[The incidence of abortions of viable pregnancies in the first trimester].

The spontaneous abortion rate in singleton pregnancies with sonographically proven heart activity between 5 and 13 weeks was analysed. Up to 15 weeks 8.6% of 395 patients miscarried. The abortion rate was higher in pregnancies with a gestational age < 9 weeks (12.5%), a maternal age > or = 35 years (15.5%) and vaginal bleeding (16.3%). The correlation of the abortion rate with these factors has to be taken into account when the prognosis of an individual gestation or the risk of invasive procedures is determined.