Women are more vulnerable to HIV infection when they are pregnant, with an infection rate more than double that among other women, a study from Uganda has found.

Dr. Ronald Gray of Johns Hopkins University compared HIV incidence between 3,134 pregnant women, 3,031 women who were breast-feeding and 30,545 other women over a ten-year study period between 1993 and 2003. This does not mean 36,710 women were studied; it means that 6,165 women out of the total moved into the categories of being either pregnant or breastfeeders at times during the course of the study.

It excluded from any one year a woman who said she had had no sex during that year; this left 24,258 women/years.

Pregnant women were tested when pregnancy was detected and again an average of four months after giving birth; other women were tested every 10-12 months.

The study found that the annual HIV incidence among pregnant women was 2.7 per cent, among breast feeders 1.4 per cent and women in neither category 1.1 per cent.

Gray went into detail to show that the doubling of HIV infection during pregnancy was unlikely to be due to other factors.

Factors likely to increase HIV infection in pregnant women were lower rates of condom use (five per cent versus nine per cent) and youth - 18 per cent of pregnant women were in the 15-19 age range compared with 10 per cent of the other women.

Factors likely to decrease HIV infection in pregnant women included them having fewer sex partners and being less likely to have genital ulcer disease. They were slightly less likely to have male sex partners who already had HIV (8.9 per cent versus 9.6 per cent) and the viral load amongst those male partners was slightly lower (13,000 vs 16,000, though this was not statistically significant).

On balance, Gray said, these factors should cancel each other out.

Rates of HIV infection among women with HIV positive regular partners was extremely high, and was again almost double that in other women; it was 15 per cent a year in pregnant women, 9.6 per cent in breastfeeding women and 8.3 per cent on the other women. Frequency of sex among pregnant women was no different from other women, and an analysis including the women who had not had sex the previous year came out with similar figures.

Having ruled out every external explanation for the doubling of HIV incidence in pregnant women, Gray said that further investigations were needed to elucidate what it is about pregnancy that increases susceptibility to infection. He suggested three possibilities; the thinning of the vaginal wall by high levels of progesterone; an increase in the number of CCR5 co-receptors in vaginal lymphocytes due to the same hormone (an effect already seen in contraceptive pills); and specific changes to the immune system induced by the presence of a foetus.

Reference

Gray R et al. Pregnancy and the risk of incident HIV in Rakai, Uganda, a cause for concern. Twelfth Conference on Retroviruses and Opportunistic Infections, Boston, abstract 19, 2005.

aidsmap resources

latest news

• HIV/TB epidemic in Eastern Europe a 'public health disaster'
• Low bone mineral density common in HIV-positive men
• Circumcision may protect HIV-negative gay men from syphilis
• HIV 'exposure' from bite forms basis for terrorism charge in US case
• First hint of a hepatitis C vaccine?
• Pregnancy, not nevirapine cause of liver toxicities in HIV-positive women
• Surviving to die of something else: AIDS is a rare cause of death in old people with HIV
• New EACS guidelines address co-morbidities and diseases of age
• Multiple pregnancies a safe option for women with HIV
• Small case series looks at etravirine during pregnancy