Kok 2008.

Methods	Multi‐centre RCT.
Participants	Inclusion criteria: term singleton, breech presentation pregnancies. GA of 36 weeks onwards. N = 320. Exclusion criteria: maternal exclusion: any contradiction to labour or vaginal birth, scarred uterus other than transverse in the lower segment, known uterine anomalies, placental abruption in the obstetric history, preeclampsia, maternal cardiac disease, third‐trimester bleeding. Fetal exclusion: IUGR (EFW < 5th percentile for GA assessed by ultrasonography), fetal anomalies or an extended fetal head, oligohydramnios (defined as an AFI ≤ 5 cm) and non‐reassuring signs of fetal well‐being.
Interventions	Intervention: tocolytic: nifedipine ‐ calcium channel blocker (A2) ‐ oral. Nifedipine (2 doses of 10 mg) orally. N = 160 but 154 analysed. Comparison:placebo: placebo capsules. N = 160 but 156 analysed.
Outcomes	Primary: successful ECV defined as a fetus in cephalic position 30 minutes after the ECV procedure. Secondary: fetal presentation at birth, mode of birth and adverse maternal (major side effects due to medication, hypotension with fetal consequences, anaphylactic shock due to the medication and any adverse cardiac events due to medication intake) and fetal events (fetal death, emergency delivery, fetal bradycardia, premature rupture of the membranes and placental abruption within 24 hours after the ECV procedure). Minor side effects: nausea, dizziness and flushing and cessation of treatment because of side effects.
Notes	Nifedipine group ‐ 2 women excluded as they were less than 39 weeks' gestation, 2 excluded as they were repeat versions, 2 women lost to follow‐up. Placebo group ‐ 2 women excluded as they were less than 38 weeks, 2 excluded as they were repeat versions. Study reports no events for fetal death; emergency delivery less than 24 hours; placental abruption less than 24 hours; premature rupture of membranes less than 24 hours; maternal hypotension with fetal consequences; anaphylactic shock.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer blocks of 10, stratified for centre and parity.
Allocation concealment (selection bias)	Low risk	Pharmacy prepared sealed opaque containers with study medication and kept an allocation list until completion of the study.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blinded. All participants, nurses and doctors who performed the ECV were blinded to the assignment.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Double‐blinded. All participants, nurses and doctors who performed the ECV were blinded to the assignment.
Incomplete outcome data (attrition bias) All outcomes	Low risk	6 women were lost to follow‐up or were excluded in the nifedipine group, and 4 women in the control group.
Selective reporting (reporting bias)	Unclear risk	We did not assess the trial protocol.
Other bias	Unclear risk	Baseline characteristics were similar. Baseline characteristics (Table 1) indicate generally good balance, although there appears to be some imbalance in placental anterior localisation (44 vs 55). Some imbalances were seen in some of the ethnicity data (Central African (4 vs 10) and Other (18 vs 9).