Practical Screening for the Dysfunctional Feto-Placental Unit During Pregnancy

Abstract

It is well recognized that the purely clinical approach does not always detect every compromised fetus. Laboratory tests for placental function is now regarded as part and parcel of the antenatal care of the patient with high-risk pregnancy. The reliability of these tests as a screening procedure for risk pregnancy is fairly well established at present.
For example, the determination of estrogen (estriol) in maternal urine and hCS in maternal blood is clinically most useful. “Useful” in this sense, however, does not imply that they are intrinsically superior to other parameters, but merely implies that the technology is well established and that there is adequate published information regarding it. Therefore, the author has attempted to set up a practical guideline in screening the function of the feto-placental unit by measuring hCS with hemagglutination assay (HPL-HAR Test kit) and determining estriol by hemagglutination inhibition assay (E₃-HAIR Kit).
Urinary estriol levels were plotted on the vertical axis, and serum hCS was plotted on the horizontal axis. Low estriol and hCS zones were determined by drawing a line at the lowest limit of these hormones in normal pregnancy. The area on which the two zones were superimposed was designated an absolutely abnormal zone. Furthermore, dehydroepiandrosterone sulfate (DHAS) and oxytocin challenge tests were added for a dynamic test of placental function.
In early pregnancy, placental function was estimated by the measurements of hCG and hCS, the hormones produced by the placenta. hCG levels were plotted on the vertical axis, and hCS values were plotted on the horizontal axis of the monitoring table.
Summarized data are as follows :
In threatened abortion which terminated in fetal loss, “the point” moved to the lower left part on the “table”. On the other hand, in cases with favorable outcome, “the point” moved to the right. In molar pregnancy, the hormone pattern was 'high hCG' and 'low hCS' and was different from that in abortion. In cases of anencephalic, congenital enzymatic deficiency of the placenta, and Wharton's jelly defect of the umbilical cord, “the point” remained in the low estriol zone. With mild toxemia of pregnancy, “the point” also remained in the low estriol zone. With sensitized rhesus incompatibility, “the point” gradually moved to the low estriol zone. In cases of placental insufficiency and mild toxemia of pregnancy (hypertensive type), “the point” moved to the low hCS zone. In cases of chronic hypertension, retarded fetal growth, and aortic insufficiency, “the point” remained in the low hCS zone. With intrauterine fetal death, “the point” was always in the absolutely abnormal zone. With severe toxemia of pregnancy, “the point” moved into the absolutely abnormal zone. In cases of well-controlled diabetic disease or hyperthyroidism, and of rhesus incompatibility with low antibody titers, “the point” was in the normal zone.
In cases with “the point” present in the low estriol zone, the DHAS dynamic test should be done, and the reserve-function of the feto-placental unit should be evaluated. In cases with “the point” present in the low hCS zone, it is necessary to use the oxytocin challenge test to assess the reserve-function of the placenta.
In conclusion, the effective use of these methods is of value in predicting the dysfunction of the feto-placental unit, and it is hoped that the employment of these methods for the high risk foetus in the early stages might lead to more intensive obstetric care and might contribute to the reduction of perinatal loss.