Vertical transmission of HIV-1: Maternal immune status and obstetric factors

Objective: To estimate the effect of maternal factors and events around the time of delivery on HIV-1 vertical transmission risk. Design: Prospective study. Setting: Twenty-two obstetric and paediatric clinics in seven European countries. Patients or other participants: Mothers identified as HIV-infected before or at delivery and their children. Main outcome measure: Paediatric HIV infection. Results: By November 1995, 1846 mothers with 1945 children had been enrolled. The vertical transmission rate was 16.4% (95% confidence interval, 14.5-18.3). Parity, maternal age, race, mode of HIV acquisition, injecting drug use and sex of infant were not statistically significantly associated with risk of transmission, Children delivered vaginally were more likely to be infected than those delivered by Caesarean section. However, in vaginal deliveries the procedures used, duration of ruptured membranes or length of second-stage labour were not related to transmission. Transmission increased almost linearly with decreasing CD4 cell count, but there was no such trend for CD8 cell count. Women with CD4 cell counts below 200 x 10(6)/l were significantly more likely to deliver early (chi(2) for trend, 14.02; P < 0.001). Very premature infants were at increased risk of infection, but after about 35 weeks gestation the transmission rate remained stable, with no increase in late pregnancy. This trend was confirmed after allowing for maternal CD4 cell count. Conclusions: The rate of vertical transmission increases linearly with decreasing maternal CD4 cell count. Women with fewer than 200 x 10(6) CD4 cells/l have an increased risk of premature delivery, which would affect timing of interventions. The stable transmission rate after 35 weeks gestation suggests little acquisition of infection during late pregnancy

Cesarean-section and Risk of Vertical Transmission of Hiv-1 Infection

Indirect evidence suggests that a significant proportion of vertical transmission of HIV infection occurs late in pregnancy or during delivery. Caesarean section, therefore, may protect the fetus from infection. We looked at 1254 HIV-infected mothers and their children and the effects of different modes of delivery on transmission risk. We also included a detailed assessment of confounding factors associated with transmission risk. Women who had caesarean sections were more advanced in their disease progression which may cause the protective effect of caesarean section to be underestimated. When this and other potential confounding factors were taken into account, caesarean section was estimated to halve the rate of transmission. This finding is important in the design of studies to evaluate treatments aimed at reducing mother-to-child transmission

Perinatal Findings In Children Born To Hiv-infected Mothers

Objective To explore in children born to HIV-infected women, the association between a child's HIV infection status and birthweight, gestational age, congenital abnormalities and other perinatal findings. Design A prospective study of children born to women known to be HIV-infected at or before the time of delivery enrolled in the European Collaborative Study. Setting Nineteen European centres. Subjects A cohort of 853 children with known HIV infection status. Results There was no evidence for an HIV dysmorphic syndrome, and the frequency of congenital abnormalities was similar in infected and uninfected children with no consistent pattern of defects. Injecting drug use during pregnancy had the most marked effect on birthweight and gestational age. Multivariate analysis demonstrated a weak association between birthweight and the child's HIV infection status, but this could partly be explained by the confounding effect of maternal immunological HIV status. HIV infection in the infant was not associated with gestational age, and the mean and distribution of gestational age were similar for infected and noninfected children. Conclusions The finding that HIV-infected and noninfected children are of similar birthweight, the absence of a dysmorphic syndrome and no evidence of associated congenital abnormalities suggest that a substantial proportion of infection occurs late in pregnancy or at the time of delivery

Immunological markers in HIV-infected pregnant women

Objective: To examine immunological markers in HIV-infected pregnant women. Design: Women enrolled in the European Collaborative Study and the Swiss HIV Pregnancy Cohort were followed throughout pregnancy according to similar clinical and immunological protocols. Information was recorded at various times during pregnancy and, in some centres, also 6 weeks and 6 months post-partum. Method: Locally-weighted linear regression analysis was used to investigate changes in markers of cellular and humoral immune function during pregnancy and immediately post-partum, taking into account the serial measurement data structure. Women who received zidovudine during pregnancy were excluded. Results: Four hundred and thirty-eight women had two or more measurements during pregnancy or within 6 months of delivery. Twenty-four per cent (106) of the women reported injecting drugs during pregnancy. Mean CD4 and CD8 cell counts declined to a low level 6 months before delivery, increased gradually until delivery and rose sharply to a peak level 3 months post-partum. In contrast, CD4 and CD8 percentages were stable during pregnancy, and increased slightly thereafter. The same pattern was evident for transmitting women, those delivered by Cesarean section, and women who injected drugs during pregnancy, and there was no evidence for an association with immunosuppression. Total immunoglobulin (Ig) G levels declined gradually throughout pregnancy until delivery, and increased in the 6 month post-partum period. Total IgM and IgA levels remained stable throughout pregnancy. Conclusions: These findings suggest that pregnancy does not accelerate HIV progression, but in view of the intrinsic variability in serial CD4 counts, caution should be exercised when assessing changes in immunological markers in individual pregnant women