Prediction of first-trimester outcome with ultrasound

Prediction of first-trimester outcome with ultrasound – Tips from Other Journals

Barbara Apgar

Vaginal bleeding affects up to 20 percent of first pregnancies and is the most common indication for first-trimester ultrasonography. Transvaginal ultrasonography has enabled the detection of blighted ovum and first-trimester fetal demise. Approximately 18 percent of women with vaginal bleeding in the first trimester will have ultrasonographic evidence of subchorionic hematoma. Bennett and associates performed a retrospective review to determine the significance of subchorionic hematoma size, gestational age and maternal age on pregnancy outcomes.

The review included 516 patients who presented with vaginal bleeding, a live fetus and a subchorionic hemorrhage in the first trimester. Hematoma size was determined by the percentage of the chorionic sac elevated by the hematoma.

The overall spontaneous abortion rate was 9.3 percent. The rate of spontaneous abortion differed little between pregnancies exhibiting a small separation and those with a moderate-size separation, but the rate nearly doubled when the separation was large. The spontaneous abortion rate was almost twice as high in women 35 years of age or older, compared with younger women, and was 2.3 times higher in women who presented with vaginal bleeding at eight weeks of gestational age or less.

Among women younger than 35 years of age, the spontaneous abortion rate was substantially higher in women with large hematomas detected on ultrasound than in women with small or medium-size hematomas in both gestational age categories. Patients with large hematomas at eight weeks of gestational age or less had a 20 percent spontaneous abortion rate, compared with an 8.2 percent rate and an 11 percent rate, respectively, for those with small and medium-size hematomas. The younger patients had a 3.6 to 4.8 percent loss rate if the hematoma was small or medium-size, compared with a rate of 9.1 percent if the hematoma was large.

Overall, younger women with subchorionic hematomas presenting with vaginal bleeding at a gestational age of eight weeks or less had a 10.5 percent rate of spontaneous abortion, whereas the rate was 5 percent if vaginal bleeding occurred at a gestational age greater than eight weeks. The overall spontaneous abortion rates were higher in women 35 years of age or older. The highest rate of spontaneous abortion occurred in the older women with large hematomas. Separation of the chorionic sac circumference by the hematoma of two-thirds or greater was a significant predictor of spontaneous abortion. A small or moderate-size separation did not significantly increase the rate of pregnancy loss. Because the patients in the study group were not compared with a control group, the increase in the relative risk of spontaneous abortions can only be assessed in this particular population.

The authors conclude that the results of this study support an increased rate of spontaneous abortion in women of advanced maternal age, women with a large subchorionic hematoma on ultrasonographic evaluation and women with bleeding at eight weeks of gestation or less. Recognition of a subchorionic hematoma on ultrasound may help the clinician counsel the patient about possible outcomes of the pregnancy.

Bennett GL, et al. Subchorionic hemorrhage in first-trimester pregnancies: prediction of pregnancy outcome with sonography. Radiology 1996;200:803-6.

COPYRIGHT 1997 American Academy of Family Physicians

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