Diagnosis of Placental Function by Prediction Curves for Heat-Stable Alkaline Phosphatase (HSAP)

In order to establish an effective diagnostic method for placental function using HSAP, the authors formulated two expressions to predict HSAP values for their rise before 38.7 weeks of gestation and declining after that; logey=1.03a-3.37+0.123x (i), and y=Y(l+d/100) (ii), respectively. Further they prepared a chart of curves for these predicting expressions. The results obtained are as follows: (1) In normal pregnancies the deviation of prediction from measured values of HSAP was ±15% in 94% of the cases examined. (2) Many of cases of abnormal pregnancy showed a low level of HSAP, -15% or lower, and abnormal signs in HSAP pattern were found several days or weeks prior to the onset of fetal troubles. (3) Prolonged pregnancy with fetal troubles was able to be distinguished from “false” prolonged pregnancy. (4) In two consecutive pregnancies in the same woman, the courses of HSAP were strikingly consistent as far as both pregnancies were normal. The last fact suggests that the placental production of HSAP and its release into the maternal blood may be influenced by the individual constant a in expression (i). (5) It is recommended that the HSAP prediction curve is worthy to use as an easy screening method for placental function in the third trimester of pregnancy.