Controlled trial of ultrasound screening for light for gestational age (LGA) infants in late pregnancy.

The study included 3311 pregnant women: 1570 in the screened group and 1741 in the unscreened group. In the screened group, ultrasound was offered routinely in the 32nd and 37th week of pregnancy, at which time the fetal biparietal diameter (BPD) and the abdominal mean diameter (AD) were measured. If, after the first ultrasound examination, the estimated weight was less than 85% of the expected mean birthweight, a finding of light for gestational age (LGA) was suspected and the ultrasound examination was repeated in the 34th week. In the screened group 6.5% of the women were at risk at the final ultrasound examination (the sensitivity was 38%) and the predictive values of abnormal and normal weight deviation were 60% and 93%, with a specificity of 97% and a relative risk of 9. Ultrasound was offered to the unscreened group only in cases of clinical concern (23% of the women). In the unscreened group 34% of the 158 LGA infants had ultrasound performed before delivery because of clinical concern. By including pregnancies induced before ultrasound could be performed, 45% of the LGA infants in the unscreened group were suspected before delivery. No significant difference between the rate of induction, instrumental deliveries and caesarean sections was found between the two groups. No benefit in terms of decreased incidence of infants with low Apgar score and acidosis was achieved.