Merkus 1978.

Methods	Design: randomised controlled trial (3 arms). Multicentre study: no (1 centre). International: 1 country, The Netherlands. Follow‐up period: 27 days. Per‐protocol analysis: no. Intention‐to‐treat analysis: yes.
Participants	N = enrolled and randomised pregnant women 18. Experimental group "A": n = 4 (NA‐872 at 100 mg(EG"A")). Control group "A": n = 4 (no treatment(CG"A")). Experimental group "B": n = 5 (NA‐872 at 200 mg (EG"B")) Control group "B" : n = 5 (no treatment (CG"B")) 18 participants completed study and analysed (9 women EG groups/9 women CG groups). 1.‐ Gestational age (days): EG group: 196 to 243 CG group: 196 to 243 2.‐ L/S ratio: EG"A" group: 1.52 (+/‐ 1.26) CG"A" group: 1.25 (+/‐ 1.40) EG"B" group: 1.07 (+/‐ 0.96) CG"B" group: 1.17 (+/‐ 1.58) 3.‐ Inclusion criteria: Pregnant women with a threatened premature delivery. 4.‐ Exclusion criteria: Women with ruptured membranes
Interventions	1a. Experimental group "A": (NA‐872) was given a daily infusion of 100 mg NA‐872 in 5% glucose. 1b. Experimental group "B": (NA‐872) was given a daily infusion of 200 mg NA‐872 in 5% glucose. 2a. Control group "A": (no treatment) was infused with a 5% glucose solution alone. 2b. Control group "B": (no treatment) was infused with a 5% glucose solution alone. Co‐intervention: Isoxsuprine (Duvadilan). Treatment duration: 5 days.
Outcomes	Primary: Estimation of L/S ratio of amniotic fluid obtained by amniocentesis (24 hours, 48 hours, 1 week, 2 weeks and 3 weeks after infusion.
Notes	1.‐ A priori sample size estimation: no. 2.‐ Sponsor: not reported. 3.‐ Role of sponsor: not reported. 4.‐ Conflict of interest: not reported. 5.‐ Number of clinical trial: not reported.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "in a double blind randomised study it was investigated whether NA‐872" (page 99). Comment: insufficient information to permit judgment of 'Low risk' or 'High risk'.
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient information to permit judgment of 'Low risk' or 'High risk'.
Blinding of participants and personnel (performance bias)	Unclear risk	Quote: "in a double blind study it was investigated whether NA‐872" (page 99). Comment: insufficient information to permit judgment of 'Low risk' or 'High risk'.
Blinding of outcome assessment (detection bias)	Low risk	Quote: "the amniotic fluid was determined with an automatic machine" (page 99). Comment: due to the way in which the samples were analysed by an automatic instrument, we thought it likely that they were blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: data for primary outcome available for 100% of the sample
Selective reporting (reporting bias)	Low risk	Comment: all the outcomes listed in the method section described in results.
Other bias	Low risk	Comment: no other potential source of bias.