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Elective C-Section Reduces Vertical HIV Transmission


  • Does mode of delivery affect risk of vertical transmission of HIV?

Clinical Bottom Lines

  1. Elective c-section (before labor onset or rupture of membranes) reduces the risk of transmission of HIV from mom to baby as compared to non-elective c-section and vaginal delivery.1
  2. If zidovudine is used prenatally, intrapartum, and neonatally, and mom has an elective c-section, the risk of transmission to baby is further reduced.

Summary of Key Evidence

  1. In a meta-analysis of 15 prospective cohort studies from North America and Europe (about 8000 mother-child pairs), the risk of vertical transmission of HIV (without zidovudine prophylaxis) with elective c-section was 10.4 % and for non-elective c-sections and vaginal deliveries considered as a group, the risk was 19%.  This is a 8.6% absolute risk reduction, giving an NNT of 11.
  2. When AZT was used according to the standard of care (prenatal, intrapartum, and neonatal), the rate for elective c-sections was 2%, and for all other modes, it was 7.3%.  This produces an NNT of 18.

Additional Comments

  • Validity: 1) Studies not randomized 2) No description of validity checks 3) Results consistent.
  • Biological mechanism(s): possible explanations for decreased transmission in c-section are: contractions causing maternal-fetal transfusions; ascending infection after ROM; and exposure, via swallowing or thin mucous membranes, to maternal secretions and blood in birth canal.
  • Need to consider maternal risk of c-section, which is increased in HIV positive women, especially those with severe disease.
  • With use of triple therapy during pregnancy leading to very low viral loads, will c-section still be beneficial?


  1. The International Perinatal HIV Group.  Mode of delivery and the risk of vertical transmission of HIV-1.  New Engl J Med. 1999;340:977-987.
  2. Semprini AE, Castagna C, Ravizza M, et al.  The incidence of complications after c-section in 156 HIV-positive women.  AIDS 1995; 9:913-917.
  3. Shaffer N, Roongpisuthipong A, Siriwasin W, et al.  Maternal viral load and perinatal HIV-1 subtype E transmission, Thailand.  J Infect Dis 1999; 179:590-599.
  4. Kuhn L, Steketee RW, Weedon J, et al.  Distinct risk factors for intrauterine and intrapartum HIV transmission and consequences for disease progression in infected children.  J Infect Dis 1999: 179:52-58.
  5. Cosmas Van De Van, M.D., personal communication.

CAT Author: Rachel Frank, MD

CAT Appraisers: John Frohna, MD

Date appraised: April 12, 1999

Last updated February 16, 2003
Department of Pediatrics and Communicable Diseases
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