Overweight moms have trouble nursing
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 wh 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."