Lower incidence of pregnancy in HIV positive compared to HIV negative women in the Women’s Interagency HIV Study

Polly Clayden, HIV i-Base

Data are scant describing the relationship between HIV and conception.

The Women’s Interagency HIV Study (WIHS) is a multicentre US cohort of 3766 women with and without HIV. WIHS participants are broadly representative of HIV positive women in the US. They are mostly African American and half live below the poverty line.

An analysis published ahead of print in AIDS, looked at the incidence of pregnancy and time to conception among women in this cohort between 2002 and 2009.

Women were eligible if they were 45 years or below, sexually active with male partners, or reported a pregnancy outcome within the past year, and never reported hysterectomy, tubal ligation or oopherectomy.

Overall, 1412 women were at risk from becoming pregnant during this time period. Of these, 941 (67%) were HIV positive, and the remaining 471 (33%) were HIV negative. During follow up, 456 women reported 766 pregnancies; 404 (53%) were among the HIV positive women, and 362 (47%) the HIV negative women. Interestingly, 192 pregnancies occurred at the same visit that hormonal contraception was reported.

The investigators found an overall incidence of pregnancy in this group of 1.2 (95% CI 1.1-1.3) per 100 person years.

After adjusting for age, parity, alcohol consumption, exchanging sex, number of male sex partners and contraception use in the past six months, being HIV positive was associated with a 40% reduction in the rate of pregnancy, incidence rate ratio (IRR), 0.60 (95% CI 0.46-0.78). Also, it took 73% longer for HIV positive women to get pregnant compared to HIV negative women, relative time, 1.3 years (95% CI 1.35-2.36).

As would be expected, older age was also independently associated with a reduction in the incidence rate of pregnancy and the relative time to pregnancy was 30% longer in this group. Women with at least two sex partners in the past six moths had a 28% lower pregnancy rate and 64% lower time to pregnancy compared to those with only one (this was despite reporting lower baseline prevalence of contraception, 25 vs 75%, p<0.001). Women with at least three previous births conceived the fastest and had an incidence rate of pregnancy that was more than 12 times higher than those with no prior births.

Importantly, among the HIV positive women, women with a CD4 count of 350 cells/mm3 or more had a significantly faster time to first pregnancy than those with lower CD4 counts, p<0.0073.


Linas BS et al. Relative time to pregnancy among HIV-infected and uninfected women in the Women’s Interagency HIV Study, 2002-2009. AIDS. 2011 Mar 13; 25(5):707-711

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