Detection of fetal cardiac activity between 41 and 43 days of gestation.

Using a high-resolution real-time arc sector scanner, fetal cardiac activity was detected in ten normal intrauterine pregnancies, including one triplet gestation, between 41 and 43 days of gestation. Fetal heart rates ranged from 96 to 120 beats/min (mean 110) and were detected contiguous with the yolk sac as a tiny blinking, flashing, and/or rocking echo with a regular rhythm. The mean gestational sac fluid diameters ranged from 8 to 16 mm and the crown-rump lengths, when measurable, were less than 4 mm. The demonstration of early fetal cardiac activity in utero reduces parental anxiety and indicates a favorable prognosis in patients with threatened abortion, and virtually excludes the diagnosis of ectopic pregnancy.