Ultrasound is an electronic technology, which uses the reflection of pulses of high frequency sound to produce an image. Ultrasound may be used in a variety of circumstances during pregnancy. It has been assumed that the routine use of ultrasound in early pregnancy will result in the earlier detection of problems and improved management of pregnancy complications when compared with selective use for specific indications such as after clinical complications (e.g. bleeding in early pregnancy), or where there are concerns about fetal growth.
The focus of this review is routine early pregnancy ultrasound (before 24 weeks). We have included 11 randomised controlled trials including 37,505 women. Early ultrasound improved the early detection of multiple pregnancies and improved gestational dating which may result in fewer inductions for post maturity. The detection of fetal malformation was addressed in detail in only two of the trials. There was no evidence of a significant difference between the screened and control groups for perinatal death. Results do not show that routine scans reduce adverse outcomes for babies or lead to less health service use by mothers and babies. Long-term follow up of children exposed to scans before birth did not indicate that scans have a detrimental effect on children's physical or intellectual development. Studies were carried out over three decades and technical advances in equipment, more widespread use of ultrasonography, and increased training and expertise of operators may have resulted in more effective sonography.