Before preterm birth: What do steroids do?
If a baby is at risk of being born too early, giving the mother steroids before the birth can help her unborn baby's lungs to develop more quickly. This reduces the risk of serious complications or the newborn dying.
Preterm birth is when a baby is born before 37 completed weeks of pregnancy. Babies who are born very early may have trouble breathing because their lungs aren’t yet fully developed. For this reason, it’s important to give the mother steroid medication before the birth: Steroids help the unborn child’s lungs develop more quickly.
There is a lot of research on the possible benefits and harms of this treatment, which is sometimes called antenatal steroid treatment. As little as one day of treatment can make an important difference.
How can steroids help the baby?
Steroid drugs, also known as corticosteroids, are synthetic forms of natural human hormones. When pregnant women are given steroid injections, the medication travels to the baby’s body and lungs through their bloodstream. One “course” of antenatal steroid treatment usually consists of two injections given 24 hours apart.
When used between 25 and 33 weeks of pregnancy, steroids can speed up the development of the baby's lungs a lot. This gives many preterm babies a much better chance of survival. A total of 30 studies involving around 7,800 women looked at the effects of this treatment. The proven benefits of antenatal steroid treatment for the child include:
A better chance of survival:
- Without antenatal steroid treatment, about 10 out of 100 preterm babies die within a few weeks of being born.
- With antenatal steroid treatment, about 7 out of 100 preterm babies die within a few weeks of being born.
In other words, antenatal steroid treatment can prevent the deaths of about 3 out of 100 preterm babies within the first few weeks of birth.
Lower risk of serious breathing problems:
- Without antenatal steroid treatment, about 18 out of 100 preterm babies have serious breathing problems.
- With antenatal steroid treatment, about 12 out of 100 preterm babies have serious breathing problems.
In other words, the treatment can prevent serious breathing problems after birth in about 6 out of 100 preterm babies.
Much lower risk of bleeding in the brain:
- Without antenatal steroid treatment, about 12 out of 100 preterm babies have bleeding in the brain.
- With antenatal steroid treatment, roughly 6 out of 100 preterm babies are affected.
So the treatment prevents this kind of bleeding in about 6 out of 100 children.
Lower risk of a serious bowel condition called necrotizing enterocolitis (NEC):
- Without antenatal steroid treatment, about 6 out of 100 preterm babies have this bowel condition.
- With antenatal steroid treatment, about 3 out of 100 preterm babies are affected.
In other words, the treatment prevents NEC in about 3 out of 100 preterm babies.
Even one single course of steroid treatment can help the child's lungs work better after he or she is born.
A second course of steroid treatment might be considered if the birth can be delayed by more than a week after the first course was given. A total of 10 studies, involving about 4,700 women, looked into the effects of a second course of steroid treatment. These studies show that a second course can have benefits too: It lowers the risk of breathing problems and other serious consequences even further.
What side effects does steroid treatment have?
When pregnant women took a single course of steroids, no adverse effects were observed in the newborns. Studies that followed the development of preterm babies into childhood or adulthood did not find any clear differences in growth and development between those who received steroids before birth and those who did not.
Side effects are more likely if more than one course of steroid treatment is given. Shortly after being born, children who have more than one course are somewhat smaller than children who only have one course. But they “catch up” in size within a few months. The studies didn’t find any evidence of long-term negative consequences.
Steroid treatment hasn’t been found to have any serious side effects in pregnant women either. About 1 out of 100 women who have a second course of steroid treatment have temporary sleep problems shortly after giving birth. But many women who don’t have steroid treatment have sleep problems after pregnancy and a preterm birth too.
Crowther CA, McKinlay CJ, Middleton P, Harding JE. Repeat doses of prenatal corticosteroids for women at risk of preterm birth for improving neonatal health outcomes. Cochrane Database Syst Rev 2015; (7): CD003935.
Roberts D, Brown J, Medley N, Dalziel SR. Antenatal corticosteroids for accelerating fetal lung maturation for women at risk of preterm birth. Cochrane Database Syst Rev 2017; (3): CD004454.
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