Antenatal Betamethasone for Late Preterm Pregnancies

POEM:  Antenatal betamethasone beneficial to late preterm newborns

Clinical Question:
Does antenatal betamethasone given at 34 to 36 6/7 weeks of
gestation improve outcomes for late preterm newborns?

Bottom Line:
Betamethasone administered to women at risk for late preterm birth reduces
newborn respiratory complications, but with an increase in neonatal
hypoglycemia. There was no evidence for maternal harm. (LOE = 1b)
Gyamfi-Bannerman C, Thom EA, Blackwell SC, et al, for the NICHD
Maternal–Fetal Medicine Units Network. Antenatal betamethasone for women at
risk for late preterm delivery. N Engl J Med 2016;374(14):1311-1320.
This was a randomized double-blind placebo-controlled trial of
betamethasone administered at 34 to 36 6/7 weeks of gestation to women (N =
2831) at high risk for late preterm birth. High risk for late preterm birth
was defined as preterm labor with intact membranes and at least 3-cm
dilation or 75% effacement, or spontaneous rupture of membranes, or
expectation of indication for delivery for any other reason between 24
hours and 7 days after randomization. The authors excluded women who had
already received antenatal corticosteroids, were expected to deliver within
24 hours, had chorioamnionitis, or had uncertain gestational age.
Approximately 60% of each group received the 2 prescribed doses of
betamethasone 12 mg or placebo 24 hours apart, while most of the remaining
women gave birth before the second dose could be administered. The primary
outcome was a composite of respiratory support within 72 hours after birth,
stillbirth, and neonatal death. Respiratory support included continuous
positive airway pressure or high-flow nasal cannula for at least 2
continuous hours, supplemental oxygen of at least 0.30 for at least 4
continuous hours, extracorporeal membrane oxygenation, or mechanical
ventilation. There was a significant reduction in the rate of the primary
outcome in the treated group (11.6% vs 14.4%; relative risk [RR] 0.80, 95%
CI 0.66 – 0.97; number needed to treat = 35, 19 – 259). Rates of transient
tachypnea of the newborn, bronchopulmonary dysplasia, neonatal
resuscitation, and surfactant use were significantly reduced in the treated
group. Infants in the treated group were also less likely to spend 3 days
or more in intensive or intermediate care nursery and had shorter time
until first feeding. There was a higher incidence of hypoglycemia in the
treated group (24% vs 15%; RR 1.60, 1.37 – 1.87; number needed to treat to
harm = 11, 8 – 16). There were no significant differences in many other
secondary outcomes, including neonatal sepsis, necrotizing enterocolitis,
and others. There were also no differences in maternal outcomes, including
rates of chorioamnionitis, endometritis, cesarean delivery, and time to

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