Just let me make it to 36 weeks, Colleen Carroll prayed when she went into premature labor in her 33rd week of pregnancy. If only she could delay childbirth a while longer, she believed, her baby would be fine.
On Jan. 8, one day short of 36 weeks, little Caitlin came into the world screaming. Carroll cradled her brown-haired daughter in her arms, thinking, "Thank God."
Then she noticed the baby was making odd, grunting noises.
It was respiratory distress. The newborn went alarmingly downhill until doctors stabilized her on a respirator in the neonatal intensive-care unit at Northwestern University's Prentice Women's Hospital. "You think you're in the clear, and then the baby has trouble, and you wonder why," said Carroll, a former Prentice nurse.
A growing body of recent research points to the answer: Babies born in the 34th through 36th week of a woman's pregnancy are at a much higher risk of medical complications than infants delivered at full term, or after 37 weeks.
Although most of these so-called late pre-term infants are healthy, a significant minority -- as many as 17% to 34%, according to a recent report -- have breathing problems, jaundice, feeding difficulties, low blood sugar, unstable body temperatures and other medical issues.
This is by far the largest and fastest-growing group of premature infants born in the U.S.: More than 350,000 are born each year. Experts aren't sure why their numbers are increasing, but they suspect that at least some physicians may be delivering babies early without solid medical justification, thinking the children won't be in danger.
Until the last few years, "no one paid a whole lot of attention to these babies" because they look big and seem almost fully developed, said Dr. Tonse Raju, a neonatal specialist and medical officer at the National Institute of Child Health and Human Development.
Yet even at this late stage, a baby's brain volume is only about 60% of what it should be if born at full term, experts explain. The infant is still laying down fatty tissue that will help insulate him or her after birth. The lungs and guts aren't fully functional, and the liver isn't yet able to process waste adequately.
"The baby is making final preparations to be separated from Mom, and these aren't just niceties: There's important maturation going on," said Dr. Robin Steinhorn, head of neonatology at Northwestern's Feinberg School of Medicine.
A study by researchers from the Centers for Disease Control and Prevention that was published in the November issue of the Journal of Pediatrics underscores the vulnerability of these newborns. It found that infants born at 34 to 36 weeks were six times more likely to die in the first week of life and three times more likely to die in their first year than babies born at full term. Overall, the number of deaths remained small: fewer than three for every 1,000 late pre-term infants.
More commonly, these babies have medical issues that require extra attention and longer stays in the hospital. Of those born at 34 weeks, for instance, as many as three-quarters can find their way to neonatal intensive care, where intravenous tubes provide nutrition and breathing tubes keep oxygen flowing, said Dr. William Engle, a pediatrics professor at the Indiana University School of Medicine.
"Each week in the womb counts," he said, urging doctors and parents to be "vigilant" in monitoring these newborns.
Experts suggest several trends are responsible for the increase in late pre-term births. More couples are becoming pregnant through assisted reproduction, which increases a woman's risk of carrying multiple babies and of going into premature labor. More older women are trying to have children, again increasing the chance of medical complications.
Meanwhile, obstetrical practices have changed, as physicians monitor pregnant women more aggressively and act earlier on potential problems -- a strategy that has significantly reduced stillbirths and neonatal deaths. Obstetricians also may be more willing to deliver early because of medicine's extraordinary advances in caring for premature babies.
Of particular concern to experts are anecdotal reports that some babies are delivered early without strong medical justification. If an anxious mom wants to end an uncomfortable pregnancy, a doctor may agree.
"It may not be happening in every hospital or every obstetrics practice, but it's happening enough to warrant significant concern," said Dr. Alan Fleischman, medical director of the March of Dimes, which is investigating the issue in a study that has not been published.
Dr. Sarah Kilpatrick, head of the division of maternal fetal medicine at the University of Illinois at Chicago Medical Center, said she believed there were doctors who would deliver women as much as a month early for "relatively minor reasons," such as a slight increase in the mother's blood pressure. "We don't do that," she added.
"There are women who will tell me, if you won't deliver me here I'll fly to New York City there and do it there at 36 weeks," said Dr. Jay Iams, professor of maternal fetal medicine at Ohio State University Medical Center.
Few doctors succumb to this kind of pressure, Iams said. But if the woman is in what he calls "the gray zone" -- for instance, she has some degree of hypertension or experienced a complication during an earlier birth or reports the baby isn't moving much -- a physician may well decide "What am I waiting for?" and schedule a delivery.
In light of new research, physicians may want to reconsider how they weigh the benefits of scheduling caesarean sections or inducing women against the potential health risks for late pre-term infants, said Dr. Lucky Jain, a pediatrics professor at Emory University Medical Center in Atlanta.
Sheila Nalywajko, 27, of Elk Grove Village didn't have a choice when her third son, Nathan, was born at 34 weeks in mid-December. Both of his older brothers had been delivered early because of serious medical complications.
This time, physicians at the University of Illinois at Chicago Medical Center scheduled a C-section six weeks early after struggling unsuccessfully to control Nalywajko's soaring blood pressure. Though Nathan was a healthy 6 pounds at birth, he couldn't breathe on his own and had dangerously high blood pressure in vessels around his lungs. He spent three weeks in neonatal intensive care.
"You think you know what to expect -- and you're wrong," said Nalywajko, who said she wasn't prepared for Nathan's medical problems despite her earlier experiences. "You think my other kids, they were OK, so let's go ahead and do this. But it was terrible, what he went through in those first few weeks."