Expectant mothers over the age of 40 are at a much higher risk of stillbirth than younger women, U.S. researchers have found.
It's long been known that older mothers are at an increased risk of pregnancy complications, such as gestational diabetes, preeclampsia, and intrauterine growth restriction. But the researchers wanted to see if age alone, rather than a health problem in a previous pregnancy, affected the risk of babies dying in utero or at birth.
"We wanted to investigate if this is an independent risk," the author of the study, Dr. Mert Ozan Bahtiyar of the Yale University School of Medicine, told Canada AM.
"After excluding all the medical risk factors and congenital abnormalities, we were still able to show that with increasing maternal age, the stillbirth rate was significantly higher.
"And this was very high especially at mothers 40 years and older."
The researchers looked at over 11 million babies born in the U.S. to women aged 15 to 44 between 1995 and 1997. When maternal complications and congenital abnormalities in the fetus were excluded, six million babies remained.
They then looked at data from the US Centers for Disease Control, which registered the deaths of babies.
They calculated that women aged 40 to 44 had three times the risk of stillbirth than women aged 25 to 29.
While the data is limited to mothers in the U.S., it affects many women in Canada who are having babies older in life.
Statistics Canada says almost one-half of the women who gave birth in 2003 were aged 30 and older. That's a big jump from two decades ago, when three-quarters of moms in Canada were under 30 years old.
A normal pregnancy is 40 weeks long and obstetricians generally do not perform fetal testing until after the 41st week of gestation, as this is the time when fetal death risk is heightened.
The researchers found that fetal checks at 38 weeks of pregnancy had the greatest impact on reducing stillbirth rates in older women.
These checks include listening to the baby's heartbeat and testing the amniotic fluid to pick up any signs of distress.
"The fetal heart rate tracing, the non-stress test, is an indicator of fetal wellbeing, and probably it is one of the best tools we have in our hands," says Dr. Bahyiyar.
"It is not without any drawbacks, but that is the best thing.
"So if a mother starts to be tested at around 38 weeks or so and any concern is noted in the testing, then she can be induced and she can be delivered in a timely manner and this could prevent stillbirth."
The Yale University study is being presented to the Maternal-Fetal Medicine Conference in San Francisco.
