First-trimester detection of amniotic sac in relation to miscarriage.

OBJECTIVES

The purposes of this study were to make clear the amniotic sac detection rate, and to determine whether the detection of an amniotic sac can effectively predict miscarriage in the first trimester.

STUDY DESIGN

This study included 169 normal pregnancy cases and 169 miscarriage cases. Both groups consisted of cases with a crown-rump length (CRL) of less than 40 mm.

RESULTS

In normal pregnancies, the amniotic sac was detectable at a CRL of 7 mm, or longer, and its detection rate varied proportionately with the length of the crown rump. In the miscarriage cases, the detection of an amniotic sac was possible at a CRL of less than 7 mm, and it was independent of the length of the crown rump. At a CRL of less than 7 mm, the amniotic sac was detected in 6 miscarriage cases, and the amniotic sac size increased after embryonic death in 19 miscarriage cases. The amniotic sac detection rate was 38% (65 cases) in all miscarriage cases.

CONCLUSION

Detection of an amniotic sac might be one of the useful signs indicating miscarriage when the CRL is less than 7 mm, at which point detection in normal cases is not yet possible.