Perinatal HIV-1 Transmission: Interaction Between Zidovudine Prophylaxis and Mode of Delivery in the French Perinatal Cohort

Context: It is unclear whether elective cesarean delivery may have a protective effect against the transmission of human immunodeficiency virus 1 (HIV-1).

Objective: To investigate whether mode of delivery has an impact on perinatal HIV-1 transmission in the presence of zidovudine prophylaxis.

Design: A prospective cohort study.

Setting: The 85 perinatal centers in the French Perinatal Cohort, from 1985 to 1996.

Patients: A total of 2834 singleton children born to mothers with HIV-1 infection.

Main Outcome Measure: Human immunodeficiency virus 1 infection of the infant.

Results: No zidovudine was used in 1917 pregnancies and zidovudine prophylaxis was used in 902 pregnancies. Cesarean deliveries were performed in 10.9% on an emergent basis and in 8.3% electively, prior to labor or membrane rupture. In 1917 mothers who did not receive zidovudine, of 1877 with information on mode of delivery, 17.2% transmitted HIV-1 to their child. Risk factors statistically significantly associated with transmission were maternal p24 antigenemia, cervicovaginal infections during pregnancy, amniotic fluid color, and rupture of membranes 4 hours or more before delivery. Mode of delivery was not related to transmission. In 902 mothers receiving zidovudine, transmission was 6.4% in 872 with information on mode of delivery, and elective cesarean delivery (n = 133) was associated with a lower transmission rate than emergent cesarean or vaginal delivery (0.8%, 11.4%, and 6.6%, respectively; P=.002). In a multivariate analysis of all mother-child pairs, including obstetrical risk factors, maternal p24 antigenemia, and zidovudine prophylaxis, interaction between mode of delivery and zidovudine prophylaxis was significant (P=.007). In the multivariate analysis of pregnancies with zidovudine prophylaxis, factors related to transmission rate were maternal p24 antigenemia, amniotic fluid color, and mode of delivery. Adjusted odds ratios (95% confidence intervals) were 1.6 (0.7-3.6) for emergent cesarean delivery and 0.2 (0.0-0.9) for elective cesarean delivery (P = .04) in comparison with vaginal delivery.

Conclusions: We observed an interaction between zidovudine prophylaxis and elective cesarean delivery in decreasing transmission of HIV-1 from mother to child. This observation may have clinical implications for prevention.