Objectives: (1) To study the predictors of pregnancy continuation up to 28 weeks in first-trimester threatened miscarriage after a single clinical and ultrasound (US) evaluation. (2) To assess the role of both clinical and US predictors in counseling and decreasing repeated emergency follow-up scans.
Methods: A prospective observational study that included a cohort of 241 patients with threatened miscarriage (≥6-12 weeks) was conducted. They had a single clinical and US evaluation, and then they were contacted by weekly phone calls until completing 28 weeks' gestation or reporting miscarriage. Independently, all patients were followed by the recommended routine US scanning with or without emergency visits.
Results: Two hundred thirty-three patients completed the study, of whom 193 patients continued up to 28 weeks' gestation, and 40 miscarried (17.1%). Only spotting/mild bleeding episodes and progesterone treatment were the clinical predictors of fetal viability. The embryonic/fetal heart rate (E/FHR) was the best single US predictor, with a specificity and positive predictive value of 95.3% and 97.2%, respectively. Combining 3 US parameters, at their best cutoff points (E/FHR >113 beats per minute, crown-rump length >19.9 mm, and gestational sac diameter >27.3 mm), had a specificity and positive predictive value of 98% and 99% (first-trimester US triad of fetal viability).
Conclusions:  In first-trimester threatened miscarriage, clinical parameters that could predict fetal viability included spotting/ mild bleeding and progesterone treatment.  After a single US scan, the presence of at least an E/FHR of greater than 113 bpm or the suggested first-trimester US triad appeared as a simple, measurable, and effective predictor of pregnancy continuation up to 28 weeks.  These US predictors are not to replace the recommended scheduled scanning during pregnancy.  This can improve patients' counseling and decrease the need for repeated emergency follow-up scans. Otherwise, there is an indication for repeating US scans at a 1-week to 10-day interval.
Keywords: clinical predictors; fetal viability; first-trimester miscarriage; ultrasound predictors.
© 2020 by the American Institute of Ultrasound in Medicine.