A Steroid Shot Before Late Preterm Birth: What the ALPS Trial Found

For Families and General Readers

Premature Birth Is Most Common Near the End of Pregnancy

Most people imagine premature birth as happening very early — at 24 or 28 weeks. But the most common type of premature birth is "late preterm" — at 34 to 36 weeks of pregnancy. Late preterm babies represent about 70% of all premature births globally [1], and with roughly 14.9 million premature births occurring worldwide each year [2], the numbers are enormous.

These babies look almost like full-term infants — they weigh several pounds and are relatively developed. But they're still meaningfully more vulnerable than babies born at 40 weeks. A 2007 study by the American Academy of Pediatrics formally recognised this, calling late preterm babies "a population at risk" for breathing difficulties, temperature problems, feeding challenges, and jaundice [3].

The ALPS Trial: Testing Steroids at 34-37 Weeks

For women facing preterm birth before 34 weeks, doctors have given a steroid injection (betamethasone) since the 1970s [4] to speed up the baby's lung development before birth. This works dramatically well, and the evidence from 18 clinical trials was summarised by Crowley in 1995 [3] — finding consistent, large reductions in breathing problems across multiple countries.

The question the ALPS trial asked was: does this also help at 34-36 weeks?

The ALPS trial enrolled 2,831 pregnant women at 34 to 36 5/7 weeks who were likely to deliver within a week [5]. Half received betamethasone; half received a placebo. This was a rigorous, double-blind, randomised trial conducted across multiple US hospitals.

What They Found

Breathing problems were reduced. In the steroid group, 11.6% of babies needed respiratory treatment after birth, compared with 14.4% in the placebo group [5]. That's a real reduction — roughly 1 in 35 late preterm babies benefit.

Blood sugar problems increased. Babies whose mothers received betamethasone had higher rates of hypoglycaemia (low blood sugar): 24% versus 15% [5]. This is a known side effect of steroids suppressing insulin production in the baby. It requires blood sugar monitoring after birth.

At 6-7 years, no difference in developmental outcomes was found between the two groups, providing reassurance that the steroid injection doesn't affect brain development in late preterm babies [5].

What This Means in Practice

The ALPS evidence supports giving betamethasone to women at 34-37 weeks who are likely to deliver within a week — but not to all women approaching their due date. The benefit is real but modest, and the hypoglycaemia risk is real too [5]. Your care team will consider both sides of this equation based on your specific situation.

A complementary injection — magnesium sulphate — is given in many settings to protect the baby's brain before any preterm birth before 34 weeks, based on strong evidence from multiple trials [6]. These two treatments can be given together when both are indicated.

The late preterm period accounts for roughly 70% of all premature births worldwide. With approximately 14.8 million premature babies born globally each year [7], late preterm deliveries represent by far the largest subgroup, and the ALPS finding has direct implications for families across every country. The WHO has recognised antenatal corticosteroids as a priority care item for births before 34 weeks [8]; ALPS now brings evidence for the 34-37 week window that was previously missing. For families, the key message is practical: betamethasone helps the lungs but requires monitoring for low blood sugar, a complication the baby's nursing team will watch closely [9]. The broader context of what it means to be born late preterm — a population with measurably higher risks than full-term babies for breathing, feeding, temperature, and jaundice problems [10] — is what makes that monitoring so important.

References

  1. Chawanpaiboon S, Vogel JP, Moller A-B, et al. Global, Regional, and National Estimates of Levels of Preterm Birth in 2014. Lancet Glob Health. 2019;7(1):e37-e46. doi:10.1016/S2214-109X(18)30451-0
  2. Stoll BJ, Hansen NI, Bell EF, et al. Trends in Care Practices, Morbidity, and Mortality of Extremely Preterm Neonates, 1993-2012. JAMA. 2015;314(10):1039-1051. doi:10.1001/jama.2015.10244
  3. Crowley PA. Antenatal Corticosteroid Therapy: A Meta-Analysis of the Randomized Trials, 1972 to 1994. Am J Obstet Gynecol. 1995;173(1):322-335. doi:10.1016/0002-9378(95)90222-8
  4. Liggins GC, Howie RN. A Controlled Trial of Antepartum Glucocorticoid Treatment for Prevention of the Respiratory Distress Syndrome in Premature Infants. Pediatrics. 1972;50(4):515-525. PMID:4561295
  5. Gyamfi-Bannerman C, Thom EA, Blackwell SC, et al. Antenatal Betamethasone for Women at Risk for Late Preterm Delivery. N Engl J Med. 2016;374(14):1311-1320. doi:10.1056/NEJMoa1516783
  6. Crowther CA, Middleton PF, Voysey M, et al. Assessing the Neuroprotective Benefits for Babies of Antenatal Magnesium Sulphate. PLoS Med. 2017;14(10):e1002398. doi:10.1371/journal.pmed.1002398
  7. Chawanpaiboon S, Vogel JP, Moller A-B, et al. Global, Regional, and National Estimates of Levels of Preterm Birth in 2014. Lancet Glob Health. 2019;7(1):e37-e46. doi:10.1016/S2214-109X(18)30451-0
  8. World Health Organization. WHO Recommendations for Care of the Preterm or Low-Birth-Weight Infant. Geneva: WHO; 2022.
  9. Gyamfi-Bannerman C, Thom EA, Blackwell SC, et al. Antenatal Betamethasone for Women at Risk for Late Preterm Delivery. N Engl J Med. 2016;374(14):1311-1320. doi:10.1056/NEJMoa1516783
  10. Engle WA, Tomashek KM, Wallman C. Late-Preterm Infants: A Population at Risk. Pediatrics. 2007;120(6):1390-1401. doi:10.1542/peds.2007-2952