MEDLINE and SCOPUS searches, including
references of the retrieved articles and additional
automated search using the ‘search for related articles’
PubMed function, were used. Randomized controlled
trials assigning women at risk for preterm birth to
progesterone or placebo were included (both singleton
and multiple pregnancies). Outcomes were neonatal
and perinatal death, respiratory distress syndrome
(RDS), retinopathy, necrotizing enterocolitis (NEC),
intraventricular hemorrhage (IVH) Grade 3–4, sepsis,
admission to the neonatal intensive care unit (NICU) and
composite adverse outcome