Pregnancy-specific beta-1 glycoprotein (SP-1) in normal and abnormal pregnancy.

Maternal serum levels of a pregnancy specific beta-1 glycoprotein (SP-1) were measured by radial-immunodiffusion in 369 normal pregnancies. Mean levels rose progressively to approximately 200 mg/l at 36 weeks of gestation followed by a plateau and a fall at term. The 95% confidence limits were established for SP-1 logarithmic correction of the positively skewed raw data and certain theoretical and practical advantages were demonstrated in the use of SP-1 compared with human placental lactogen (HPL) measurement in the assessment of fetal-placental growth and function. In a preliminary study of abnormal pregnancy states it was found that maternal serum SP-1 assay may aid in the early detection of retarded intrauterine growth, and that it provides a better monitoring system than HPL in this condition. SP-1 levles were normal in pregnancies complicated by hypertension without retarded intrauterine growth.