Subchorionic Hematoma: Correlation of Grading Techniques With First-Trimester Pregnancy Outcome

To evaluate and compare grading systems of subchorionic hematoma (SCH) on first-trimester ultrasound examinations with live embryos to assess which best correlates with early pregnancy outcome and to assess the effect of gestational age at the time of diagnosis on outcome.

First-trimester live singleton pregnancies between 6 and 11 weeks' gestational age with SCH were identified by an institutional database search. First-trimester outcome was categorized as "live" or "demise" based on ultrasound or medical record documentation. Hematomas were categorized in 4 ways: (1) subjective (small, moderate, or large); (2) subjective size based on fraction comparison with gestational sac size; (3) subjective grading based on the estimated percentage of the gestational sac surrounded by hematoma; and (4) 3 orthogonal measurements of the hematoma.

A total of 434 sonograms met study inclusion criteria. The overall rate of first-trimester pregnancy failure was 12.0%. The rate of demise was significantly higher for hematomas diagnosed at or before 7 weeks (19.6%) than for those after 8 weeks (3.6%; P < .001). The size of the hematoma estimated as a fraction of gestational sac size significantly correlated with first-trimester pregnancy loss (P < .001). There was no statistical significance between first-trimester outcome and the other 2 subjective grading methods. Volume-based measurements provided spurious results because of the irregular shape of most hematomas.

Subjective hematoma size based on the fraction of gestational sac size correlates best with first-trimester pregnancy outcome. The earlier in pregnancy an SCH is detected, the higher the rate of subsequent pregnancy failure.