Antenatal corticosteroid betamethasone administration significantly reduces the risk of neonatal respiratory morbidity in women with twin pregnancies at risk of late preterm delivery, according to the ACTWIN* trial presented at SMFM 2025. 

Since 2016, the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine have recommended antenatal corticosteroid for women with a singleton pregnancy between 34 0/7 and 36 6/7 weeks at imminent risk of preterm birth within 7 days. [BMC Pregnancy Childbirth 2022;22:904]

Recently, it has been suggested that antenatal corticosteroids may also be effective in singleton late preterm pregnancies, and guidelines recommend the use of corticosteroids in singleton pregnant women who are at risk of late preterm birth. [BMC Pregnancy Childbirth 2019;19:114]

“However, the effectiveness of antenatal corticosteroids in twin pregnant women at risk of late preterm birth has not been evaluated, and there is a paucity of [data] in this population,” said Dr Seung Mi Lee from the Department of Obstetrics and Gynaecology at Seoul National University College of Medicine, Korea.

The ACTWIN study enrolled 831 women with twin pregnancies (mean gestational age 36.1 weeks) at risk of late preterm birth. Participants were randomized to receive either an antenatal corticosteroid (betamethasone 12mg, 3mL intramuscular [IM]; n=410) or placebo (normal saline 3mL IM; n=402) twice 24 hours apart.

Among 1,620 neonates, those born to mothers who were administered betamethasone had a significantly lower risk of severe respiratory morbidity within 72 hours after birth, the primary endpoint of the study, than those who were given placebo (4.8 percent vs 7.5 percent; relative risk [RR], 0.64; p=0.038). [SMFM2025, abstract 1]

No perinatal deaths within the first 72 hours of delivery were reported in either treatment group.

In terms of other neonatal outcomes, the betamethasone group had a lower rate of mild respiratory morbidities compared with the placebo group (5.4 percent vs 8 percent; RR, 0.68; p=0.063), including CPAP** use for ≥2 hours (3.4 percent vs 6 percent; RR, 0.58; p=0.031), transient tachypnoea [TTN] of the newborn (2 percent vs 4.2 percent; RR, 0.47; p=0.021), and feeding difficulty (1 percent vs 2.7 percent; RR, 0.38; p=0.023).

However, hypoglycaemia (glucose <40 mg/dL) occurred more frequently with betamethasone than with placebo (15.6 percent vs 11.7 percent; RR, 1.33; p=0.039).

As for maternal complications, the risk of sepsis or maternal chorioamnionitis did not differ between the treatment groups.

“Overall, treatment with an antenatal corticosteroid reduced the risk of severe neonatal respiratory morbidity compared with placebo in late preterm twin pregnancy, … as well as the risks of other respiratory morbidities such as CPAP use for ≥2 hours and TTN,” said Lee.

“In late preterm twin pregnancies, antenatal betamethasone administration is recommended,” she concluded.