The decades-old clinical practice of giving multiple courses of steroids to pregnant women at risk of delivering prematurely may actually cause harm to the baby, a new study in the Dec. 20/27 Lancet shows.
“This will be the definitive study on repeated doses,” says John Newnham of the University of Western Australia in Perth. “It’ll profoundly change clinical practice.”
Babies born prematurely often have underdeveloped lungs, leading to respiratory distress and other serious health issues. Doctors know that a single course of steroid hormones given to a pregnant mother, often two doses 24 hours apart, unequivocally hastens lung development, improving the outcome for the baby.
But, currently, women at risk of giving birth early are routinely given numerous rounds of steroid hormones, believed to enhance the development of the lungs even more.
Science News headlines, in your inbox
Headlines and summaries of the latest Science News articles, delivered to your email inbox every Thursday.
Thank you for signing up!
There was a problem signing you up.
“The practice changed before trials could take place,” says Kellie Murphy of the University of Toronto in Canada. “We like to think we have all of the answers, but we don’t.”
Some doctors thought the effectiveness of the single course would wear off if the mother remained pregnant for some time after the treatment. Earlier, smaller studies of human babies suggested that doses of steroids given every 14 days might be more beneficial to the baby’s health than a single course, says Murphy.
But other data offered a conflicting view. Studies in animals have suggested that multiple rounds of steroids may interfere with the development of other organs, like the brain and the pancreas. Regardless, many doctors gave multiple courses of steroids, believing the benefits outweighed the costs.
In the largest study of its kind, Murphy and her collaborators looked at 1,858 pregnant women who were at high risk of giving birth prematurely. All of the women in the study received one course of steroids. Researchers then split the women into two groups: One group received additional courses of steroids every 14 days until delivery or week 33 of pregnancy. Women in the second group received a placebo.
Babies exposed to more doses of steroids weighed less, were shorter and had a smaller head circumference at birth than babies exposed to the placebo, which can affect long-term health. These babies born to women who received multiple rounds of steroids had similar rates of mortality to babies exposed to the placebo.
“The results are clear that we saw no benefit,” says Murphy. But it wasn’t just an absence of benefit, she adds. The researchers found the multiple courses of steroids to be harmful to developing babies.
A study by Newnham in 2004 also found a harmful link between multiple doses and developmental problems. That study of 541 children found kids who were exposed to multiple rounds of steroids while in the womb were more likely to have behavioral problems, including hyperactivity.
Subscribe to Science News
Get great science journalism, from the most trusted source, delivered to your doorstep.
Murphy and colleagues plan to continue monitoring the health and development of the children in the study to look at the long-term effects of steroid exposure in the womb.
“Always in medicine, we try to do no harm. We want to treat people and make things better,” Murphy says. Large, random clinical trials like this one “have the power to change clinical practice.”