What do placental function tests predict? Observations on placental lactogen levels in growth retardation and fetal distress.

Single blood samples were obtained from an unselected population of 527 women between 36 and 40 wk gestation. Serum placental lactogen levels were lower than normal in patients whose infants were growth retarded or developed fetal distress in labor. These associations were independent; the fetal distress group did not contain an excess of subjects with growth retardation. Thus, the results of a biochemical test reflect dynamic aspects of placental function and not simply the overall growth of fetus and placenta.