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.
Early ultrasound improves the early detection of multiple pregnancies and improved gestational dating may result in fewer inductions for post maturity. Caution needs to be exercised in interpreting the results of aspects of this review in view of the fact that there is considerable variability in both the timing and the number of scans women received.
Diagnostic ultrasound is a sophisticated electronic technology, which utilises pulses of high frequency sound to produce an image. Diagnostic ultrasound examination may be employed in a variety of specific circumstances during pregnancy such as after clinical complications, or where there are concerns about fetal growth. Because adverse outcomes may also occur in pregnancies without clear risk factors, assumptions have been made that routine ultrasound in all pregnancies will prove beneficial by enabling earlier detection and improved management of pregnancy complications. Routine screening may be planned for early pregnancy, late gestation, or both. The focus of this review is routine early pregnancy ultrasound.
To assess whether routine early pregnancy ultrasound for fetal assessment (i.e. its use as a screening technique) influences the diagnosis of fetal malformations, multiple pregnancies, the rate of clinical interventions, and the incidence of adverse fetal outcome when compared with the selective use of early pregnancy ultrasound (for specific indications).
We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (September 2009).
Published, unpublished, and ongoing randomised controlled trials that compared outcomes in women who experienced routine versus selective early pregnancy ultrasound (i.e. less than 24 weeks' gestation). We have included quasi-randomised trials.
Two review authors independently extracted data for each included study. We used the Review Manager software to enter and analyse data.
Routine/revealed ultrasound versus selective ultrasound/concealed: 11 trials including 37505 women. Ultrasound for fetal assessment in early pregnancy reduces the failure to detect multiple pregnancy by 24 weeks' gestation (risk ratio (RR) 0.07, 95% confidence interval (CI) 0.03 to 0.17). Routine scan is associated with a reduction in inductions of labour for 'post term' pregnancy (RR 0.59, 95% CI 0.42 to 0.83). Routine scans do not seem to be associated with reductions in adverse outcomes for babies or in health service use by mothers and babies. Long-term follow up of children exposed to scan in utero does not indicate that scans have a detrimental effect on children's physical or cognitive development.