Women who are obese may stop breast-feeding babies sooner than other mothers, at least in part because they're uncomfortable nursing their babies when people are nearby, an Australian study suggests.

Researchers surveyed first-time mothers and found most of them intended to breast-feed before their babies were born, regardless of how much the women weighed. Most of the women expressed plans to nurse for about one year, and this didn't differ much based on whether they were obese.

But obese women were significantly more likely to anticipate discomfort nursing in front of even close female friends. And, the women who felt awkward or anxious being seen while breast-feeding stopped much sooner than women who didn't mind nursing in front of others.

"They seem to have all the same intentions, and have made the same decisions as smaller women, but confidence and comfort issues are a problem," said study co-author Dr. Ruth Newby of the University of Queensland in Brisbane.

Pediatricians recommend that mothers exclusively breast-feed infants until at least 6 months of age because it can reduce babies' risk of ear and respiratory infections, sudden infant death syndrome, allergies, childhood obesity and diabetes.

Mothers can benefit too, with longer periods of breast-feeding linked to lower risks of depression, bone deterioration and certain cancers.

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To see how obesity influences breast-feeding, Newby and her coauthor surveyed 462 women, giving them questionnaires once before the baby arrived and six times during the first year after birth. Each woman completed at least one of the questionnaires.

Among 258 women who provided a pre-pregnancy weight, they ranged from dangerously underweight to extremely obese, with an average size that put them right on the edge between a normal size and overweight.

Roughly one quarter of these women were overweight before pregnancy, and about 17 percent were obese.

Researchers had data on breast-feeding for 371 women, including 195 women who also provided information about their weight.

Among 347 women who had babies born at full-term, 98 percent nursed their infants at least once, researchers report in the European Journal of Clinical Nutrition.

Normal-weight women nursed significantly longer than overweight mothers, and obese women continued for much less time than even their overweight peers, the study found.

Though there wasn't a meaningful difference in the women's confidence about achieving their breast-feeding goals among the 274 participants who answered this question, obese women expressed much more discomfort about nursing in different social situations than other mothers.

The study doesn't prove obesity causes difficulties with breast-feeding, the authors caution.

Other limitations include the high proportion of women who didn't participate in each of the questionnaires as well as the reliance on mothers to accurately recall and report their weight and expectations and experiences with breast-feeding.

Even so, the findings suggest that more research is needed to understand the drivers of social discomfort with breast-feeding among obese women, the authors conclude.

Interventions during pregnancy might help address any body image issues or psychological barriers to breast-feeding and help increase the odds that obese women achieve their breast-feeding goals, the authors note.

Obese women may also need help overcoming physical obstacles that get in the way of successful breast-feeding, Newby said by email.

"Newborn babies have very tiny mouths, and larger women in particular may have quite large breasts," Newby said.

"If the baby's mouth milks the breast in an effective way, it empties the breast of milk and sets up hormonal signals which make more milk," Newby said. "It's supply and demand."

"Babies of larger mums don't always get a good grip or latch and may not be as good at emptying the breast and stimulating that milk supply for themselves," Newby added.