Sept. 25, 2009 -- Throughout her pregnancy, Michele Walker-Lewis researched data on vaccines, breast feeding and circumcisions, and even interviewed seven potential pediatricians to find one she could trust.
"You have to collaborate with your doctor, but be informed," said Walker-Lewis of the ever-changing field of medicine and child rearing where advice changes on a dime.
But now the New Jersey mother-to-be, who is "ready to go" and expecting a boy in October, has one more thing to worry about -- whether her son will have a flat head.
New research confirms what doctors have seen in a generation of babies -- that 1 in 40 babies who sleep on their backs will develop a flat head, making them more prone to ear infections and long-term complications such as language disorders and learning disabilities.
The study, published in the September issue of The Journal of Craniofacial Surgery, warns about a 49 to 54 percent increase in ear infections in a skull deformity known as deformational or positional plagiocephaly.
"It's been around since the mid-'90s and it's pretty common these days," said Dr. Lisa David, senior researcher on the Wake Forest University Medical Center study.
"It's just one more thing to research and discuss the risks and benefits," said Walker-Lewis, who works in the fashion business. "Circumstances change and risk factors change."
Each year in the United States, more than 4,500 infants die suddenly of no obvious cause. About half of them are attributable to Sudden Infant Death Syndrome (SIDS), the leading cause of death among infants 1-12 months old, according to the Centers for Disease Control and Prevention.
Doctors still don't know what causes SIDS, but suspect that it may have something to do with abnormalities in the part of the brain that control breathing and waking during sleep, according to First Candle/SIDS Alliance, a health organization committed to infant survival.
These flaws could stem from exposure to toxins or lack of oxygen in the prenatal stage, they say.
Stomach Sleeping in Babies Under Four Months Risky for SIDS
It is also thought that sleeping on the stomach, with the baby's airway so close to the mattress, could affect oxygen intake by rebreathing. Pediatricians say some babies just "forget" to breathe.
The so-called Back to Sleep campaign -- warning parents about the dangers of babies sleeping on their stomachs -- was launched in 1994 with an effort to reach every newborn in the nation.
Since then, doctors have seen more cases of flat head, the result of pressure on the skull from lying in the same position. Treatment consists of a helmet or band to gently mold the growing skull back into shape.
Earlier detection is key -- before four months of age. After that, sleep patterns have been established and flat heads are "self-perpetuating," and treatment is longer, according to David, a craniofacial surgeon.
"Imagine wearing a bun or a pony tail," she said. "When an area of their skull sticks out, they gravitate toward the flat side. The more comfortable it is, the flatter it gets."
Across the board, doctors stress that back sleeping has saved so many babies that parenting advice is not likely to change.
For children who are premature, have reflux, live among smokers or are under four months old, "yes, it's risky on the stomach," said David. "It's less risky after six months, when babies are flipping themselves."
This flat head phenomenon comes as a surprise to many mothers.
"I don't remember the pediatrician telling me about it," said Stephanie Goldman, a special events manager for the New York office of the South African Ubuntu Education Fund. "The baby nurse told me, otherwise I wouldn't have known."
While back sleeping has cut SIDS deaths, it confounds mothers who say babies prefer their tummies.
Goldman swaddled her newborn in a Velcro wrap to help her adjust to her back.
"I'd put her to sleep like a little egg roll," Goldman told ABCNews.com. "Some people do it for a year."
She also has heeded advice to prevent flat head by repositioning her daughter with bolsters under crib sheets. Goldman and other mothers plan "tummy time" during the day to help strengthen neck muscles that tummy sleepers use in bed.
Pediatricians also recommend time spent outside the crib in car seats, carriers and activity gyms and that draw their heads to a new position. Pacifiers at bedtime, long demonized by doctors, are now recommended to prevent SIDS.
Sleep Advice Has Changed Over Generations
But all the fuss associated with back sleeping often surprises grandparents who raised their own children with the opposite advice.
"My mother-in-law said, 'What do you mean you put her to sleep on her back -- I've never heard of that.'" said Goldman.
But they agreed to disagree with the pediatrician who recommended waking a sleeping baby to eat.
"She was growing and eating and thriving," said Goldman.
"There definitely was a lot of conflicting advice when I first had the baby," said Goldman. "I stopped reading books, they were so overwhelming. One book said do this, and the other said do that -- feed on demand, feed on a schedule, swaddle or don't swaddle."
"What I realized after the anxiety attacks of the first week was, do what makes sense for you and your family," she said. "Trust your instincts as a parent."
Her friend Lindsay Sarnoff did just that.
"When my daughter was a newborn we were going crazy trying to get her to sleep," said Sarnoff, who worked for Ralph Lauren before having her second child this year.
"The first six weeks of her life, she slept on our chest on her tummy," she said. "But it got to the point where we couldn't sleep and it was dangerous if she rolled off."
But one afternoon in frustration, she placed her daughter on her stomach and the baby slept three hours.
"It was genius," Sarnoff said.
Her pediatrician agreed to the day plan, as long as Sarnoff was close by, but not at night. Soon, they put the baby in the bassinette in their bedroom one night with satisfying results.
Now, Sarnoff has a newborn son and "from day one" has put him down on his stomach.
"He's been sleeping well since he was eight days old," she said.
Though she is afraid to confess to her doctor, Sarnoff said she has the support of her own mother.
"My mom says, 'You guys slept on your stomach,'" she said.
But even with risks of head flattening, which in its most severe form can cause the ear to move forward, preventing fluid drainage, doctors are adamant about recommending back sleeping, even during nap time.
Dr. Ari Brown, a pediatrician from Austin, Texas, said the risk of SIDS far outweighs the risk of complications with a flat head.
"The statistics are pretty significant when talking about death," said Brown, author of "Baby 411: Clear Answers and Smart Advice for Babies in the First Year."
"Our parents put us on our bellies and, you bet, we did sleep better -- but at what cost?" she asked.
"The cost for sleeping on their backs is that there are kids who are going to have positional plagiocephaly," Brown told ABCNews.com. "But it's not life-threatening. Which would you choose? And the flat head's not for life."
Brown's patients have seen their flat heads normalized before they enter kindergarten.
"As a pediatrician, I'd rather have a kid with a flat head," Brown said. "We can work with the ear infections."