A pilot scheme was introduced in Manchester to provide additional social support to pregnant women at above average risk of giving birth to a low-birthweight baby. The help of lay workers, known as family workers, was made available to eligible women. The effect on infant birthweight of offering the help of a family worker was assessed by a randomized controlled trial. No significant differences were observed between the experimental and control group, but on a number of grounds the interpretation of this finding is not straightforward, and further research is recommended.