Radioimmunoassay of serum SP 1 and HPL in normal and abnormal pregnancies.

Serum concentrations of the pregnancy-specific beta 1-glycoprotein (SP 1) and human placental lactogen (HPL) were measured by radioimmunoassay in 372 blood samples obtained from 40 women in the second half of a normal singleton pregnancy. The mean level of SP 1 steadily increased from 40 micrograms/ml in the 22nd week of pregnancy to 168 micrograms/ml in the 36th week of gestation and thereafter reached a plateau. The half-life of SP 1 during the first week after delivery was about 39 h. The clinical value of SP 1 in comparison to HPL estimations was assessed in a prospective study of a few high risk pregnancies. There were no significant differences between serum SP 1 and HPL levels in pregnancies complicated by preeclampsia with or without intrauterine growth retardation and in twin pregnancies. Serum HPL and SP 1 levels were equally effective in predicting placental insufficiency with fetal growth retardation.