To determine if regular weight measurement throughout pregnancy can reduce excessive gestational weight gain.

A randomised controlled trial.

A tertiary obstetric hospital in Melbourne, between July 2007 and May 2008.

236 pregnant women recruited at ≤ 14 weeks’ gestation.

Women allocated to the intervention group were given a personalised weight measurement card, advised of their optimal gestational weight gain (based on their body mass index at the time of recruitment and the United States Institute of Medicine guidelines), and instructed to record their weight at 16, 20, 24, 28, 30, 32 and 34 weeks’ gestation. The control group were weighed at recruitment, but were not given instructions about regular weight measurement. All participants were blinded to the purpose of the study.

Weight gain from recruitment to follow-up at 36 weeks’ gestation.

In the study population, there was a trend to less weight gain in the intervention group. The women in the intervention group experienced a mean (SD) per-week weight gain of 0.44 (0.173) kg compared with those in the control group, who gained 0.46 (0.156) kg/week (mean difference, 0.02 kg/week; 95% CI, − 0.02 to 0.07 kg/week). The intervention significantly reduced gestational weight gain in the group of women who were overweight but not obese at recruitment: those in the intervention group (20 women) gained a mean (SD) of 0.42 (0.153) kg/week and the control group (18 women) gained 0.54 (0.123) kg/week (mean difference, 0.12 kg/week; 95% CI, 0.03 to 0.22 kg/week; P = 0.01).

Regular weight measurement in pregnancy was not found to be effective in reducing weight gain, except among women who were overweight but not obese before pregnancy.

Australian Clinical Trials Registry ACTRN12607000272493