Risk Factors Are Not Very Risky Once a Normal Embryonic Heart Rate is Seen in Early Pregnancy.

Objectives: To assess first-trimester prognosis when an early pregnancy sonogram demonstrates a normal embryonic heart rate and to determine how a number of risk factors affect prognosis.

Methods: Our study population consisted of 6597 first-trimester scans with gestational age (GA) ≤ 7.0 weeks (all with crown-rump length [CRL] <10 mm), normal embryonic heart, and known first-trimester outcome. We recorded GA; CRL; heart rate; first-trimester outcome; maternal age; presence, absence, and size of subchorionic hematoma; presence or absence of vaginal bleeding; and presence, absence, and size of uterine fibroids. We assessed first-trimester outcome in the study population and subsets based on the above data.

Results: First-trimester outcome was successful in 6030 of the 6597 cases (91.4%). The prognosis was somewhat worse with each of the following risk factors: maternal age ≥35 years, large subchorionic hematoma, and large or multiple uterine fibroids (P < .02, chi-squared or Cochran's test for trend, for all of these items). The rate of successful outcome was in the range of 83-88% with each of these risk factors and 93.8% in the absence of any of these factors.

Conclusions: The presence of a normal embryonic heart rate on an early first-trimester sonogram is a reassuring finding, indicating a likelihood of good first-trimester outcome of at least 83% even in the presence of risk factors, and of over 90% in the absence of such factors.