Ultrasound and human-placental-lactogen screening early detection of twin pregnancies.

In the past five years gradual introduction of ultrasonic screening of pregnant women increased the ante-partum detection of multiple pregnancy from 60% in 1971 to 95% in the first half of 1975. At the same time the average gestational age for dection of multiple pregnancies diminished from thirty-three to twenty-five weeks. The corresponding figures for 1963 were 32% and thirty-six weeks. Plasma human-placental-lactogen concentrations were assessed for their value in selecting a smaller target group for subsequent ultrasonic screening. All but 2 of 39 twin pregnancies examined by single H.P.L. determinations had H.P.L. values more than 1 S.D. above the mean of the normal distribution. The use of plasma-H.P.L. screening might lower the proportion of patients requiring ultrasonography for antepartum diagnosis of multiple pregnancies to 16% of the total pregnant population.