Prediction of abortion using three-dimensional ultrasound volumetry of the gestational sac and the amniotic sac in threatened abortion.

PURPOSE

To determine whether gestational sac volume (GSV) or amniotic sac volume (ASV) and/or the difference between them can predict abortion in women with first-trimester threatened abortion.

METHODS

Ninety patients between 6 and 12 weeks of gestation presenting with vaginal bleeding were studied. Seventy-six delivered after 24 weeks of gestation (group A) and 14 aborted before 20 weeks of gestation (group B). All patients had a singleton viable pregnancy demonstrated by transvaginal ultrasound. Gestational sac and amniotic sac volumes were measured in all the patients using three-dimensional transvaginal ultrasound with Virtual Organ Computer-aided Analysis software, and the gestational sac volume - amniotic sac volume (GSV - ASV) was calculated.

RESULTS

The groups did not differ in terms of age, parity, number of previous abortions, or term deliveries. The GSV (group A: mean 32.0 ± 27.7 cm(3) ; group B: 26.7 ± 29.1 cm(3) ) and the ASV (group A: 21.1 ± 25.5 cm(3) ; group B: 20.6 ± 26.0 cm(3) ) were not statistically different, while the GSV - ASV was significantly smaller in group B (aborting before week 20) (group A: 10.9 ± 10.9 cm(3) ; group B: 6.1 ± 8.6 cm(3) ; p < 0.05). Using receiver operator curves, the area under the curve for predicting normal pregnancy outcome of the GSV - ASV measurement was 0.654. When the GSV - ASV was 1.8 cm(3) or less, abortion was predicted with 84% sensitivity and 43% specificity.

CONCLUSIONS

The measurement of the GSV and the ASV are not good predictors of abortion in patients with first-trimester vaginal bleeding, whereas the use of the GSV - ASV may be helpful in predicting the outcome of pregnancy.