Giving corticosteroids to women at risk of preterm birth at 34 weeks of pregnancy or later reduced the risk of severe breathing problems in the baby after birth from 1.9% to 1.1%. Steroids also reduced the risk for babies born by planned caesarean section after 37 weeks (so not premature).
Steroids are known to be beneficial if given to pregnant women at risk of preterm birth before 34 weeks and are already advised for babies born by caesarean section. This meta-analysis of six large trials provides new evidence that steroids might also benefit premature babies born after the 34th week. However, the review also found steroids increased the risk of low blood sugar in the new-born, which would need monitoring.
The risks and benefits need to be considered before further recommendations can be made extending the use of antenatal corticosteroids to this late preterm age. This includes exploring the long-term effects and consequences for specific groups of women such as those with diabetes or pregnant with more than one baby.
Why was this study needed?
In the UK, about one baby in every 13 is born prematurely, before 37 weeks of pregnancy. Preterm new-borns, particularly those born before 34 weeks of pregnancy, are at high risk of respiratory distress syndrome. They may need help to breathe and can be at risk of long-term problems such as learning difficulties.
Giving corticosteroids to women at risk of preterm labour helps the unborn baby’s lungs to mature quicker and reduces the chance of respiratory distress syndrome.
To date evidence has suggested that antenatal corticosteroids give most benefit if the baby is between 26 and 34 weeks plus six days of pregnancy. There has been uncertainty whether antenatal corticosteroids could benefit late preterm babies, born at 34 weeks or later. This is what this review aimed to address. It also looked at outcomes for babies born by planned caesarean section at 37 weeks of pregnancy or more.
What did this study do?
This systematic review and meta-analysis identified six randomised controlled trials involving 5698 women who were pregnant with one baby. The trials compared the use of antenatal corticosteroids with placebo or no treatment. Four trials used the corticosteroid betamethasone and two used dexamethasone, both given my muscular injection.
Three trials (3200 women) examined the effect of steroids in babies born between 34 and 36 weeks plus six days of pregnancy. The other three trials (2498 women) included babies born by planned caesarean at 37 weeks of pregnancy or later.
The researchers’ main outcome of interest was severe respiratory distress, but none of the individual trials were reported to have assessed this as their main outcome.
Most of the trials had a low risk of bias. Only one trial was carried out in the UK.
What did it find?
- Antenatal corticosteroids reduced risk of severe respiratory distress in babies delivered at 34 weeks or later (vaginally or by caesarean section). This occurred in 1.1% of babies whose received antenatal corticosteroids compared with 1.9% who didn’t (relative risk [RR] 0.55, 95% confidence interval [95% CI] 0.33 to 0.91). Four trials had examined this outcome.
- Antenatal steroids also reduced risk of overall respiratory distress syndrome in babies born at 34 weeks or later. The condition at any level of severity from mild to severe developed in the babies of 5.5% of treated mothers compared to 7.2% of untreated (RR 0.74, CI 0.61 to 0.91). These results were from meta-analysis of all six trials.
- In the three trials of babies delivered vaginally between the start of 34 weeks and 36 weeks plus six days, antenatal corticosteroids also reduced risk of severe respiratory distress syndrome, which developed in 1.4% compared with 2.2% (RR 0.60, 95% CI 0.33 to 0.94).
- Babies delivered by planned caesarean section at 37 weeks had reduced risk of overall respiratory distress syndrome if their mother received corticosteroids (2.7% vs. 6.7%, RR 0.40, 95% CI 0.27 to 0.59).
- The three trials of babies delivered between 34 and 36 weeks plus six days found that antenatal corticosteroids increased risk of low blood sugar in the new-born. This complication occurred in 22.8% compared with 14.2% of babies whose mothers didn’t receive antenatal corticosteroids (RR 1.61, 95% CI 1.38 to 1.87).
- Antenatal corticosteroids had no effect on risk of new-born death.
What does current guidance say on this issue?
The Royal College of Obstetricians and Gynaecologists recommend that antenatal corticosteroids are offered to women between 24 and 34 weeks plus 6 days of pregnancy who are at risk of preterm birth (spontaneous or induced). Use prior to 24 weeks is only considered by senior doctors.
The guidelines do not give a recommendation on use of corticosteroids for risk of spontaneous birth after 34 weeks of pregnancy. However, they do recommend that corticosteroids be given to all women up to 38 weeks plus six days of pregnancy for whom an elective caesarean section is planned.
What are the implications?
Antenatal corticosteroids might benefit late preterm babies born after 34 weeks, as well as those born earlier. It could mean fewer babies need respiratory support and leave hospital sooner, with reduced risk of associated complications.
However, the mixed findings by pregnancy age and low outcome rates – particularly for severe respiratory distress – combined with the risk of low blood sugar, limit the strength of conclusions. There is no evidence on the long-term effects, or the effects in specific groups of women, such as those pregnant with multiple babies. These issues need to be clarified before further recommendations can be made.
Citation and Funding
Saccone G, Berghella V. Antenatal corticosteroid for maturity of term or near term foetuses: systemic review and meta-analysis of randomized controlled trials. BMJ. 2016;355:i5044
This study received no funding.
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