When the impact of breast-feeding on a child's long-term cognitive gains was still an open scientific question, the absence of knowledge was sort of a selling point.

"We could kind of say, 'Yeah, the research isn't there, but we think that could happen,'‚ÄČ" said Jill Branovsky, clinical director of maternity care at HealthEast's Woodwinds hospital in Woodbury. "Everybody wants their baby to be smart, right?"

But now an influential study in the journal Pediatrics has found little to no difference in IQ gains and behaviors between children who were breast-fed and those raised on formula bottles, and Branovsky said advocates can no longer make that inference. They must be true to science and give new and expecting mothers the facts about the pros and cons of breast-feeding their babies.

Midwives and lactation consultants across the Twin Cities have been discussing the new findings and whether they could undermine years of gains in mothers who at least attempt breast-feeding. At HealthEast, 89 percent of new mothers attempt breast-feeding, 76 percent stick with it for at least three months and 32 percent make it past six months.

Branovsky said she believes it will be a new and important part of the discussion with mothers, but that it won't change many decisions. That's partly because breast-feeding has other proven benefits, such as strengthening the immune system and reducing childhood obesity. And mothers also weigh practical factors such as the lower cost of breast-feeding compared to formula on one hand, and whether they will be able to pump breastmilk at work on the other.

The Pediatrics study tracked nearly 8,000 Irish children, using parent and teacher questionnaires to assess their skills in areas such as vocabulary and problem-solving at ages 3 and 5. No differences were observed among children breast-fed for less than six months, but researchers did find better problem-solving and less hyperactivity at age 3 in children who were breast-feed for six months or more.

However, the gain in problem-solving went away when researchers statistically controlled for factors such as parents' income and education levels. And the statistically valid reduction in hyperactivity at age 3 wasn't seen again at age 5.

Despite the findings, Branovsky said there is ample evidence that a nurturing bond between mother and child after birth is important to child development, and breast-feeding can still be one tool to promote that bond.

"We just can't just say it was breast-fed alone," she said.