Pregnancy-Specific β-1-Glycoprotein in First-Trimester Maternal Serum Is Influenced by Smoking

Abstract

Cigarette smoking influences the concentrations of certain markers in maternal serum during pregnancy. An approximate 20% reduction in pregnancy-associated plasma protein A has been noted in first-trimester maternal sera of smokers compared with nonsmokers. Furthermore, inhibin A is increased 40%–60% in maternal serum of second-trimester smokers. Adjustment for smoking with these 2 markers is important to reduce the false-positive rate in estimating the individual risk for Down syndrome. Pregnancy-specific β-1-glycoprotein (SP1)1 was first described 3 decades ago as pregnancy-associated plasma protein C (1) and Schwangerschafts protein 1(2). SP1 is synthesized by the syncytiotrophoblast and secreted into the maternal circulation, where the concentration increases continuously during pregnancy. The SP1 concentration in maternal serum is a marker of Down syndrome, with a reduced concentration noted early in the first trimester and an increased concentration in the second trimester (3)(4). Furthermore, serum SP1 is decreased in pregnancies with fetal growth restriction. Smoking has been reported to reduce the SP1 concentration in …