Each year an estimated 20 million children are born with low birth weight worldwide, more than 95% of them in developing countries.
Low birth weight, defined as less than 2,500 grams (5.5 pounds), is associated with increased risk of negative health outcomes, including neonatal and infant mortality, poor growth and cognitive development, and morbidity due to chronic diseases later in life, such as diabetes and heart disease. In a new study, the largest to date, researchers from the Harvard School of Public Health (HSPH) and Muhimbili University College of Health Sciences in Dar es Salaam, Tanzania, found that giving daily multivitamin supplements to HIV-negative women during pregnancy significantly reduced the risks of low birth weight and a small- for-gestational age birth size. There were no significant effects observed on the risks of prematurity or fetal death.
The study appears in the April 5, 2007 issue of the New England Journal of Medicine.
Birth weight is directly influenced by a number of factors, including maternal health, nutritional status and micronutrient deficiencies. Iron and folate supplements are routinely administered to pregnant women in many developing countries, including Tanzania, as part of standard prenatal care. However, many of these women are also deficient in a number of other micronutrients that are essential for maternal health and fetal and infant growth and survival. In a previous study by Fawzi and colleagues among HIV-positive pregnant women in Tanzania, multivitamin (B-complex, C and E) supplements significantly reduced the risks of adverse pregnancy outcomes, including pre-term birth, low birth weight and fetal death. As a result, multivitamin supplementation has been incorporated into a number of large-scale prenatal care programs for HIV-positive women. The current study was conducted to determine if the benefits of maternal multivitamin supplementation on birth outcomes applied to HIV-negative populations.
"In light of these findings, we recommend that multivitamins be considered for all pregnant women in developing countries, regardless of their HIV status," said Wafaie Fawzi, professor of nutrition and epidemiology at HSPH and principal investigator of the study.
The study involved 8,468 HIV-negative pregnant women. Participants were enrolled at 12 to 27 weeks gestation and randomly assigned to receive daily multivitamin or placebo supplements from enrollment until six weeks after delivery. The multivitamin supplements included vitamins B-complex, C and E; however, vitamin A and zinc were not included, based on findings from previous studies that failed to show a beneficial effect of these nutrients. All women also received iron and folate supplementation and malaria prophylaxis, as part of standard prenatal care in Tanzania.
The results demonstrated that multivitamin supplements significantly reduced the risks of low birth weight and a birth size that was small-for-gestational age by 18% and 23%, respectively. The researchers report that enhancing women's micronutrient status during pregnancy through daily supplementation has significant benefits on maternal immunity and hemoglobin levels, which would explain the protective effects on fetal growth.
The authors note that many developing countries already have a distribution system in place for provision of iron and folate supplements to pregnant women as part of standard of care. These supplements, produced in bulk by the United Nations Children's Fund (UNICEF), are available at a cost of less than one dollar for the duration of pregnancy. "Incorporating multivitamins into those supplements could be done without a large increase in cost and would be a highly cost-effective method of improving birth outcomes in developing countries," said Fawzi.