Impact of Maternal HIV Seroconversion during Pregnancy on Early Mother to Child Transmission of HIV (MTCT) Measured at 4-8 Weeks Postpartum in South Africa 2011-2012: A National Population-Based Evaluation.
BACKGROUND
Mother-to-child transmission of HIV (MTCT) depends on the timing of HIV infection. We estimated HIV-seroconversion during pregnancy (HSP) after having a HIV-negative result antenatally, and its contribution to early MTCT in South Africa (SA).


RESULTS
Between August 2011 and March 2012, we recruited a nationally representative sample of mother-infant pairs with infants aged 4-to-8 weeks from 578 health facilities. Data collection included mother interviews, child health-card reviews, and infant dried-blood-spots sample (iDBS). iDBS were tested for HIV antibodies and HIV-deoxyribonucleic-acid (HIV-DNA). HSP was defined as maternal self-report of an HIV-negative test during this pregnancy, no documented use of antiretroviral drugs and a matched HIV sero-positive iDBS. We used 20 imputations from a uniform distribution for time from reported antenatal HIV-negative result to delivery to estimate time of HSP. Early MTCT was defined based on detection of HIV-DNA in iDBS. Estimates were adjusted for clustering, nonresponse, and weighted by SA's 2011 live-births.


RESULTS
Of 9802 mother-infant pairs, 2738 iDBS were HIV sero-positive, including 212 HSP, resulting in a nationally weighted estimate of 3.3% HSP (95% Confidence Interval: 2.8%-3.8%). Median time of HIV-seroconversion was 32.8weeks gestation;28.3% (19.7%- 36.9%) estimated to be >36 weeks. Early MTCT was 10.7% for HSP (6.2%-16.8%) vs. 2.2% (1.7%-2.8%) for mothers with known HIV-positive status. Although they represent 2.2% of all mothers and 6.7% of HIV-infected mothers, HSP accounted for 26% of early MTCT. Multivariable analysis indicated the highest risk for HSP was among women who knew the baby's father was HIV-infected (adjusted-hazard ratio (aHR) 4.71; 1.49-14.99), or who had been screened for tuberculosis (aHR 1.82; 1.43-2.32).


CONCLUSIONS
HSP risk is high and contributes significantly to early MTCT. Identification of HSP by repeat-testing at 32 weeks gestation, during labor, 6 weeks postpartum, in tuberculosis-exposed women, and in discordant couples might reduce MTCT.
Centers for Disease Control and Prevention, Center for Global Health, Division of Global HIV/AIDS, Atlanta, Georgia, United States of America.
Thu-Ha
TH
Dinh
Centers for Disease Control and Prevention, National Center for HIV, Hepatitis, STD, and Tuberculosis Prevention, Division of HIV/AIDS Prevention, Atlanta, Georgia, United States of America.
Kevin P
KP
Delaney
Medical Research Council, Pretoria, South Africa; Department of Paediatrics and Child Health, Kalafong Hospital, University of Pretoria, Pretoria, South Africa.
Ameena
A
Goga
Medical Research Council, Cape Town, South Africa; United Nations Children's Fund, New York, United States of America.
Debra
D
Jackson
School of Public Health, University of the Western Cape, Bellville, South Africa.
Carl
C
Lombard
School of Public Health, University of the Western Cape, Bellville, South Africa.
Selamawit
S
Woldesenbet
US Centers for Disease Control and Prevention, Center for Global Health, Division of Global HIV/AIDS, Pretoria, South Africa.
Mary
M
Mogashoa
National Department of Health, Pretoria, South Africa.
Yogan
Y
Pillay
World Health Organization, Geneva, Switzerland.
Nathan
N
Shaffer
D000328:Adult; D000914:Antibodies, Viral / Q000097:blood; D005260:Female; D015658:HIV Infections / Q000175:diagnosis* / Q000517:prevention & control / Q000635:transmission*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D018445:Infectious Disease Transmission, Vertical / Q000517:prevention & control*; D007774:Lactation; D049590:Postpartum Period; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis*; D000069078:Seroconversion; D013019:South Africa
D000914:Antibodies, Viral