Effects of repeated prenatal ultrasound examinations on childhood outcome up to 8 years of age: follow-up of a randomised controlled trial

Backgound Despite the widespread use of prenatal ultrasound studies, there are no published data from randomised controlled trials describing childhood outcomes that might be influenced by repeated ultrasound exposures. We previously undertook a randomised controlled trial to assess the effects of multiple studies on pregnancy and childhood outcomes and reported that those pregnancies allocated to receive multiple examinations had an unexplained and significant increase in the proportion of growth restricted newborns. Our aim was to investigate the possible effects of multiple prenatal ultrasound scans on growth and development in childhood. Here, we provide follow-up data of the childrens' development. Methods Physical and developmental assessments were done on children whose pregnant mothers had been allocated at random to a protocol of five studies of ultrasound imaging and umbilical artery Doppler flow velocity waveform between 18 and 38 weeks' gestation (intensive group n=1490) or a single imaging study at 18 weeks' gestation (regular group n=1477). We used generalised logistic and linear regression models to assess the group differences in developmental and growth outcomes over time. Primary data analysis was done by intention-to-treat. Findings Examinations were done at 1, 2, 3, 5, and 8 years of age on children born without congenital abnormalities and from singleton pregnancies (intensive group n=1362, regular group n=1352). The follow-up rate at 1 year was 85% (2310/2714) and at 8 years was 75% (2042/2714). By 1 year of age and thereafter, physical sizes were similar in the two groups. There were no significant differences indicating deleterious effects of multiple ultrasound studies at any age as measured by standard tests of childhood speech, language, behaviour, and neurological development. Interpretation Exposure to multiple prenatal ultrasound examinations from 18 weeks' gestation onwards might be associated with a small effect on fetal growth but is followed in childhood by growth and measures of developmental outcome similar to those in children who had received a single prenatal scan.