Preterm birth: Does it help the baby if the mother takes corticosteroids before the birth?

When a baby is at risk of being born too early, one course of antenatal corticosteroids can help the baby's lungs to develop more quickly. This reduces the risk of the baby dying or having serious complications.

Preterm or premature birth is when a baby is born before 37 completed weeks of pregnancy. Babies who are born very early can have trouble breathing because their lungs are not properly developed. Corticosteroids are drugs which are a synthetic form of human hormones. Around the time between 26 and 33 weeks of pregnancy, these drugs can work like a trigger on an unborn baby's lungs, speeding up their development. It will reach the baby's lungs if the mother is given an injection before the baby is born, and as little as one day's worth of the drug could make a difference. You can read more about corticosteroids and preterm birth in our fact sheet.

Researchers from the Cochrane Collaboration searched for good-quality clinical trials about the use of corticosteroids before birth (called antenatal or prenatal corticosteroid therapy). They looked particularly at how many babies died and how many had serious complications.

The researchers found 21 suitable trials that could help answer their questions. The trials included more than 3,800 women who were likely to give birth prematurely. Some of the women gave birth to twins or more than two babies at the same time. This meant that the researchers could study some outcomes in over 4,200 babies.

The combined results of the trials showed that treatment with antenatal corticosteroids reduced the number of babies who were born alive but died within a few weeks after birth (neonatal deaths). Out of every 1,000 mothers who took corticosteroids, an additional 47 babies lived.

Sometimes babies have serious breathing problems at birth. The medical term for this is respiratory distress syndrome (RDS). All of the 21 trials reported this information and showed that the percent of births where a baby had respiratory distress was reduced from 26% to just over 17% when the mothers had taken corticosteroids. This means that serious breathing difficulties at birth were avoided in an additional 9 out of every 100 babies.

Another serious risk to preterm babies is bleeding in the brain (cerebral or intraventricular haemorrhage). Corticosteroids before birth reduced this risk from 11 out of every 100 babies (11%) down to 6 out of every 100 (6%). Babies whose mothers had taken corticosteroids were also half as likely to get necrotising enterocolitis (NEC), a dangerous inflammatory disease that harms the baby's bowel. The risk was reduced from just over 6% down to 3%.

For the baby, there did not appear to be a risk of major harm from the corticosteroids. Where longer term outcomes for the children were available, it did not appear as though the children's growth or development had been harmed by the corticosteroids their mother took before they were born.

There is some concern that multiple courses of corticosteroids might cause some harm. One course usually consists of at least two injections in one day. That potential risk could be avoided by taking only one course of corticosteroids or possibly by taking lower doses if further courses are used.

A single course of corticosteroids did not appear to have any immediate drug adverse effects for the mother. However, more of the women who took the corticosteroids had sepsis (a serious bacterial infection) after the birth. More research is needed to be sure whether this was a coincidence or whether corticosteroids in fact increase the risk of sepsis.

Babies benefited from their mothers taking corticosteroids, even if it was only one day before the birth. Antenatal corticosteroid therapy was also effective in mothers who had high blood pressure (hypertension) or whose waters had broken some time before the birth (premature rupture of the membranes).


Author: German Institute for Quality and Efficiency in Health Care (IQWiG)

© IQWiG (Institute for Quality and Efficiency in Health Care)