Pregnancy specific beta1-glycoprotein (PSbetaG) has been identified in vitro in trophoblast cultures and in vivo, using transmission electron microscopy, in the syncytiotrophoblast, PSbetaG may, like other pregnancy proteins, have immunosuppressive properties.

Summary Maternal plasma levels of the trophoblast product, pregnancy‐specific β1‐glycoprotein (PSβG), have been measured both in normal pregnancies and in pregnancies complicated by pre‐eclampsia and/or fetal growth retardation. PSβG levels correlate significantly with placental and fetal weight and fall below the normal range in about 60 per cent of all patients with fetal growth retardation. PSβG measurements appear to give a considerably better indication of fetal size than measurements of either human placental lactogen (HPL) or plasma oestriol.

Summary Pregnancy‐specific β1–glycoprotein (PSβG) is a major product of the trophoblast which has only recently been identified. Like human placental lactogen, the concentration of PSβG in maternal blood rises throughout pregnancy until about 34 weeks, thereafter tending to remain constant until term, with only a small day‐to‐day variation in individuals. The circulating maternal levels of PSβG between 34 weeks and term are about 200 μg/ml, 20 to 30 times greater than the levels of placental lactogen, thus allowing detection and measurement of PSβG by relatively simple techniques. The levels of PSβG are above the normal range in the majority of twin pregnancies. It is suggested that PSβG measurements may be useful in assessing placental function and may help in the detection of multiple pregnancies at an early stage of gestation.

Summary The plasma concentrations of four ‘pregnancy proteins' and three steroid hormones have been measured throughout pregnancy in 15 primigravidae. Two of the proteins, human placental lactogen (HPL) and pregnancy‐specific β1‐glycoprotein (PS βG), are specific for pregnancy and correlate well with the stage of gestation. It is suggested that measurement of PSβG may be useful in assessing feto‐placental wellbeing. Neither of the pregnancy‐associated proteins, steroid‐binding β‐globulin (SB βG) and pregnancy‐associated α2‐glycoprotein (α2‐PAG), correlated with the length of gestation although, near term, plasma α2‐PAG levels appeared to be related to fetal weight. In addition, no correlation has been demonstrated between placental or fetal weight and any of the pregnancy‐specific proteins or steroid hormones studied.