Randomized controlled trial of antenatal social support to prevent preterm birth

Abstract

Objective: To test the effect of a programme of additional antenatal social support on the occurrence of preterm birth (a birth from 20 to 36 weeks gestation) in women at risk of preterm birth.

Design: A prospective randomized controlled trial. The design was one of randomization before consent for a new treatment.

Setting: Three public hospital antenatal clinics in Perth and the offices of 87 obstetricians and general practitioners in Western Australia.

Subjects: 1970 pregnant women with poor obstetric histories entered the trial; 983 of these were randomly allocated to the programme group and 987 to the control group.

Interventions: Normal antenatal care was provided for both groups. In addition, members of the programme group were offered an intervention aimed at providing expressive (emotional) social support, consisting of antenatal home visits and telephone calls by midwives. Of the women allocated to the programme group, 24 refused consent and 69 were not traced before completion of their pregnancies, the remaining 890 women (90.5%) agreed to enter the programme, and each received at least one intervention.

Main outcome measures: Gestational age at completion of the pregnancy. A pregnancy ending before 20 weeks was labelled a miscarriage.

Results: There were 126/981 (12.8%) preterm births in the programme group and 147/986 (14.9%) in the control group. The outcome data for two women in the programme group and one in the control group could not be found. The unadjusted odds ratio for preterm birth in the programme was 0.84 (95% CI 0.65-1.09). The observed relative reduction in preterm births associated with the programme was 13.8% (95% CI -8.2% to +31.5%) and the trial had a 60% power to exclude a true relative reduction of 25%.

Conclusions: The results of this trial and those of other controlled clinical trials provide little evidence for the effectiveness of social support interventions in the prevention of preterm birth in women with poor obstetric histories.