Observations on the dating of pregnancy.

The relationship between the concentrations of placental proteins and the stage of gestation has been examined. Human chorionic gonadotrophin and Schwangerschaftsprotein 1 were measured in two groups of patients: one a group of 13 women studied daily from conception to 21 days after ovulation and the other 43 normal pregnancies studied from 5 to 16 wk gestation. The results of assessment of the stage of gestation as determined by placental protein assay were compared with the dating obtained from last menstrual period and ultrasonic scan. The measurement of placental proteins was at least as accurate as the last menstrual period or ultrasonic scan in determining the stage of gestation.