Table 3 Characteristics of included studies (Non-randomized studies)

Berghella 2009 [27]

USA

Retrospective cohort (January 1998 - December 2005)

222 (n = 68 vs. n = 154)

Women between 14 and 25 week of gestation with suspected cervical dilation ≥1 cm.

Indomethancin plus some with cerclage

No treatment plus some with cerclage

Prolongation of pregnancy >28, 32, or 35 weeks

(50 mg orally, followed by 25 mg orally every 6 h for a maximum of 48 h)

Perinatal death

Birth weight >1500 grams

Cape 2010 [26]

USA

Retrospective cohort (2003–2008)

^a138 neonates (n = 69 vs. n = 69)

All women less than 29 weeks of gestation with threaten with premature rupture of membranes.

Indomethancin

No treatment

Neonatal outcomes only including intraventricular hemorrhage, necrotizing enterocolitis, patent ductus arteriosus, and spontaneous intestinal perforations

Manuck 2012 [25]

USA

Retrospective cohort (January 2000 – June 2011)

148 (n = 84 vs. n = 64)

Women with a singleton non-anomalous fetus with spontaneous preterm labour and intact membranes, between 20–23.9 week of gestation, and with cervical dilation ≥ 1 cm and effaced > 50 %.

Tocolytic medication

No treatment

Prolongation of pregnancy >7 days

(Database record of tocolytic treatment used i.e. magnesium sulfate, indomethacin or nifedipine, either used singly or in combination)

Perinatal death

Visintine 2008 [24]

USA

Retrospective cohort (1995–2006)

101 (n = 51 vs. n = 50)

Asymptomatic women followed from 14 weeks through 23 weeks 6 days gestation with a short cervical length, defined as <25 mm, placed with an ultrasound-indicated cerclage.

Indomethacin plus cerclage

Cerclage only

Prolongation of pregnancy >24, 32, or 35 weeks

(50 mg initially orally or rectally, followed by 25 mg orally every 6 h for about 48 h.)