Kopelman 1989.

Methods	RCT. Randomisation from a random number table via sealed envelopes. Blinding: not stated. Losses to follow‐up: 22 women out of 113 (19.4%) were excluded after randomisation; 6 of these were for non‐compliance.
Participants	113 women who met the following inclusion criteria: singleton pregnancy; gestational age 20‐35 weeks; irregular uterine contractions with clear evidence of cervical dilatation and effacement; persistent, regular uterine contractions (min frequency 8/hr) with or without cervical change. Exclusion criteria: known lethal fetal anomalies, chorioamnionitis, advanced cervical effacement and dilation (completely effaced and > 5 cm dilated).
Interventions	Parenteral tocolysis was given to all women (subcutaneous terbutaline and intravenous ritodrine) then women were randomly assigned to maintenance therapy with oral terbutaline (begun at 2.5 mg every 2 hours for 24 hours, then adjusted to 5 mg every 4 hours) or ritodrine (begun at 10 mg every 2 hours for 24 hours then adjusted to 20 mg every 4 hours). Terbutaline = 30 mg/day, ritodrine = 120 mg/ day.
Outcomes	Mean birthweight, perinatal deaths, hyperbilirubinaemia, tachycardia, tachypnoea, nausea/vomiting, antenatal readmission.
Notes	1 woman in each group was switched to the alternate drug because of intolerable side effects. In addition, there were 6 noncompliant women ‐ 4 from the ritodrine group and 2 from the terbutaline group. 2 of the 6 women chose to give birth elsewhere and the remaining 4 elected not to continue their medication because of side effects.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random number table.
Allocation concealment (selection bias)	Low risk	Sealed envelopes.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not stated.
Incomplete outcome data (attrition bias) All outcomes	Low risk	19% loss to follow‐up.
Selective reporting (reporting bias)	Unclear risk	Unable to assess.
Other bias	Low risk