Now a new study offers important hope for at least one group of women who traditionally have met with lactation failure.
The research focused on overweight women, many of whom can have difficulty making enough milk for successful breast-feeding. Researchers say the study, presented May 3 at the Pediatric Academic Societies' annual meeting in Seattle, is the first to document a physical problem as a potential cause.
"The most important finding is that we have discovered a biological reason -- as opposed to a psychological or sociological reason -- for lactation failure," says study author Dr. Chris Kjolhede.
Kjolhede is a research scientist at Bassett Healthcare in New York state, who worked in conjunction with Cornell University scientists on the new finding.
The reason, Kjolhede believes, is related to decreased levels of prolactin, a hormone that originates in the pituitary gland in the brain, but is actually synthesized or utilized in many cells throughout the body.
During pregnancy, prolactin allows growth of the cells that help secrete milk. Shortly after birth, infant suckling at the breast stimulates a surge of prolactin, which, in turn, initiates rapid milk production in the breast.
If prolactin is in short supply -- either during pregnancy or shortly thereafter -- suckling appears to have a lessened effect on production of the hormone, Kjolhede says.
"We suspect that some overweight or obese women who intend to breast-feed actually fail to do so because of the blunted prolactin surge in response to suckling," Kjolhede says.
For obstetrician Dr. Steve Farber, the finding has merit, but he's less certain that being overweight is the only link to decreased prolactin.
"Prolactin is the hormone that makes milk, so lowered levels certainly can compromise milk production," says Farber. However, he adds the act of suckling is what causes prolactin levels to rise. "I'm not certain that being overweight would interfere with that -- at least not from what this study tells us thus far," Farber says.
He also points out that while some overweight women have problems breast-feeding, so do some normal weight women, or even women who are underweight. And, he says, no woman should be discouraged from breast-feeding if a lot of milk is not forthcoming right away.
"They can successfully supplement breast milk with formula and still give the child the benefits of breast-feeding," Farber says.
The new study involved 40 white women from rural New York state who had just given birth and planned to breast-feed. Beginning on the second day following delivery, each of the women received a blood test to measure prolactin levels just before a breast-feeding session, and again, 30 minutes after the attempt at infant suckling. The same tests were repeated again on day seven.
In the women diagnosed as overweight or obese before pregnancy, prolactin levels were significantly lower both on day two and day seven, says Kjolhede.
After taking into account both the baby's birth weight, whether this was the woman's first child, and the length of the actual suckling episode -- all of which can influence milk production -- the researchers conclude that being overweight remained a significant factor for difficulty breast-feeding.
"I think that what the results of our study show is that we need to identify women at risk for 'failure' and provide them with as much support as possible in the postpartum period," Kjolhede says.
To learn more about overcoming breast-feeding problems, visit La Leche League International. For more information on the benefits of breast-feeding, check A Woman's Guide To Breastfeeding from the American Academy of Pediatrics.