Even at 37 Weeks, Babies are Developing
By the time you reach the home stretch of your pregnancy, you're ready to be done with it. You're tired, you're swollen, your back aches, and, most of all, you want to see your baby. In those last few weeks, you might even be talking to your doctor about scheduling a C-section or an early induction, particularly if you're having problems with your pregnancy.
Until recently, babies born at 37 weeks were considered to be safely at full term. "People thought those last few weeks didn't matter," says John Thorp, M.D., professor of obstetrics and gynecology at the University of North Carolina at Chapel Hill School of Medicine. "If the baby would do well and Mom was tired of being pregnant, why not end it early?" Even at 34 weeks, infants were thought to be at low risk, largely because their lungs are usually fully developed by then.
However, new studies indicate that these deliveries done ahead of schedule are harmless after all. Even if an early baby is fully able to breathe on his own, he's still at higher risk for a wide range of health and developmental problems, some of them long-lasting. Most surprising is the finding that every day of development matter, right up to the end. In fact, the American College of Obstetricians and Gynecologists (ACOG) now advises doctors to avoid scheduling deliveries before 39 weeks unless the mother or child is in danger.
Why the last weeks matter
In a January 2009 study coauthored by Dr. Thorp, more than 15 percent of newborns delivered by C-section at 37 weeks experienced at least one medical problem, compared with just 8 percent of 39-week babies. The researchers found that babies born at 37 weeks were four times more likely than 39-week infants to have breathing problems and about three times more likely to have low blood sugar, a severe bacterial infection, or a hospitalization lasting longer than five days. At 38 weeks, they were still about twice as likely to have one or more of those problems as a baby born a week later. But obvious health problems are just the tip of the iceberg, Dr. Thorp says. "Many early babies don't feed well, don't sleep well, and cause their families all sorts of heartaches," he explains. "It's subtle stuff that doesn't send you to the NICU, but it will impact the beginning of your child's life."
The risks are even higher for babies who arrive between 34 and 36 weeks. As a result, these babies, who once were called "near-term," are now known as "late preterm." Compared with a baby born at 37 weeks, they're four times more likely to have at least one medical condition, such as problems with body-temperature regulation, low blood sugar, respiratory distress, apnea, jaundice, and feeding difficulties, according to ACOG. While those problems may not linger long, researchers from the Centers for Disease Control and Prevention and the March of Dimes found that these infants are six times more likely to die in their first week and three times more likely to die in their first year of life than babies born after 37 weeks. "Fortunately, the overall risk of death is still very low," Dr. Thorp says.
Beyond the immediate medical problems, these deliveries may also be associated with learning disabilities, according to a recent study published in Pediatrics from the University of Florida. The researchers found that healthy late-preterm babies had a 36 percent higher risk of a developmental delay or disability in their first five years of life and were more likely to be held back in kindergarten than babies born after 37 weeks. And recent Stanford University research found that healthy late-preterm infants had lower reading scores through fifth grade and were more likely to need a special-education program in early elementary school than babies born closer to term. Happily, the sooner a child's learning problem is addressed, the more likely she will be able to catch up.
What moms can do
While most babies arrive on their own timetable, it's important for every expectant mom to take these steps based on these new findings.
Never push for an early delivery. Women sometimes ask to schedule their delivery ahead of time in order to book their favorite ob-gyn or to accommodate a family member's travel plans. "A woman might say, 'My mom's coming in from California for the birth,' " explains Alan Fleischman, M.D., medical director of the March of Dimes. "It isn't unusual for doctors to perform a cesarean or an induction on request." His advice? Don't even ask. Unless there's a compelling medical reason to rush, a healthier baby is worth the wait.
Better your odds of going to term. Preventing preterm labor starts before you're pregnant. "That means making sure you're ready for pregnancy by not smoking, drinking, or doing drugs and by managing your weight," says Dr. Fleischman. "If you don't take care of those things before you conceive, then you need to do so as early in your pregnancy as possible." New research also shows that taking folate, a B-vitamin, for a year or longer before becoming pregnant may reduce your risk of having an unplanned preterm birth by 50 to 70 percent.
Consider an earlier maternity leave. A recently published study from the University of California Berkeley found that women who were clerical, managerial, manufacturing, and service workers and who felt their efforts on the job outweighed their compensation were less likely to deliver early if they took maternity leave before giving birth rather than waiting until after the baby's arrival. Several international studies have shown a similar connection. If you have a demanding job or you're under a lot of stress for any reason, experts recommend following your instincts: Schedule breaks or time off whenever you feel the need, and seek out plenty of emotional and physical support from the people around you.
Understand the risks. Most babies who arrive early do so because the mom is having complications with her pregnancy. Problems such as preeclampsia (pregnancy-induced high blood pressure) or placenta previa (when the placenta blocks all or part of the opening to the cervix) may be mild enough that you can safely wait to deliver at term or severe enough that you'll need to deliver right away. For situations that fall somewhere in between, you and your doctor will need to weigh the pros and cons of delivering sooner rather than later. The reassuring news is that thanks to all of this new research, your baby's pediatrician will be better prepared to give her any extra care she might need if an early birth turns out to be unavoidable.
Get Your Due Date Straight
Your due date plays a big role in the conversation about whether to schedule an induction or a C-section. And the best way to learn the most precise date is to have an ultrasound in your first trimester. "If you're going to be induced at 38 weeks and your date is off by two weeks, you'll have a 36-week baby," says Dr. Alan Fleischman, medical director of the March of Dimes. A first-trimester ultrasound is accurate to within five to seven days. Unfortunately, many women wait to have an ultrasound until the second trimester, when the test is better at detecting abnormalities but much less dependable for dating purposes. While your doctor will also calculate based on the first day of your last period, those results are less reliable if you can't pinpoint that day or have an irregular cycle.
Originally published in the August 2009 issue of Parents magazine.