ABSTRACT
The incidence of spontaneous abortion once embryonic development has reached the stage
of sonographically demonstrable cardiac activity has not been precisely determined
in a large population. This retrospective study was designed to determine the risk
of pregnancy loss after first trimester sonographic confirmation of fetal cardiac
activity. A total of 840 patients were referred for ultrasound examination to the
Perinatal Center, University of Cincinnati, between January 1, 1979 and December 31,1985
who fulfilled the criteria of singleton pregnancy with sonographically visible fetal
cardiac activity and crown-rump length consistent with gestational age ≤ 12 weeks.
Patients were grouped into two categories based on the absence (control) or presence
of vaginal bleeding (bleeding) prior to or at the time of the ultrasound examination.
The abortion rates for the two groups were 5.2 and 16.4%, respectively (P < 0.001). The relative risk of abortion in patients with vaginal bleeding was nearly
four-fold greater than the control population. In the control group there was a significantly
greater incidence of pregnancy loss in the ≥34 years age group compared to <34 years
age patients (4.4 versus 11.1%, P < 0.05). Although there was no significant effect of race on abortion rates, low
socioeconomic status almost doubled the relative risk of miscarriage. We conclude
that the presence of visible fetal cardiac activity in the first trimester predicts
a decreased risk for spontaneous abortion compared to generally reported rates. The
significant risk factors for increased chance of abortion are vaginal bleeding, advanced
maternal age, and low socio-economic status.
