Evaluating the Transvaginal Ultrasound Diagnostic Criteria for Abnormal First-Trimester Pregnancy With Follow-Up Into the Third Trimester and Validation of Results
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OBJECTIVE: To evaluate the current ultrasound diagnostic criteria for non-viable pregnancy in the first trimester. METHODS: We conducted a retrospective chart review involving 3 tertiary care institutions. Consecutive first-trimester ultrasound reports between January 2013 and June 2016 were reviewed. All first-trimester ultrasound examinations performed to assess pregnancy viability with adequate imaging or clinical follow-up were included. Inclusion criteria based on follow-up were adequate imaging to document ongoing intrauterine pregnancy or clinical follow-up demonstrating viability or non-viability. Data on mean sac diameter (MSD), yolk sac presence/diameter, embryo presence/length, presence of a heartbeat, and heart rate were collected. This was followed by a retrospective validation review of another consecutive cohort. RESULTS: Two hundred and forty-five examinations with a viable-pregnancy outcome and 301 examinations with a non-viable pregnancy outcome were reviewed. The main predictor of non-viable pregnancy was an MSD of ≥20 mm in the absence of a yolk sac (positive predictive value [PPV] 100%; 95% CI 93%-100%), embryo (PPV 100%; 95% CI 90%-100%), or heartbeat (PPV 100%; 95% CI 96%-100%]). Other predictors of non-viability were a measurable embryo without a yolk sac (PPV 100%; 95% CI 91%-100%), yolk sac diameter ≥8 mm (PPV 100%; 95% CI 91%-100%), and absence of heartbeat with an embryo ≥3 mm (PPV 100%; 95% CI 97%-100%). These findings were confirmed in a validation cohort of 45 viable and 53 non-viable pregnancies, with the exception of 1 case of viable pregnancy with no heartbeat and an embryo length 3.3 mm. Based on the median daily growth of 1.2 mm in the viable cohort, 21% of follow-up ultrasound examinations were performed too early for an MSD threshold of 20 mm and 55%, for an MSD threshold of 25 mm. CONCLUSION: In our cohort, MSD ≥20 mm in the absence of yolk sac or an embryo with heartbeat always predicted a non-viable pregnancy.
