Effect of HIV infection on pregnancy

HIV infection has been reported to have little effect on pregnancy outcome or complications in the developed world^77,82,83,84. It is often difficult to determine the relative contribution of HIV infection, drug use and inadequate antenatal care to adverse outcomes in these women^85,86. Adverse pregnancy outcomes have, however, been reported more commonly in a number of African studies^{87,88,89,90,91} including complications of both early and late pregnancy. HIV may be the direct cause or a marker of a complex interaction of related medical and social conditions that affect pregnancy. Other studies have demonstrated no association⁸⁴. These complication rates vary across studies and may reflect the extent of the epidemic and the nature of HIV-related diseases in different communities.

Complications of early pregnancy have been associated with HIV infection in several studies^{75,77,79,92,93}. HIV-1 and HIV-2 infection in Africa have both been linked to a higher rate of spontaneous abortion⁸. HIV seropositive women were 1.47 times more likely to have had a previous spontaneous abortion, and this rose to 1.81 in women in Uganda who were seropositive for both HIV and syphilis⁹⁴. An American study showed a three-fold increase in early spontaneous abortion in a prospective follow-up study^92,95. More than half of these aborted fetuses had evidence of HIV infection, particularly with the thymus gland affected.

Higher rates of ectopic pregnancy have been reported in HIV-positive women than in uninfected women, which may be related to the effects of other concurrent sexually transmitted infections. Genital tract infections such as Neisseria gonorrhoea, Chlamydia trachomatis, Candida albicans and Trichomonas vaginalis infection have been reported to be more common in women with HIV^96,97. Syphilis is more common in HIV-positive women in African studies. Concurrent infection with syphilis was shown in 33% of HIV-positive pregnant women in South Africa: three times higher than the rate in HIV seronegative women⁹⁶. These high rates of syphilis may confound studies of pregnancy outcome unless the potential bias is taken into account in analysis. All HIV-positive pregnant women should be screened for syphilis, even in low prevalence areas⁹⁷.

Bacterial pneumonia, urinary tract infections and other infections are more common during pregnancy in HIV seropositive women^91,98,99. In addition to these infections and parasitic infestations, any of the HIV-related opportunistic infections can be found during pregnancy. Tuberculosis is the commonest opportunistic infection associated with HIV in the developing world, and particular attention should be paid to its diagnosis in pregnant HIV-positive women. Herpes zoster is common in young HIV-positive women, although uncommon in this age group in the absence of HIV infection¹⁰⁰. Kaposi's sarcoma has been reported during pregnancy in HIV-positive women¹⁰¹.

Preterm labour may be more common in HIV-positive women, with rates as high as double those rates seen in uninfected women in some reports^79,90,102. Preterm rupture of membranes may also be increased in HIV-positive women and abruptio placentae has been described as more common in HIV-positive women in Kenya and South Africa ^{88, 103}.

There is little difference in the birth weight of babies born to HIV-positive mothers in developed countries^104,105. In Edinburgh, HIV seropositivity was associated with a decrease in birth weight, but this was less than the drop attributable to smoking¹⁰⁶. Low birth weight has been reported in some studies in developing countries^100,107. In a Nairobi study, HIV-positive women showed a threefold increase in the risk of delivering a low birth weight baby¹⁰³. This risk was higher with symptomatic HIV infection. In Zambia, the birth weights of babies born to HIV-positive mothers were significantly lower than those of babies of seronegative women. In a prospective study in Rwanda, birth weight was significantly lower in singleton infants of asymptomatic women, although the difference in mean birth weight between the two groups was only 120 g¹⁰⁷. Other studies in predominantly asymptomatic cohorts have shown no significant difference in birth weights¹⁰⁸.

Increased stillbirth rates have been reported, especially from areas where the epidemic has been present for a long time. The risk appears to be lower in asymptomatic women, although stillbirth rates more than double those in HIV sero-negative mothers have been shown in some African centres. However, some of the reported studies do not control for the presence of syphilis or other factors associated with stillbirth. A large study in Nairobi showed an independent association between HIV infection and both intra-uterine and intra-partum death, after controlling for the presence of other STIs⁹⁰.

Infectious complications are also more common during the postpartum period in HIV-positive women^88,102,109. Caesarean section is particularly associated with higher infectious morbidity in some reports, especially in women with low CD4+ counts, with an increased mortality in one Rwandan study^109,110.