We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (14 January 2013) and reviewed the reference list of all articles.
SELECTION CRITERIA: Two review authors independently evaluated trials for methodological quality and extracted data.
MAIN RESULTS: Thirty-six randomised controlled trials (8523 women and 12,515 infants) were included.
Progesterone versus placebo for women with a past history of spontaneous
preterm birth Progesterone was associated with a statistically significant reduction in the risk of perinatal mortality (six studies; 1453 women; risk ratio (RR) 0.50, 95% confidence interval (CI) 0.33 to 0.75),
preterm birth less than 34 weeks (five studies; 602 women; average RR 0.31, 95% CI 0.14 to 0.69), infant
birthweight less than 2500 g (four studies; 692 infants; RR 0.58, 95% CI 0.42 to 0.79), use of assisted ventilation (three studies; 633 women; RR 0.40, 95% CI 0.18 to 0.90), necrotising
enterocolitis (three studies; 1170 women; RR 0.30, 95% CI 0.10 to 0.89),
neonatal death (six studies; 1453 women; RR 0.45, 95% CI 0.27 to 0.76), admission to neonatal intensive care unit (three studies; 389 women; RR 0.24, 95% CI 0.14 to 0.40),
preterm birth less than 37 weeks (10 studies; 1750 women; average RR 0.55, 95% CI 0.42 to 0.74) and a statistically significant increase in pregnancy prolongation in weeks (one study; 148 women; mean difference (MD) 4.47, 95% CI 2.15 to 6.79). No differential effects in terms of route of administration, time of commencing
therapy and dose of
progesterone were observed for the majority of outcomes examined.
Progesterone versus placebo for women with a short cervix identified on ultrasound
Progesterone was associated with a statistically significant reduction in the risk of
preterm birth less than 34 weeks (two studies; 438 women; RR 0.64, 95% CI 0.45 to 0.90),
preterm birth at less than 28 weeks' gestation (two studies; 1115 women; RR 0.59, 95% CI 0.37 to 0.93) and increased risk of
urticaria in women when compared with placebo (one study; 654 women; RR 5.03, 95% CI 1.11 to 22.78). It was not possible to assess the effect of route of
progesterone administration, gestational age at commencing
therapy, or total cumulative dose of medication.
Progesterone versus placebo for women with a multiple pregnancy
Progesterone was associated with no statistically significant differences for the reported outcomes.
Progesterone versus no treatment/placebo for women following presentation with threatened preterm labour
Progesterone, was associated with a statistically significant reduction in the risk of infant
birthweight less than 2500 g (one study; 70 infants; RR 0.52, 95% CI 0.28 to 0.98).
Progesterone versus placebo for women with 'other' risk factors for
preterm birth Progesterone, was associated with a statistically significant reduction in the risk of infant
birthweight less than 2500 g (three studies; 482 infants; RR 0.48, 95% CI 0.25 to 0.91).
AUTHORS' CONCLUSIONS: