Normal early pregnancy: serum hCG levels and vaginal ultrasonography findings.

Vaginal sonography and determination of serum hCG levels were carried out in 22 healthy pregnant women every 2 to 4 days after the first positive pregnancy test until a living fetus was observed. Gestational age was calculated from the day of ovulation, assessed by LH surge or hCG administration, plus 14 days. A gestational sac of 1-3 mm was detected at a mean (SEM) of 31.2 (0.2) days of gestation (range 30-33 days). The corresponding mean hCG level was 730 iu/l (30) and the range 467-935 iu/l (International Reference Preparation). The yolk sac was detected at a mean of 36.0 (0.2) days, range 34-38 days, at a mean hCG level of 4130 iu/l (370), range 1120-7280 iu/l. Fetal heart motion was visible at a mean of 41.1 (0.3) days, range 39-43 days and the corresponding mean hCG level was 12,050 iu/l (1240), range 5280-22,950, iu/l. The yolk sac and the fetal heart motion were always seen when the sac exceeded 10 and 18 mm in mean diameter, respectively.