Title: Pregnancy and acquisition of sexually transmitted infections
Description: This dissertation had three primary aims. The first aim was to systematically review evidence documenting incidence of sexually transmitted infections (STI) during pregnancy. Eighteen papers were included in the final review which reported incidence of five STIs: chlamydia, gonorrhea, human papillomavirus (HPV), herpes simplex virus type 2 (HSV-2) and human immunodeficiency virus (HIV). The review found that there are very limited data on incidence of STIs during pregnancy and even fewer data comparing risk between pregnant and non-pregnant women. Although data are limited, studies suggest that women continue to acquire STIs during pregnancy, with incidence varying by type of infection, population of interest and geographic setting. Highest incidence was found for HPV and chlamydia although some studies of chlamydia showed low proportions of pregnant women infected. Studies in which partners were known to be infected with HSV-2 and HIV showed higher rates of acquisition in pregnant women compared to studies where partner status was not known.

The second aim of this dissertation was to describe the impact of pregnancy on behavioral risk factors and vaginal practices that are associated with increased risk of STI acquisition. Data for this and the following aim came from the Methods for Improving Reproductive Health in Africa (MIRA) study, a randomized clinical trial conducted in South Africa and Zimbabwe 2003-2006. The analysis for the second aim included women in the MIRA trial who had a pregnancy during follow-up. Pregnancy was found to decrease sexual activity, particularly in the third trimester, but women were more likely to report sex without condoms while pregnant. There were lower reports by women during pregnancy of other risk factors for STI acquisition, including anal sex, concurrent sexual relationships and new sex partners. Vaginal wiping and insertion of material into the vagina, potentially important mechanisms for STI acquisition, were also less common during pregnancy. The data from this aim present a complicated picture of risk for STIs during pregnancy as a result of increased unprotected sex but decreased frequency of other known behavioral risk factors.

The third and final aim of the dissertation was to measure incidence of four STIs in pregnant and non-pregnant women and to evaluate whether women are at greater risk during pregnancy for acquiring four STIs: chlamydia, gonorrhea, trichomoniasis and HIV. This analysis included 4,549 women 18-50 years of age, 17% (N=766) of whom had a pregnancy during follow-up. In general, women continued to be sexually active but reported less overall sex than non-pregnant women. Report of condom use was lower during pregnancy as were other types of high risk sexual behaviors, such as multiple sexual partners, sex in exchange for drugs or money and anal sex, as well vaginal practices. STI incidence was measured during pregnancy and it was found that women continued to acquire STIs when pregnant. In addition, during periods when women became pregnant, they appeared to be a high risk for acquiring chlamydia, trichomoniasis and HIV. Finally, in examining the association between pregnancy status and STI risk, we found that in multivariable models adjusted for demographic and time-varying self-reported behavioral risk factors and vaginal practices, pregnancy was not associated with increased STI risk.

However in visit intervals when women became pregnant, they appeared to be at higher risk for contracting chlamydia compared to non-pregnant periods.