Any woman who’s ever been pregnant knows that the last couple of weeks before delivery are some of the most uncomfortable. But, a new study says that -barring medical necessity – if you can stick it out till the baby is 39-40 weeks, the infant’s health will benefit.
Previously it was thought that an infant’s mortality risk was similar for babies born between 37 and 41 weeks. The recent study shows that the risks increase when babies are born between 37 and 39 weeks of gestation, and that this risk decreases with each additional week of pregnancy.
Full-term babies are less likely to have hearing, vision, feeding or birth-weight problems. Those final weeks of a pregnancy also give the lungs, eyes and brain enough time to fully develop. A full term birth is considered to be 39-41 weeks.
“A truly elective delivery should wait until at least 39 weeks,” says study researcher Uma M. Reddy, MD, MPH of the Eunice Kennedy Shriver National Institute of Child Health and Development in Bethesda, Md. ”We don’t stop labor at 37 weeks, and the majority of babies will do fine,” she says. But “if nothing is going on and you are doing well, waiting to 39 weeks is best for you and your baby.”
In 2006, infant mortality was 1.9 deaths for every 1,000 live birth when babies were born at 40 weeks. This rate increased to 3.9 per 1,000 live births when a baby was born at 37 weeks, the study showed. The risks of newborn deaths remain small, but when babies are born before 37 weeks the risks doubles compared to infants born at 40 weeks.
“We need to make people aware that within the definition of term, there are two categories,” says Alan R. Fleischman, MD, the medical director of the March of Dimes in White Plains, N.Y. Term is “a biologic continuum between 37 and 41 weeks and those babies born early in term are different than those babies born at full term,” he says. The new findings apply only to women who do not have medical reason to deliver before 39 weeks, he says. But “there is a whole group of women and doctors who are delivering early for convenience or due to a very minor change in some test that has not been shown to be helpful,” he says. “It is a perfect storm because you never see a mother who likes the last four weeks of pregnancy. It’s uncomfortable and many feel it is time.”
J. Christopher Glantz, MD, MPH, a professor of maternal-fetal medicine at University of Rochester School of Medicine, agrees. “The definition of term is a little arbitrary and it is an old definition based on how babies did many many years ago.” Most babies do OK at 37 weeks, he says. “The differences are not that dramatic between the actual risk of mortality from 37 to 39 weeks, but why take any unnecessary risks at all?”
The findings appear in Obstetrics & Gynecology.
For mothers–to-be, those last few weeks of pregnancy can feel like an eternity. But, if there is no medical reason to deliver early, you’ll be giving your newborn a healthier start in life – if you tough it out.