Reduced fertility associated with HIV: the contribution of pre-existing subfertility

Background: HIV-1 infection is associated with lower fertility among women in sub-Saharan Africa and this association is not explained by the frequenc y of sexual intercourse, illness, knowledge of HIV status or infection with other sexually transmitted diseases. Women with fertility problems are at increased risk of marital instability and, therefore, HIV infection; conseq uently, pre-existing subfertility among HIV-infected women may contribute t o the association. Objective: This study examines the relationship between HIV-1 infection and the incidence of recognised pregnancy and the role of low gravidity prior to seroconversion in rural Uganda. Methods: A group of 176 women (80 HIV infected and 96 uninfected) were enro lled into an HIV-1 natural history cohort and invited to attend 3-monthly c linic appointments. Data from clinic visits were analysed to assess the ind ependent effects of HIV infection and age, lactation, illness, reported fre quency of sexual intercourse and sexually transmitted diseases (STD) on the risk of pregnancy in the following 3 months. The number of previous pregna ncies was recorded at enrolment, and the effect of gravidity was examined f or the subgroup of women who were uninfected at enrolment or who enrolled w ithin 2 years of their estimated seroconversion date. Results: During follow-up, 124 pregnancies were observed in 83 women beginn ing in the 3 months following 47 (7.0%) of 669 visits made by HIV-infected women and 77 (9.5%) of 812 visits by HIV-negative women (P = 0.12). Adjusti ng for age, lactation, illness, STD and the reported frequency of sexual in tercourse, the estimated reduction in the risk of pregnancy associated with HIV infection was 47% [95% confidence interval (CI) 18-66]. Pre-existing l ow gravidity was strongly associated with a reduced incidence of pregnancy (odds ratio 0.39; CI 0.29-0.81). Additionally, adjusting for low gravidity reduced the estimate of the effect of HIV infection by almost a half, to 25 % (95% CI-57-29). Conclusion: Low gravidity prior to seroconversion accounts for almost 50% o f the observed association between HIV infection and lowered incidence of p regnancy, after adjusting for age, lactation, illness, STD and the frequenc y of sexual intercourse. (C) 1999 Lippincott Williams & Wilkins.