with a nested random effects term accounting for measurement variability within women and period of sample collection.Results: The change in HIV RNA over pregnancy varied significantly by race (p = 0.005): from the second trimester until delivery, HIV RNA decreased significantly by an estimated 0.019 log(10) copies/ml/week in white women (95% Cl -0.03, -0.007); in black women the estimated 0.016 log(10) copies/ml/week increase (95% Cl -0.005, 0.037) was not statistically significant. At delivery, HIV RNA levels in black women were 0.45 log(10) copies/ml higher (95% Cl 0.08, 0.83) than in white women.Conclusions: Our findings suggest that HIV RNA dynamics over pregnancy differ by race, although other interpretations cannot be excluded, due to potential for unmeasured confounding. (C) 2008 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Objectives: To carry out an epidemiological analysis of the emerging epidemic in an Eastern European country and to compare the approach to prevention of mother-to-child transmission (MTCT) with that in Western Europe.Design: Prospective cohort study established in 1985 in Western Europe and extended to Ukraine in 2000.Methods: Data on 5967 HIV-infected pregnant women and their infants (1251 from Ukraine and 4716 from Western/Central Europe) was analysed. Factors associated with transmission were identified with logistic regression.Results: HIV-infection among pregnant women enrolled in Western European centres has shifted from being largely injecting drug use (IDU)-related to heterosexually-acquired; in Ukraine IDU also gradually declined with women increasingly identified without specific risk factors. In Ukraine in 2000-2004 most (80%) women received single dose nevirapine (sdNVP) and/or short-course zidovudine prophylaxis [MTCT rate 4.2%; 95% confidence interval (CI), 1.8-8.0 for sdNVP with short-course zidovudinel; 2% (n = 27) received antenatal HAART and 33% (n = 418) delivered by elective caesarean section (CS); in Western European centres 72% of women received HAART (MTCT rate 1.0%; 95% Cl, 0.4-1.9) and 66% delivered by elective CS during the same period.Conclusions: Our findings indicate distinct differences in the epidemics in pregnant women across Europe. The evolution of the MTCT epidemic in Ukraine does not appear to be following the same pattern as that in Western Europe in the 1980s and 1990s. Although uptake of preventive MTCT prophylaxis has been rapid in both Western Europe and Ukraine, substantial challenges remain in the more resource-constrained setting in Eastern Europe. (c) 2006 Lippincott Williams & Wilkins.

Objective To examine how the subsequent childbearing of HIV-infected mothers enrolled in the European Collaborative Study (ECS) has changed over time and identify factors predictive of further childbearing.Design Prospective cohort study.Setting Centres in nine European countries included in the ECS, enrolled between end 1986 and November 2003.Population HIV-infected women (3911): 3693 with only one and 218 with subsequent live births.Methods Univariable and multivariable logistic regression analyses to obtain odds ratios (OR) and 95% confidence intervals (CI). Kaplan-Meier (KM) analyses to estimate cumulative proportions of women having a subsequent live birth.Main outcome measures Subsequent live birth.Results In multivariable analysis adjusting for time period, ethnicity, maternal age and parity, black women were more likely [adjusted odds ratio (AOR) 2.45; 95% CI, 1.75-3.43], and women > 30 years less likely (AOR 0.54, 0.37-0.80), to have a subsequent live birth. Time to subsequent live birth significantly shortened over time, with an estimated 2% of women having a subsequent live birth within 24 months of enrolment pre-1989 versus 14% in 2000-2003 (P < 0.001). Estimated time to subsequent live birth was shorter for black than for white women (P < 0.001).Conclusions The likelihood of subsequent live births substantially increased after 1995 and birth intervals were shorter in women on HAART and among black women. Numbers are currently too small to address the issue of advantages and disadvantages in the management of subsequent deliveries.

Background. Risk factors for mother-to-child transmission of hepatitis C virus (HCV) are poorly quantified.Methods. We conducted a European multicenter prospective study of HCV-infected pregnant women and their infants. Children with >= 2 positive HCV RNA polymerase chain reaction test results and/or anti-HCV antibodies after 18 months of age were considered to be infected.Results. The overall HCV vertical transmission rate was 6.2% (95% confidence interval [CI], 5.0%-7.5%; 91/1479). Girls were twice as likely to be infected as boys (adjusted odds ratio [OR], 2.07 [95% CI, 1.23-3.48];). There was no protective effect of elective cesarean section (CS) delivery on HCV vertical transmission Pp. 006 (adjusted OR, 1.46 [95% CI, 0.86-2.48];). HCV/human immunodeficiency virus-coinfected women more Pp. 16 frequently transmitted HCV than did women with HCV infection only, although the difference was not statistically significant (adjusted OR, 1.82 [95% CI, 0.94-3.52];). Maternal history of injection drug use, prematurity, Pp. 08 and breast-feeding were not significantly associated with transmission. Transmission occurred more frequently from viremic women, but it also occurred from a few nonviremic women.Conclusions. Our results strongly suggest that women should neither be offered an elective CS nor be discouraged from breast-feeding on the basis of HCV infection alone. The sex association is an intriguing finding that probably reflects biological differences in susceptibility or response to infection.

Previously, we found that emergence of the X4 viral phenotype in HIV-1-infected children was related to the presence of X4 in their mothers (C. H. Casper et al., J Infect Dis 2002; 186: 914-921). Here, we investigated the origin of the X4 phenotype in the child, analyzing two mother-child pairs (Ma-Ca, Mb-Cb) where the mothers carried X4 and their children developed X4 after an initial presence of R5. We used nested polymerase chain reaction of the env V3 region to generate 203 HIV-1 clones for sequencing (Ma, n = 44; Ca, n = 73; Mb, n = 61; Cb, n = 25) from DNA of peripheral blood mononuclear cell (PBMC) lysates, altogether 167 clones, or from cDNA of plasma RNA, 36 clones. PBMC and plasma isolate sequences from each time point enabled us to assign the probable phenotype to clone sequences in a phylogenetic tree. The transmission and evolution were reconstructed using the maximum likelihood method. In mother-child pair Ma-Ca, one maternal R5 isolate clustered with the child's R5 sequences, at the earliest time when R5 was isolated in the child, confirming this as a likely source of the transmitted R5 phenotype. At age 3, an X4 population was present in the child that had evolved from the child's own R5-associated population, clearly distinct from the maternal X4 sequences. The second mother-child pair (Mb-Cb) displayed a similar pattern. Amino acid substitution patterns corroborated the conclusions from the phylogenetic tree. Thus, in both children, the X4 virus developed from their own R5 population, and was not caused by transmission of X4.

In Stockholm, Sweden, the majority of pregnant women positive for hepatitis B surface antigen (HBsAg) are hepatitis Be antigen (HBeAg) negative. Newborns to HBeAg positive mothers receive vaccination and hepatitis B immunoglobulin (HBIg). Newborns to HBeAg negative mothers receive vaccine and HBIg only if the mothers have elevated ALT levels. The aim of this study was to retrospectively evaluate ALT levels as a surrogate marker for HBV DNA levels in HBeAg negative carrier mothers. Altogether 8947 pregnant women were screened for HBV markers from 1999 to 2001 at the Virology Department, Karolinska Hospital. Among mothers screened 192 tested positive for HBsAg (2.2%). 13 of these samples could not be retrieved. Of the remaining 179 sera, 8 (4%) tested positive for HBeAg and 171 (95.5%) were HBeAg negative. Among the HBeAg negative mothers, 9 had HBV DNA levels > 10(5) copies/ml, and of these 7 had normal ALT levels indicating low sensitivity of an elevated ALT level as a surrogate marker for high HBV DNA level. Furthermore, no correlation was found between ALT and HBV DNA levels. Hence, it is concluded that the use of ALT as a surrogate marker for high viral replication in HBeAg negative mothers could be questioned.

Concerns have been raised over possible adverse effects of prophylactic antiretroviral therapy (ART) on the fetus and newborn. We analyzed data relating to uninfected children enrolled in the European Collaborative Study and investigated the association between ART exposure, perinatal problems, and major adverse health events later in life. Median length of follow-up was 2.2 (0-15.9) years. Of the 2414 uninfected children, 687 (28%) were exposed to ART in all three periods (antenatal, intrapartum, and neonatal). Of the 1008 infants exposed to ART at any time, 906 (90%) were exposed antenatally, 840 (83%) neonatally, and 750 (74%) both antenatally and neonatally. ART exposure was not significantly associated with pattern or prevalence of congenital abnormalities or low birth weight. In multivariate analysis, prematurity was associated with exposure to combination therapy without a protease inhibitor (PI) (OR = 2.66; 95% CI: 1.52-4.67) and with a PI (OR = 4.14; 95% CI: 2.36-7.23). ART exposure was associated with anemia in early life ( <.001). There was no evidence of an association with clinical manifestations suggestive of mitochondrial abnormalities. The absence of serious adverse events in this large cohort of uninfected children exposed to prophylactic ART in the short to medium term is reassuring.

Coreceptor use was determined for human immunodeficiency virus type 1 (HIV-1) isolates of various subtypes from 11 women during pregnancy and their infected children. Isolates from peripheral blood mononuclear cells (n=79) and from plasma (n=59) were available. The clinical and immunological stages of HIV-1 infection were recorded. Coreceptor use was tested on human cell lines expressing CD4 and different chemokine receptors. The R5 virus predominated, and only 9 isolates from 2 mothers used CXC chemokine receptor 4. All children carried the R5 virus at the time of diagnosis of HIV-1 infection. In 2 children of mothers carrying the X4 virus, the virus switched from R5 to X4 or to R5X4 by age 18 months (child no. 9) and age 48 months (child no. 10), whereas no children followed up to a similar age whose mothers were carrying the R5 virus experienced such a switch (P=.048). This points to a link between the presence of X4 virus in the mother and the emergence of X4 virus in her child.

Change of HIV-1 coreceptor use has been connected to progression of disease in children infected with HIV-1, presumably subtype B. It has not been possible to discern whether the appearance of new viral phenotypes precedes disease development or comes as a consequence of it. We studied the evolution of coreceptor use in HIV-1 isolates from 24 vertically infected children. Their clinical, virological, and immunological status was recorded and the env V3 subtype was determined by DNA sequencing. Coreceptor use was tested on human cell lines, expressing CD4 together with CCR5, CXCR4, and other chemokine receptors. The children carried five different env subtypes (nine A, five B, four C, three D, and one G) and one circulating recombinant form, CRF01_AE (n = 2). Of the 143 isolates, 86 originated from peripheral blood mononuclear cells (PBMCs) and 57 originated from plasma, received at 90 time points. In 52 of 54 paired plasma and PBMC isolates the coreceptor use was concordant. All 74 isolates obtained at 41 time points during the first year of life used CCR5. A change from use of CCR5 to use of CXCR4 occurred in four children infected with subtype A, D, or CRF01_AE after they had reached 1.5 to 5.8 years of age. There was a significant association with decreased CD4+ cell levels and severity of disease but, interestingly, the coreceptor change appeared months or even years after the beginning of the immunological deterioration. Thus CXCR4-using virus may emerge as a possible consequence of immune deficiency. The results provide new insights into AIDS development in children.

ObjectiveTo describe changes over a 15-year period in characteristics and management of HIV-infected pregnant women in Europe. DesignProspective study. MethodsAnalysis of prospective data on 2876 pregnant HIV-infected women and their 3076 infants. Factors examined included maternal socio-demographic, immunological and virological characteristics, antiretroviral therapy and pregnancy outcome. ResultsAmong women enrolled, the proportion with heterosexual acquisition of infection has increased significantly from 59% (201/342) in 1985–1987 to 69% (327/471) after 1997 while the proportion acquiring HIV through injecting drug use has declined. Overall median CD4 cell count was 440 × 106/l and 41% of women had undetectable viral load at delivery. In 1995 28% (72/256) of mother–child pairs received the full 076 regimen to reduce risk of vertical transmission, rising significantly to 89% (116/130) by 1999. Use of triple therapy started in pregnancy has increased significantly from < 1% (1/153) in 1997 to 44% (47/107) in 1999. Exposure to antiretroviral therapy was not associated with prevalence or pattern of congenital abnormalities (P = 0.88) but was associated with reversible anaemia in the infant (P < 0.002). The elective cesarean section rate has increased from 10% in 1992 to 71% in 1999/2000. The vertical transmission rate declined from 15.5% by 1994 to 2.6% after 1998. In multivariate analysis, adjusting for maternal CD4 cell count, risk of vertical transmission was reduced by 66% (95% confidence interval, 37–82%) with the full 076 regimen and by 60% (95% confidence interval, 33–73%) with elective cesarean section delivery. ConclusionsChanges in treatment of adult HIV disease have affected the management of infected pregnant women. Despite therapeutic and surgical interventions, vertical transmission still occurs.

Objective To investigate the effects of mode of delivery and infant feeding on the risk of mother-to-child transmission of hepatitis C virus.Design Pooled retrospective analysis of prospectively collected data.Sample Data on hepatitis C virus seropositive mothers and their children identified around delivery were sent from 24 centres of the European Paediatric Hepatitis C Virus Network.Main outcome measures Hepatitis C virus infection status of children born to hepatitis C virus infected women.Results A total of 1,474 hepatitis C virus infected women were identified, of whom 503 (35%) were co-infected with HIV. Go-infected women were more than twice as likely to transmit hepatitis C virus to their children than women with hepatitis C virus infection alone. Overall 9.2% (136/1474) of children were hepatitis C virus infected. Among the women with hepatitis C virus infection-only, multivariate analyses did not show a significant effect of mode of delivery and breastfeeding: caesarean section is vaginal delivery OR = 1.17: p = 0.661 breastfed versus non-breastfed OR = 1.07, P = 0.83. However, HIV co-infected women delivered by caesarean section were 60% less likely to have an infected child than those delivered vaginally (OR 0.36, p = 0.01) and those who breastfed were about four times more likely to infect their children than those who did not (OR = 6.41, P = 0.03). HIV infected children were three to four times more likely also to be hepatitis C virus infected than children without HIV infection (crude OR = 3.76, 95% CI 1.89-7.41).Conclusions These results do not support a recommendation of elective caesarean section or avoidance of breastfeeding for women with hepatitis C virus infection only, but the case for HIV infected women under,going caesarean section delivery and avoiding breastfeeding is strengthened if they are also hepatitis C virus infected.

Objective: To test the a priori hypothesis that longer duration of ruptured membranes is associated with increased risk of vertical transmission of HIV.Design: The relationship between duration of ruptured membranes and vertical transmission of HIV was evaluated in an individual patient data meta-analysis.Methods: Eligible studies were prospective cohort studies including at least 100 mother-child pairs, from regions where HIV-infected women are counselled not to breastfeed. Analyses were restricted to vaginal deliveries and non-elective Cesarean sections; elective Cesarean section deliveries (those performed before onset of labour and before rupture of membranes) were excluded.Results: The primary analysis included 4721 deliveries with duration of ruptured membranes less than or equal to 24 h. After adjusting for other factors known to be associated with vertical transmission using logistic regression analysis to assess the strength of the relationship, the risk of vertical HIV transmission increased approximately 2% with an increase of 1 h in the duration of ruptured membranes [adjusted odds ratio, 1.02; 95% confidence interval, 1.01-1.04; for each 1 h increment]. There were no significant interactions of duration of ruptured membranes with study cohort or with any of the covariates, except maternal AIDS. Among women diagnosed with AIDS, the estimated probability of transmission increased from 8% to 31% with duration of ruptured membranes of 2 h and 24 h respectively (P < 0.01).Conclusions: These results support the importance of duration of ruptured membranes as a risk factor for vertical transmission of HIV and suggest that a diagnosis of AIDS in the mother at the time of delivery may potentiate the effect of duration of ruptured membranes. (C) 2001 Lippincott Williams & Wilkins.

The relationship between time of HIV-1 detection, appearance of symptoms and disease progression was studied in all 24 HIV-1-infected infants from a cohort of 117 children who were born to HIV-1-infected mothers and monitored from birth. HIV isolation from plasma and mononuclear cells, HIV-1 DNA PCR (polymerase chain reaction) and, retrospectively, a quantitative assay for HIV-1 RNA were used for virus detection. Two infants possibly exhibited a symptomatic primary HIV infection. More children with than without symptoms during the first year of life progressed to immunological class 3 (P=0.013) and to AIDS or death (P=0.003) during follow-up. HIV-1 was detected within 4 days of age in 4 of 16 infants: 3 of them became symptomatic within 1 year, as did 6 of the remaining 12 infants (not statistically significant). All four infants in whom virus was detected within 4 days of age progressed to severe immunosuppression, compared to 6 of 14 in whom the virus detection test was initially negative prior to the first positive result (n.s.). Two children with previous repeatedly negative HIV detection tests were diagnosed with HIV-1 infection at 8 and 9 months, respectively. Repeated blood sampling is needed for the diagnosis of HIV-1 infection in perinatally exposed infants, and virus detection tests for exclusion of HIV-1 infection must be used with caution.

The presence of HIV in the placenta was analysed in relation to virological and immunological factors and vertical transmission of HIV in 39 pregnancies between 1989 and 1993 among 37 HIV-1-infected women without zidovudine prophylaxis. HIV-1 was detected in 12 of 37 (31%) placentas by immunohistochemistry and in 3 of 18 by PCR. Altogether 14/39 (36%) placentas bore evidence of HIV-1 infection, although there was no relation with the outcome of HIV infection in the child. Neither was there a relation between placental infection and either CD4 cell counts or HIV-1 RNA levels. However, HIV-1 was isolated from plasma in 20 of 39 (50%) pregnancies, which was inversely related to the presence of HIV in the placenta. When HIV-1 was identified in the placenta, HIV-1 was isolated from plasma in 3/14 (21%) pregnancies, vs 17/25 (68%) when it was not (p = 0.01), with a relative risk of having a placenta positive for HIV of 3.9 in pregnancies with a negative plasma HIV isolation. This inverse relation may point to differences in tropism between HIV-1 in placenta and plasma. The results show that the placental barrier prevents HIV transmission, irrespective of whether HIV enters the placenta or not.

ObjectiveTo assess the association between type and timing of initiation of antiretroviral therapy in pregnancy and duration of pregnancy. DesignProspective study. MethodsData on 3920 mother–child pairs were examined (3015 mother–child pairs from the European Collaborative Study and 905 from the Swiss Mother + Child HIV Cohort Study). Factors examined included gestational age, antiretroviral therapy during pregnancy, maternal CD4 count, viral load, illicit drug use (IDU) and mode of delivery. Deliveries at less than 37 weeks were defined as premature. ResultsThe prematurity rate was 17% and median gestational age 39 weeks. Twenty-three per cent (896 of 3920) of women received antiretroviral therapy during pregnancy: 64% (573 of 896) zidovudine monotherapy, 24% (215) combination therapy without protease inhibitors (PI) and 12% (108) combination therapy with PI. In multivariate analysis, adjusted for maternal CD4 count and IDU, odds ratio (OR) of prematurity was 2.60 [95% confidence interval (CI), 1.43–4.75] and 1.82 (95% CI, 1.13–2.92) for infants exposed to combination therapy with and without a PI, respectively, compared to no treatment. Exposure to monotherapy was not associated with prematurity, but severe immunosuppression and IDU in pregnancy were. Women on combination therapy from before pregnancy were twice as likely to deliver prematurely as those starting therapy in the third trimester (OR, 2.17; 95% CI, 1.03–4.58). ConclusionsPregnancy issues should be discussed when making decisions about initiation of combination antiretroviral therapy for HIV-infected women. Elective caesarean section to reduce vertical transmission at 36 weeks rather than 38 weeks may be advisable in women on combination therapy with PI.

Objective: Prophylactic zidovudine during pregnancy and labour reduces maternal viral load and, with neonatal therapy, has been shown to reduce vertical transmission. However, zidovudine may have additional effects. Advanced HIV disease is associated with premature delivery, which in turn results in increased vertical transmission. Data from the European Collaborative Study (ECS) were analysed to investigate whether zidovudine could be associated with decreased prematurity risk and/or with a reduced frequency of low birthweight.Methods: HIV-infected pregnant women enrolled in the ECS were followed prospectively according to a standard protocol. Gestational age was assessed by ultrasound, prematurity was defined as delivery before 37 weeks and the cut-off for low birthweight was 2500 g. We calculated odds ratios (OR) to estimate the effect of zidovudine on the risk of premature or low birthweight delivery.Results: In 2299 mothers, zidovudine taken to reduce the risk of vertical transmission decreased the odds of premature delivery by a quarter (OR = 0.76, 95% confidence interval (CI) 0.53-1.09), and the odds of low birthweight by nearly half (OR = 0.55, 95% CI 0.39-0.79). Allowing for CD4 count and mode of delivery did not greatly alter these OR values. A multivariate analysis suggested that prophylactic zidovudine and prematurity were independently associated with risk of transmission.Conclusion: Our findings suggest an additional health benefit of zidovudine. Even ii most vertical transmission occurs around the time of delivery, therapy earlier in pregnancy could have an indirect effect on transmission rates through delaying delivery. This hypothesis needs to be confirmed or refuted by more appropriate studies.

Background Results from observational studies suggest that caesarean-section delivery may reduce the risk of mother-to-child transmission of HIV-1 infection in comparison with vaginal delivery. We carried out a randomised clinical trial to address this issue and to assess the extent of postdelivery complications.Methods Eligible women were between 34 and 36 weeks of pregnancy, with a confirmed diagnosis of HIV-1 infection, and without an indication for caesarean-section delivery or a contraindication to this mode of delivery. Women were randomly assigned elective caesarean-section delivery at 38 weeks of pregnancy or vaginal delivery. An infant was classified as uninfected if he or she became negative for antibody to HIV-1 by age 18 months or was negative for virus by PCR or culture on at least two occasions, with no clinical, immunological, or viral evidence of infection. From 1993, to March, 1998, 436 women were randomised.Findings We present the results of an analysis updated to November, 1998, with data on the infection status of 370 infants. Three (1.8%) of 170 infants born to women assigned caesarean-section delivery were infected, compared with 21 (10.5%) of 200 born to women assigned vaginal delivery (p<0.001). Seven (3.4%) of 203 infants of women who actually gave birth by caesarean section were infected compared with 15 (10.2%) of 167 born vaginally (p=0.009). There were few postpartum complications and no serious adverse events in either group.Interpretation Our findings provide evidence that elective caesarean-section delivery significantly lowers the risk of mother-to-child transmission of HIV-1 infection without a significantly increased risk of complications for the mother.