Circulating levels of pregnancy specific beta 1 glycoprotein in late pregnancy: nyctohemeral and day-to-day variation, and variation during labour.

Circulating levels of pregnancy-specific beta 1 glycoprotein have been determined in a number of physiological situations in late pregnancy. The apparent variation in five subjects studied over a 24-hour period was not in excess of that due to the assay. Excess variation was apparent in 2 of 11 subjects studied daily for up to 8 days, and in 6 of 16 patients studied serially during labour.