Prenatal vitamins may reduce the risk of low birth-weight babies for certain women, researchers say.

Low birth weight, or infants weighing less than 2,500 grams (about 5.5 pounds) at birth, is a major predictor of death during infancy and is also associated with an increased risk of heart disease, diabetes, stroke and high blood pressure later in life.

Low birth weight is especially a problem for women in countries low on resources and for low-income women, both of whom are often malnourished.

In a study published in the January issue of the Archives of Pediatrics & Adolescent Medicine, researchers from the University College of Medical Sciences in Delhi, India, and colleagues followed a group of 200 women who were 24 to 32 weeks pregnant and lived within 5 kilometers of a hospital in East Delhi, India.

The women either were underweight (with a body mass index less than 18.5) or had a low hemoglobin level (between 7 grams and 9 grams per deciliter), which can indicate malnourishment.

About half of the women were randomly assigned to take a daily prenatal vitamin containing a mix of 29 micronutrients. The other half were assigned to take a placebo pill. Both groups of women were given iron and folic acid supplements and guidance on prenatal health.

The researchers monitored the women during their regular prenatal clinic visits and collected information on their babies' birth weights and health status after the women gave birth.

The women taking the prenatal vitamins gained an average of 9.2 kilograms (20.3 pounds), compared with 8.7 kilograms (19.2 pounds) for the women taking the placebo.

The babies born to the women taking the prenatal vitamin also weighed an average of 98 grams (about 3.5 ounces) more than those born to the women taking the placebo. The rate of low birth weight in the vitamin group was 15.2 percent, compared with 43.1 percent in the placebo group.

Four infants died in each group.

In an editorial that accompanied the study, Rachel Haws and Gary Darmstadt, of the Bloomberg School of Public Health at Johns Hopkins University in Baltimore, wrote: "Neonatal deaths are traditionally viewed by child survival programs as relatively difficult to prevent, but new studies are strengthening the limited evidence base for highly cost-effective interventions that can save newborn lives in developing countries."