Pregnancy outcome among non‐participants in a trial on ultrasound screening

Abstract Our objective was to characterize and evaluate pregnancy outcome in women who declined participation in a trial on ultrasound screening in the second trimester. Between 1985 and 1987, 8768 women were recruited for a trial on ultrasound screening. By randomization, 4997 women were assigned to either a screening or a non‐screening group. Of the 1414 excluded women, data were retrieved from 1211 (86%). Participation was declined by 526 of these 1211 women, either because of anxiety regarding harmful effects of ultrasound or because they could see no benefits of ultrasound scanning. Non‐participants and participants were compared. The non‐participants were older, had a higher birth/pregnancy ratio, were less often smokers, and had fewer ultrasound examinations than the participants. There was a longer mean pregnancy length, an increased number of post‐term deliveries, more suspicions of small‐for‐gestational‐age fetuses and later detections of multiple pregnancies among non‐participants as compared with the screening group. No differences in neonatal morbidity were found except for a greater number of mild respiratory disorders in the non‐participant group. The non‐participant women were more obstetrically experienced and showed indications of a healthier lifestyle in comparison with participants. The differences found in pregnancy outcome could be explained by the ultrasound screening procedure. There were no major differences in neonatal morbidity between the groups. Copyright © 1998 International Society of Ultrasound in Obstetrics and Gynecology