By Karen Weintraub
Don’t be too eager to deliver that baby.
Doctors have long viewed babies born at 37 or 38 weeks as full term, but new research suggests that infants are better off staying in a healthy womb longer, if possible.
A study published this morning in Pediatrics found that babies born at 37 or 38 weeks scored slightly but significantly worse on third grade English and math tests than their counterparts born at 39-41 weeks. A typical pregnancy is 40 weeks.
The study has implications for doctors and parents who often choose to have early deliveries for the sake of convenience or at the slightest hint of any problem with the pregnancy.
The womb really is the best place for an infant, said Dr. Jonathan Davis, chief of Newborn Medicine at The Floating Hospital for Children at Tufts Medical Center, who was not involved in the research.
“The message is: unless you really feel that there’s an irreversible or really dangerous thing going on, you should wait until at least 39 weeks to deliver,” he said.
Doctors often encourage earlier deliveries to avoid problems during birth, Davis said. “I really believe the reason they intervene so often is because they’re worried about getting sued.” But this and other recent research suggests doctors need to take a longer view.
“The fetal brain is always developing. This has been apparent before this study, when we think about how much harder it is to breastfeed a baby born before 39 weeks,” said Dr. Tamara C. Takoudes, a specialist at Boston Maternal Fetal Medicine, a private practice with offices across the region.
Harvard hospitals decided about 10 years ago to start delivering some babies via C-section at 38 weeks to improve scheduling flexibility and spread out operating room demand, said Takoudes, a clinical instructor at Harvard Medical School. A few years ago, the hospitals, including Beth Israel Deaconess Medical Center where Takoudes delivers, went back to the 39-week rule after data suggested more babies were ending up in intensive care, she said.
The new study looked at the birth records of 128,000 babies born in New York City between 1988 and 1992, and the third grade test scores of those babies 8 years later. It found that babies born at 37 or 38 weeks scored slightly lower on tests than those born at 39-41 weeks. There were also more children in the earlier birth group who scored significantly below their peers.
The study didn’t prove that early birth caused those lower scores – it’s possible that some common factor caused both, said Dr. Kimberly Noble, an assistant professor of pediatrics at Columbia University Medical Center and New York-Presbyterian Hospital, and an author of the paper.
Noble said researchers tried to account for all the factors they could, such as socioeconomics, birth weight, age of mother, C-section rate, mother’s smoking history and whether the mother was born in the United States (half of them were). The study looked only at New York City, which is poorer and more diverse than the rest of the country, but other studies found similar results in Denmark, Belarus, Switzerland, and Scotland.
Why have American doctors thought it was okay to deliver at 37 or 38 weeks?
Noble thinks it’s because babies at that age are physically mature and can usually leave the hospital within a few days of birth.
Parents who do have to deliver at 37 or 38 weeks shouldn’t worry at all about their newborn’s eventual third grade math and English scores, Noble said. There’s plenty of time to make up whatever small deficit may happen from delivering a week or two early.
“A child born earlier within the term may have a somewhat higher risk of academic problems, but it’s certainly not inevitable,” said Noble, who is currently nursing her own newborn, delivered at full term. “There are a slew of things that parents could do to buffer results of earlier term birth.”