Fig 1.
Profile of the evaluation of the effectiveness of the National Prevention of Mother-to-child transmission of HIV of the nested analysis of the maternal incident infection during pregnancy in South Africa, 2011–2012.
Table 1.
Socio-demographic characteristics of participating mothers and infants by maternal HIV status during pregnancy, South Africa, 2011–2012.
Fig 2.
Weighted relative proportion of maternal HIV seroconversions during pregnancy and early mother to child transmission of HIV (MTCT) by time of maternal HIV infection identified group, South Africa, 2011–2012.
This figure shows the distribution of awareness of HIV infection for all HIV-infected mothers, and for all mothers who transmitted HIV-infection to their infants. Mothers are categorized as a) knowing they were infected prior to this pregnancy (solid black) b) newly identified as HIV-infected during this pregnancy (upward diagonal lines) c) identified as HIV-infected by testing of infant dried blood spot specimens after reported not knowing their HIV status in our survey (solid grey box) and d) identified as HIV-infected by testing of iDBS after reporting testing HIV-negative in our survey, and with no other evidence of HIV infection reported on the infants child health card (light grey downward diagonal lines). Percentages are adjusted for the sampling design including clustering, design effects and nonresponse, and weighted to the population distribution of live-births for South Africa (SA) in 2011. It shows that, although women who seroconverted after a negative HIV test represent only 6.7% of the population of HIV-infected pregnant women in SA in 2011, these mothers accounted for 26.0% of all maternal to child transmission of HIV.
Table 2.
Weighted risk factors of the maternal HIV seroconversion during pregnancy, South Africa, 2011–2012 (Reduced multivariate model).
Fig 3.
Estimated time of seroconversion for mothers with a negative HIV test result during PMTCT but became infected during their current pregnancy, South Africa, 2011–2012.
This figure shows the results of a Kaplan-Meier (KM) time to event analysis of the time of seroconversion for 20 imputations of the weighted sample of 25,061 mothers represented by 211 sampled mothers who tested negative for HIV during this pregnancy and then became infected before they delivered their baby. Dashed lines represent the individual KM estimates for each of 20 imputations of the time of seroconversion, and the dark black line is the mean of these imputations. Median time of seroconversion was estimated to be 32.8 weeks of gestation, ranging from 31.5 to 33.6 across the imputations.
Fig 4.
Weighted risk of early mother to child transmission among mothers with HIV seroconversions during pregnancy compared to mothers with reported HIV-positive status prior to the current pregnancy.
This figure illustrates the estimate (diamonds) and 95% confidence intervals (vertical lines) for the proportion of HIV-infected mothers who had transmitted HIV to their infants by 4–8 weeks postpartum. Proportions are adjusted for the survey sampling design including clustering, design effects and nonresponse, and weighted to the population distribution of live-births for South Africa (SA) in 2011. The left panel of the graph shows a significantly higher proportion of mothers who seroconverted during pregnancy transmitted HIV to their infants than did mothers whose HIV infection was known to them before or during this pregnancy. The right panel subsets the women who seroconverted during pregnancy by the estimated week of gestation in which they seroconverted. Estimates of time of seroconversion were imputed using a uniform distribution to assign an equal probability of seroconversion to each day between delivery and the last reported negative HIV test during pregnancy. The graph shows results based on combined analysis of 20 imputations of this variable, and shows that the confidence intervals for the estimated proportion of mothers transmitting to their infants did not differ whether the mother was estimated to have seroconverted before or after 32 weeks gestation.