Methods	Randomised controlled trial of routine antepartum care versus a preterm labour detection clinic in which women were seen on a weekly or biweekly basis, the cervix examined at each visit and education provided regarding subtle signs of labour
Participants	All women were from the obstetric clinic of the University of Pennsylvania Hospital, USA. 376 black women considered at high risk for preterm birth based on a Papiernik-Creasey Scoring system value of 10 or more (Creasy 1980). 178 control patients and 198 women assigned to preterm labour detection clinic
Interventions	Attendance at a preterm labour detection clinic on a weekly or biweekly basis from 22 weeks’ gestation. Cervical assessment by 1 of 3 physicians at each visit. Education provided by a nurse specialist regarding subtle signs of labour
Outcomes	Gestational age at delivery, birthweight, preterm PROM, inpatient costs, outpatient costs
Notes	Higher rate of accrual into the intervention group due to: (1) high-risk women who participated in the Preterm Labour Detection Clinic in earlier pregnancies being uniformly assigned to it in subsequent pregnancy; (2) higher elective abortion and transfer of care rates in control group
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Consecutive numbers of a random numbers table were used to allocate the first 479 participants whilst the second sample of 464 women was divided into groups by birthday (even versus odd day of the month)
Allocation concealment (selection bias)	High risk	Date of birth used for allocation of half of participants.
Blinding (performance bias and detection bias) All outcomes	Low risk	Neither the physicians or the control patients were made aware they were at high risk of preterm birth. Not possible to blind participants attending the preterm labour detection clinic due to the frequency of attendance
Incomplete outcome data (attrition bias) All outcomes	High risk	Insufficient reporting of attrition/exclusions: there were missing data (approximately 20%) for neonatal outcomes as not all infant case notes were examined
Selective reporting (reporting bias)	Unclear risk	Insufficient information about the sequence generation process to permit judgement of risk of bias
Other bias	Unclear risk	Women included in study during more than one pregnancy.