June 18, 2014 at 1:45 AM ET
Today's expectant moms and their doctors have decided it's not nice to fool Mother Nature. Rather than inducing labor, they're letting nature take its course, with the length of pregnancies in the U.S. on the upswing, according to a new study by the CDC.
The study released Wednesday tracks labor started through surgical or medical means during the years 2006 through 2012. The researchers found that induction rates at 38 weeks — once considered full-term gestation but now called an early-term gestation — declined for 36 states and the District of Columbia during this six-year period. Declines ranged from 5 percent to 48 percent.
Geography didn’t seem to matter. Thirty-one states and the District of Columbia posted declines of at least 10 percent. The researchers did find that trends in induction rates at each week from 35 weeks, considered late pre-term, to 38 weeks, varied by maternal age. At 38 weeks, though, induction rates declined for all maternal age groups under 40, dropping 13 percent to 19 percent for women in their 20s and 30s.
This is a sharp reversal of trends tracked from 1981 through 2006 in which the proportion of babies born at less than 39 weeks gestation increased nearly 60 percent, while births at 39 weeks or more declined more than 20 percent.
“We were surprised that the overall induction rate went down,” says lead researcher Michelle Osterman, a health statistician with the National Center for Health Statistics, which is part of the CDC.
And it is welcome news, too. “For years we were taught that the 37th or 38th week of pregnancy was full term, but we did not appreciate the neonatal outcomes,” says ob/gyn Dr. Nancy Cossler, vice chair for quality and patient safety at University MacDonald Women’s Hospital in Cleveland, Ohio.
“It was an ingrained part of our culture that 37 weeks is OK, but it’s not necessarily OK for the baby,” she says, citing issues such as hypothermia, feeding difficulties and respiratory distress among infants born early.
Historically, MacDonald Women’s Hospital had a rate of about 11 percent for labor induction for non-medical reasons among patients who were 37 to 38 weeks pregnant. Today, it’s nearly zero. In 2013, only one birth among the 37 to 38 week gestational age was done through induction. The patient had metastatic breast cancer, which is not among the usual listed criteria for medical induction, and needed to start chemotherapy and needed an early delivery, says Cossler.
Indeed, there is a big push nationally for longer-term births, such as the large-scale educational program called the 39-Week Initiative, supported by the March of Dimes and other groups. It seeks to end non-medically indicated deliveries prior to 39 weeks. Last year, the American Congress of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine even recommended the label “term” in pregnancy, be replaced with categories based on gestational age. Today, babies born at 39 weeks through 40 weeks and six days of pregnancy are considered “full term.” Babies born at 37 to 38 weeks are now considered “early term.”
“I think this study is very positive since several of us have now provided evidence that babies have better outcomes (with longer term births),” says Dr. Kimberly Noble, assistant professor of pediatrics at Columbia University.
In a study published in the journal Pediatrics of 128,000 New York City public school children, Noble and her colleagues found that compared to children born at 41 weeks, those born at 37 weeks had a 33 percent increased chance of having third-grade reading problems, and a 19 percent increased chance of having moderate math issues.
But doctors do worry that the pendulum could swing too far and patients may be afraid of induced deliveries.
Our study “can’t differentiate between induction done for medical reasons and induction done for convenience, and if your doctor says this baby needs to come out at 37 weeks because of a problem, you need to trust your doctor,” says Noble, citing issues such as maternal or fetal distress as a cause for earlier delivery. What patients and doctors shouldn’t do is schedule an earlier delivery because of a vacation or other issue. “We know that 39 weeks and beyond is good for the baby,” she says.