A randomized study of fetal abdominal diameter and fetal weight estimation for detection of light-for-gestation infants in low-risk pregnancies.

A total of 2771 pregnant women with gestational age estimated by ultrasound measurement of the fetal biparietal diameter (BPD) before the 22nd week of gestation were re-examined by ultrasound in the 32nd and 37th week of pregnancy at which time the fetal BPD and abdominal diameter (AD) were measured. An additional examination was performed at 34 weeks if the fetal weight in the 32nd week was estimated to be less than 95% of the expected mean weight. Light-for-gestational age (LGA) was suspected if the estimated birth-weight was less than 85% of the expected mean birthweight. This applied to 186 uncomplicated pregnancies in which there was no clinical suspicion of poor intrauterine growth. These pregnancies were randomly allocated to a treatment group (AD and estimated weight reported) or to a control group (AD and estimated weight withheld). Induction of labour was significantly more common in the treatment group (41%) than in the control group (15%). No statistically significant difference was found in the use of instrumental vaginal delivery or caesarean section. There was a suggestion of marginal benefit in terms of neonatal morbidity but this was not statistically significant.