Spontaneous abortion and pregnancy outcome after normal first-trimester ultrasound examination.

The aim of the study was to assess the spontaneous abortion rate and pregnancy outcome in a population of women with a normal first-trimester ultrasound examination. Gestational age or bleeding was the indication for 90% of the ultrasound scans. The spontaneous abortion rate increased with advancing maternal age. Other factors affecting the rate were indication for the scan and gestational age at the time of the scan. In the overall group, disregarding maternal age, the spontaneous abortion rate was 2.3%. This background rate of spontaneous abortion can be used to assess the added risk of chorionic villus sampling or other first- or second-trimester procedures. The incidence of antepartum and intrapartum complications in these pregnancies corresponded well with published figures.