Predictive value of presence of amniotic sac without visible embryonic heartbeat in diagnosis of early embryonic demise.

OBJECTIVES

To assess the diagnostic value and impact on management of visualizing on ultrasound an amniotic sac without a live embryo (amniotic sac sign). We also examined the potential effect on the number of follow-up visits in early pregnancy units of incorporating this sign into current diagnostic algorithms.

METHODS

This was a prospective cohort study of all pregnant women who attended a single specialist early pregnancy unit from July 2017 to November 2018 with symptoms of pain and/or bleeding, or with a history of ectopic pregnancy or miscarriage, at < 14 weeks' gestation. Detailed initial ultrasound findings were documented, including whether an amniotic sac was present in a normally sited intrauterine pregnancy with absence of a live embryo. Women were followed up until a conclusive diagnosis was made.

RESULTS

The study included 6012 women who attended our unit with early pregnancy complications during the study period. A conclusive diagnosis was reached on the initial scan in 4221 (70.2%), whilst 1135 (18.9%) women had a pregnancy of uncertain viability and 656 (10.9%) had a pregnancy of unknown location (PUL). All women with a pregnancy of uncertain viability required follow-up ultrasound scans to differentiate between a live pregnancy and early embryonic demise. An amniotic sac in the absence of a live embryo was found in 174/1135 (15.3%) women with a pregnancy of uncertain viability at the initial ultrasound scan. The diagnosis of early embryonic demise was confirmed in all 134 of these women who attended their follow-up scans. The presence of an amniotic sac without a live embryo at the initial visit had a specificity of 100% (95% CI, 98.53-100.00%) and positive predictive value of 100% (95% CI, 97.2-100.0%) for the diagnosis of early pregnancy failure. A total of 1403/6012 (23.3%) women were asked to attend for a follow-up ultrasound scan to resolve diagnostic uncertainties, including 268/656 (40.9%) women with a PUL. The majority of follow-up scans needed to reach a conclusive diagnosis were in women with a pregnancy of uncertain viability (1135/1403 (80.9%)). By using the presence of the amniotic sac sign to diagnose early pregnancy failure at the first visit, the number of follow-up scans for pregnancies of uncertain viability would be reduced by 14.4%, which accounted for 11% of all follow-up scans during the study period.

CONCLUSIONS

The finding on ultrasound of an amniotic sac without a live embryo (amniotic sac sign) is a reliable marker of early pregnancy failure and could reduce the number of follow-up scans by 11% in cases of diagnostic uncertainty. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.