HIV incidence is high among pregnant and postpartum women and increases the risk of mother-to-child transmission

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HIV incidence is high among pregnant and postpartum women and is associated with an increased risk of mother-to-child transmission (MTCT) of HIV, results of a systematic review and meta-analysis published in PLOS Medicine show. The investigators stress the importance of offering repeat HIV tests to women in high-prevalence settings during pregnancy and breastfeeding.

Many women have an ongoing risk of acquiring HIV during pregnancy and breastfeeding. Therefore guidelines recommend that women who are identified as HIV negative during initial antenatal screening should have repeat HIV tests during pregnancy and postpartum. This rarely occurs, and to better inform prevention strategies, a team of US investigators performed a systematic review and meta-analysis of studies examining the incidence of HIV during pregnancy and postpartum and its association with vertical (mother to child) transmission of HIV.

Their review included studies published or presented to conferences between 1980 and the autumn of 2013. A total of 47 were included in their analysis.


mother-to-child transmission (MTCT)

Transmission of HIV from a mother to her unborn child in the womb or during birth, or to infants via breast milk. Also known as vertical transmission.

person years

In a study “100 person years of follow-up” could mean that information was collected on 100 people for one year, or on 50 people for two years each, or on ten people over ten years. In practice, each person’s duration of follow-up is likely to be different.


When the statistical data from all studies which relate to a particular research question and conform to a pre-determined selection criteria are pooled and analysed together.


The period of time from conception up to birth.

vertical transmission

Transmission of an infection from mother-to-baby, during pregnancy, childbirth, or breastfeeding.


Nineteen cohort studies – all involving people in sub-Saharan Africa – looked at incidence rates among pregnant and postpartum women. A total of 22,803 women were enrolled in the cohorts. The pooled results showed that HIV incidence was 3.8 per 100 person-years during pregnancy and 2.9 per 100 person-years postpartum.

Incidence of infection during pregnancy/postpartum was highest in southeast Africa (6.2 per 100 person-years), followed by south Africa (4.8 per 100 person-years), east Africa (2.7 per 100 person-years) and west Africa (0.7 per 100 person-years). Incidence was significantly higher in southeast Africa compared to west and east Africa.

“The pooled incidence rates we observed were comparable to, or higher than, those of non-pregnant ‘high risk’ individuals, including female sex workers…HIV-discordant couples…and men who have sex with men,” note the authors. “Both biological and behavioral changes have been hypothesized to explain the potentially higher risk of HIV acquisition observed during pregnancy and the postpartum period.”

Data on cumulative incidence rates during pregnancy/postpartum were provided in five studies, showing this was significantly higher in African compared to non-African settings (3.6 vs 0.3%; p < 0.001).

Rates of MTCT among women with incident infections during pregnancy/postpartum were reported in 13 studies. Vertical transmission rates ranged from 13% in the United States to 58% in Rwanda, with a pooled rate of 22.7%. Comparison between African and non-African settings showed a similar rate of vertical transmission (23.6 vs 22%, respectively). The pooled MTCT rate among women who acquired HIV during pregnancy was 17.8%, compared to 26.9% among women who acquired HIV postpartum, a non-significant difference.

Five studies compared the risk of MTCT among women with new infections during pregnancy/postpartum versus women with chronic HIV infection. Overall, infection with HIV during pregnancy/postpartum was associated with an almost threefold increase in the risk of MTCT (OR = 2.8; 95% CI, 0.9-4.7).

“HIV incidence among pregnant and postpartum populations was high in this meta-analysis and may substantially increase risk of MTCT,” conclude the investigators. “Our results have several implications for antenatal care/PMTCT programs.” First, all women in high-prevalence settings should be offered repeat HIV tests to detect incident infections during pregnancy/postpartum. Second, more sensitive testing assays should be used that detect both HIV antibodies and p24 antigen. Third, pregnant and postpartum women should receive counselling about the importance of ongoing condom use. The authors also believe that these women should be involved in the development of female-controlled methods of prevention, such as microbicides.


Drake AL et al. Incident HIV during pregnancy and postpartum and risk of mother-to-child HIV transmission: a systematic review and meta-analysis. PLOS Medicine, 11(2): e1001608, 2014.