November 29, 2001
Breast-feeding among women infected with HIV type 1 is associated with substantial risk of HIV-1 transmission, yet little is known about the morbidity risk associated with formula feeding in infants of HIV-1-infected women in resource-poor settings. In resource-poor settings where the most prevalent causes of infant morbidity and mortality are infectious, there is the possibility that breast milk avoidance would be accompanied by an increase in mortality that might offset gains achieved by decreasing HIV-1 transmission.
The investigators conducted a randomized clinical trial between 1992 and 1998 of breast-feeding and formula feeding in Nairobi, Kenya. HIV-1-seropositive women were recruited from antenatal clinics in Nairobi and randomly assigned to breast-feed or to use formula to feed their infants. Mother/infant pairs were followed-up for 2 years after delivery. At each visit, information was obtained about feeding status, current and interim morbidity, and history of hospitalization. A physical examination was conducted, including measurement of weight and recumbent length. Ill children received outpatient care from study clinicians. Current morbidity was determined by study clinicians using standard diagnostic criteria. The incidence of infant illnesses in formula feeding and breast-feeding arms over the 2 years of follow-up and by quarter was compared using Andersen-Gill proportional hazards models, adjusting for number of clinic visits and with robust variance estimates.
Of 425 women enrolled in the study, 213 were randomly assigned to the formula feeding arm and 212 to the breast-feeding arm. Four hundred twenty infants were born to the 408 women who were in follow-up at the time of delivery. The results were similar for two-year estimated mortality rates in the formula feeding and breast-feeding arms (20.0 percent vs. 24.4 percent; hazard ratio [HR], 0.8; 95% confidence interval [CI], 0.5-1.3) even after adjusting for HIV-1 infection status. Infection with HIV-1 was associated with a 9.0-fold increased mortality risk (95% CI, 5.3-15.3). The incidence of diarrhea during the two-year follow-up was similar in both groups. The incidence of pneumonia was identical in the two groups and there were no significant differences in incidence of other recorded illnesses. Infants in the breast-feeding arm tended to have better nutritional status, significantly so during the first 6 months of life. HIV-1-free survival at two years was significantly higher in the formula arm.
In the conclusion of the study, the authors maintained that "With appropriate education and access to clean water, formula feeding can be a safe alternative to breast-feeding for infants of HIV-1-infected mothers in a resource-poor setting." However, the authors cautioned that the estimates of morbidity and mortality risk are not generalizable to all women in developing countries. They believe that the results of this study represent the best-case scenario because all participants had potable water, extensive health education, a reliable source of formula and access to medical care for their infants. It is also possible that the results may not be generalizable to uninfected women. It is possible that the breast milk of HIV-1-infected women lacks factors that confer protection from death, diarrheal disease, and pneumonia.