Breastfeeding may increase maternal mortality among HIV-positive women, study shows

A randomised study of HIV-positive Kenyan women with infants, appearing in the current issue of the Lancet, found that breastfeeding may raise the risk of maternal and infant death, even after controlling for infant death from HIV infection.

Researchers from the University of Nairobi and the University of Washington from November 1992 to October 1997 recruited 425 HIV-positive pregnant women from four Nairobi city council clinics and, at 32 weeks gestation, randomly divided them into two groups, directing 212 to breastfeed and 213 to formula feed their infants. The women were counselled “with respect to optimum feeding practices” and followed up every month for the first year after delivery and then quarterly during the second year, until death or the end of the study. Hospital records or reports from relatives were used to determine cause of death for those who passed away during the study. The study was monitored by a data and safety board.

Results

Of the women in the breastfeeding group, eight were lost to follow-up before delivery, one died during pregnancy and six had “no vital status information” post-delivery, leaving a total of 197 in the mortality analysis. Thirty-nine of those women were lost to follow-up, and 18 died during the follow-up period. Of the women using formula, 33 were lost to follow-up, and six died during the follow-up period. The relative risk of death for breastfeeding mothers versus formula-feeding mothers was 3.2, and the “attributable risk” of maternal death due to breastfeeding was 69%. The difference in mortality rates was “significant” as early as six months post-delivery. Infants of HIV-positive women who died also showed an eight-fold increase in the likelihood of death, even after controlling for HIV infection status.

Reasons for the increased mortality rate

The researchers speculated that the “combined metabolic burdens” of HIV and breastfeeding among women with “substantial nutritional impairment” may cause an increased amount of weight loss and maternal depletion syndrome, in which women do not replenish the vital nutrients lost during pregnancy and breastfeeding. The researchers also said that the lactation-related rise in the immunomodulating hormone prolactin may cause immunosuppression, leaving the women more vulnerable to AIDS-related infections. These findings “warran[t] assessment,” the authors state. “Our aim should be to ensure that all HIV-1 infected mothers are able to feed their infants in a way that keeps risk to a minimum for both mother and child,” they conclude (Nduati et al., Lancet, 26/05).

More research needed

In an accompanying op-ed, Marie-Louise Newell of the Institute of Child Health in London, writes that further research on the link between breastfeeding and maternal mortality is necessary because the new findings are “not in keeping” with the results of a study conducted in Durban, South Africa. That study found “no evidence of an association between clinical problems in the mother and duration of breastfeeding,” she states. In that study, two of the 410 women who exclusively breastfed died, while three of the 156 women who used formula died. Newell also points out that in the Kenyan group, the rate of intrauterine HIV transmission was higher among the breastfeeding group, which may indicate that they were already in a “more advanced” stage of the disease than the women in the other group (Newell, Lancet, 26/05).

WHO breastfeeding recommendations

The study results come on the heels of a World Health Assembly resolution on breast milk substitutes adopted at the World Health Organization body’s recent meeting in Geneva. The resolution calls on member nations to “protect, promote and support exclusive breastfeeding for six months as a global public health recommendation, and to provide safe and appropriate complementary foods, with continued breastfeeding, for up to two years of age or beyond.” The resolution also called for continued “independent research” on the risk of HIV transmission through breastfeeding (WHA release, 22/05).