Ultrasound screening and perinatal mortality: controlled trial of systematic one-stage screening in pregnancy

In the hope of reducing perinatal risks associated with retardation of intrauterine growth a previously described two stage ultrasound screening schedule was evaluated by a controlled trial in 877 women with low risk single pregnancies. The two stages of ultrasound examination were an assessment of gestational age during early pregnancy followed by measurement of length from crown to rump and area of trunk at between 34 and 36 weeks' gestation. The product of crown to rump length and trunk area was calculated. The sensitivity of this schedule in identifying in advance 94% of babies who were small for dates at birth, with 90% specificity, and the speed and simplicity of measurement confirmed the accuracy and feasibility of two stage ultrasonography as a screening procedure. The controlled trial did not, however, show any benefit from its routine application in these low risk pregnancies. Show more

4997 of 7354 pregnant women had no clinical indication for an elective ultrasound examination at 12 weeks' gestation. 2482 of these women were randomly selected for ultrasound screening at 15 weeks and the remainder received the same standard antenatal care without the scan. Labour was less often induced among screened women both for all reasons (5.9% vs 9.1%, p less than 0.0001) and for suspected post-term pregnancy (1.7% vs 3.7%, p less than 0.0001). Earlier detection of twins had no effect on neonatal outcome. Among babies born to screened women, fewer were of birthweight less than 2500 g (59 vs 95, p = 0.005) and mean birthweight was 42 g higher (p 0.008). For babies born to screened women who smoked it was 75 g higher (p 0.012) and for those of non-smokers 26 g (not significant). The reason for the differences in mean birthweight could be that screened women reduced smoking in response to watching their fetus on the scan. Show more