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Overweight Moms Have Trouble Nursing

Researchers find biological basis for lack of breast milk

MONDAY, May 3, 2004 (HealthDayNews) -- Overweight new mothers are more likely to quit breast-feeding early or not try it at all, and now researchers have found a reason why.

Women who are heavy have a diminished response to their baby's suckling, and this can adversely affect milk production, said Kathleen M. Rasmussen, a professor of nutrition at Cornell University and lead author of the study, which appears in the May issue of Pediatrics.

Immediately after birth, levels of the hormone progesterone fall, triggering the onset of milk secretion for breast-feeding. But for a continuing adequate milk supply, a baby's suckling must prompt an adequate increased concentration of prolactin, a hormone produced in the pituitary gland that stimulates the mammary glands to produce milk.

"The amount of prolactin the woman releases in response to the baby's suckling is what determines how much milk she makes between this feeding and the next," Rasmussen said.

In the study, Rasmussen and her co-author, Dr. Chris L. Kjolhede of Bassett Healthcare Research Institute in Cooperstown, N.Y., evaluated 40 mothers of infants, some normal weight and some not, measuring blood levels of prolactin and progesterone before and 30 minutes after the beginning of breast-feeding 48 hours after delivery and again at seven days after birth.

Overweight women had a lower prolactin response to suckling, they found. "In addition to other reasons [that many overweight women don't start and stay with breast-feeding], we have a strong biological explanation why," Rasmussen said. "They don't have an adequate prolactin response to suckling."

In theory, she added, that means less milk will be available, although the researchers did not directly measure the amount of milk the women produced.

Besides the biological explanation, Rasmussen said, heavier women may have a harder time positioning a baby for nursing, due to their size. It may be harder for the baby to "latch on" as well.

For the study, the researchers defined overweight as having a body mass index (BMI) of 26 before the pregnancy began. A woman 5 feet 5 inches tall who weighs 155 pounds has a BMI of 26. The normal-weight women in the study had an average BMI of 22 (a woman 5 feet 5 inches tall and 130 pounds), and the heavier women had an average BMI of 31.8 (nearly 190 pounds for a woman of the same height).

Exactly why the excess weight affects the prolactin response wasn't investigated, Rasmussen said.

The take-home point for women hoping to conceive and breast-feed successfully is clear, she added. "This is just another reason why women should conceive their babies at a healthy weight."

If that's not possible, the next best thing is to give an overweight new mother maximal support in her breast-feeding efforts, Rasmussen said. "We are talking about a substantial effort required," she said. In the study, the women's breast-feeding was assessed during every shift while they were in the hospital, and there were lactation consultants on call.

Another expert called the study "very interesting" and said help is available to these women. "These women can be helped to breast-feed even if their supply is lower," said Katy Lebbing, a registered lactation consultant and manager of the Center for Breast-feeding Information at LaLeche League International in Chicago.

The league maintains a specialty file, with names of leaders who are experts in specific areas. "One of our categories is large-breasted women," Lebbing said.

Another specialty area are babies who fail to thrive or gain weight slowly, which might be the case if a mother does not have enough milk.

Another option for overweight women who have trouble breast-feeding is to turn to human milk banks, Lebbing said. Women with excess milk donate to the banks. "Let's get these two groups of women together," Lebbing suggested.

The milk that is donated is screened for disease organisms and then heat-treated, she said. The professional association for human milk banking is the Human Milk Banking Association of North America.

More information

To learn more about breast-feeding, visit the La Leche League International. To learn more about human milk banking, try the Human Milk Banking Association of North America.

SOURCES: Kathleen M. Rasmussen, Sc.M., Sc.D., R.D., professor, nutrition, Cornell University, Ithaca, N.Y.; Katy Lebbing, registered lactation consultant and manager, Center for Breast-feeding Information, La Leche League International, Chicago; May 2004 Pediatrics
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