Diagnosis of viability in early pregnancy with vaginal sonography

The detection rate of embryonic heart action using vaginal sonography was evaluated in 363 normal singleton pregnancies in the first trimester. Visible cardiac activity was present at the earliest at a gestational age of 40 days; in addition, the smallest chorionic cavity had a mean diameter of 9.3 mm, the lowest human chorionic gonadotropin (beta-hCG) concentration (calibrated against the first international reference preparation) measured 6,770 mIU/mL, the thinnest trophoblast was 1 mm, and the shortest crown-rump length was 2 mm. Cardiac pulsations were identified in all cases either at a menstrual age greater than or equal to 46 days, a beta-hCG greater than or equal to 47,171 mIU/mL, a mean chorionic cavity diameter greater than or equal to 18.3 mm, or a trophoblast thickness greater than or equal to 5 mm. The heart rate (mean +/- SD) increased from 110 +/- 8 beats per minute (bpm) at 5 weeks menstrual age to 170 +/- 6 bpm at 9 weeks and declined thereafter to 159 +/- 3 bpm at 13 weeks. Vaginal sonography enables a rapid and reliable assessment of embryonic life in early pregnancy.