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 p rotective effect against the transmission of human immunodeficiency vi rus 1 (HIV-1). Objective.-To investigate whether mode of delivery has an impact on perinatal HIV-1 transmission in the presence of zidovudin e prophylaxis. Design.-A prospective cohort study. Setting.-The 85 per inatal centers in the French Perinatal Cohort, from 1985 to 1996. Pati ents.-A total of 2834 singleton children born to mothers with HIV-1 in fection. Main Outcome Measure.-Human immunodeficiency virus 1 infectio n of the infant. Results.-No zidovudine was used in 1917 pregnancies a nd zidovudine prophylaxis was used in 902 pregnancies. Cesarean delive ries were performed in 10.9% on an emergent basis and in 8.3% elective ly, prior to labor or membrane rupture. In 1917 mothers who did not re ceive zidovudine, of 1877 with information on mode of delivery, 17.2% transmitted HIV-1 to their child. Risk factors statistically significa ntly associated with transmission were maternal p24 antigenemia, cervi covaginal infections during pregnancy, amniotic fluid color, and ruptu re of membranes 4 hours or more before delivery. Mode of delivery was not related to transmission. in 902 mothers receiving zidovudine, tran smission was 6.4% in 872 with information on mode of delivery, and ele ctive cesarean delivery (n = 133) was associated with a lower transmis sion 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 antigen emia, and zidovudine prophylaxis, interaction between mode of delivery and zidovudine prophylaxis was significant (P=.007). In the multivari ate analysis of pregnancies with zidovudine prophylaxis, factors relat ed to transmission rate were maternal p24 antigenemia, amniotic fluid color, and mode of delivery. Adjusted odds ratios (95% confidence inte rvals) 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 vagina l 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 imp lications for prevention.