Pregnancy-associated plasma protein-A (PAPP-A) and hCG in early pregnancy

Pregnancy-associated plasma protein-A (PAPP-A) is a recently described glycoprotein of unknown biological function. The development of a radioimmunoassay enabled us to measure plasma levels of PAPP-A and human chorionic gonadotrophin (hCG) in 12 non-pregnant volunteers and in 159 women in early pregnancy attending the outpatient clinic for legal abortion. PAPP-A but not hCG was measurable in all non-pregnant women. In pregnant patients (with 36 to 86 days of amenorrhea) hCG reached a peak value (163.1-197.6 ng/ml) between the 9th and the 13th week whereas PAPP-A steadily increased throughout this period of pregnancy. Between the 6th and the 13th week after the last menstrual period, levels of PAPP-A increased proportionally more than hCG. This work provides the first evidence of a PAPP-A production in non-pregnant subjects and the very early marked increase of PAPP-A secretion during pregnancy.