Subchorionic hematomas in early pregnancy: clinical outcome and blood flow patterns.

A case control study of 59 women with subchorionic hematomas compared to 135 normally pregnant. Transvaginal ultrasound was used to image the pregnancy, and identify the site and size of the hematomas. Color flow Doppler was used to calculate velocity indices of the spiral arteries. More spontaneous abortions occurred in women with subchorionic hematomas (SCH). There was general correlation between gestational age, velocity indices, and hematoma size. There were 10 spontaneous abortions in the study group (17%) versus 9 (6.5%) in the controls (P = 0.02). Hematoma size did not affect outcome, but site did. Most hematomas associated with abortion were found in the corpus or fundus of the uterus, not in the supracervical area (P = 0.03). The presence of a hematoma did not affect the frequency of preterm delivery. In conclusion, subchorionic hematomas in early pregnancy are associated with an increased risk of spontaneous abortion. Flow disturbances are seen in the spiral arteries, but these are probably secondary effects. The critical factor is site of hematoma, not volume.