Dr. Wendy Hazel Oddy of the Telethon Institute for Child Health Research in Perth and colleagues looked at 1,803 children and their mothers participating in a large pregnancy study. Eighteen percent of the women were overweight or obese before becoming pregnant.

After the researchers adjusted for factors including socioeconomic status and years of education, they found that women who were overweight or obese were less apt to attempt breastfeeding at all and those that did were less likely to continue breastfeeding.

Obese women were about twice as likely to have breastfed for less than two months or less than four months, while overweight women were 52 percent more likely than normal weight women to have stopped breastfeeding before two months, and 62 percent more likely to have stopped before four months.

Overall, the researchers found, overweight or obese women were 76 percent more likely to stop breastfeeding before their infants were six months old than their normal weight peers.

A number of factors could help explain the findings, the investigators say. For example, excess weight may change a woman's hormonal profile, making sustained lactation more difficult, or it may be harder for an infant to "latch on" to breast tissue if the mother is overweight or obese.

The researchers also report that overweight and obese women were more likely to have pregnancy complications and C-sections than normal-weight women.

SOURCE: The Journal of Pediatrics, August 2006.