To study the physiological functions of the human placenta, the histochemical determination of alkaline. phosphatase in the placenta as one of the enzymological studies was done. Forty placentas of normal pregnancy from the beginning to the overterm, and nineteen placentas of abnormal pregnancy-6 cases of the spontaneous abortion at relatively early stages including incomplete and missed abortion, 3 cases of the intrauterine fetal death, 5 cases of toxemia of pregnancy, 2 cases of placenta previa partialis, and 3 cases of chorionic tumors were taken at Iran-11 Hospital since March till October 1965.
In normal pregnancy, the activity of alkaline phosphatase in the placenta was gradually increased to its peak at the 6th month of pregnancy and maintained to the term.
The brush border of the syncytial cells at the early stages had the most strong activity, especially -around. the lacwiae. The syncytial. cells after 15-16th week of pregnancy got even distribution in their inner side. of cytoplasms by degree along the placental aging. The variabilities and differences of stains in each villi. which were shown at the early stages, were lost after the third month of pregnancy.
The overterm placentas had weaker activity than the term.
The placentas of spontaneous abortion at the early stages before the second half of the mid-trimester had .lost their stains in general and more from the brush border, comparing with same agine ones. The placentas of the intrauterine fetal death and the severe toxemia of pregnancy were also remarkably less stained. The chorionic tumors were strongly stained but very variable in several regions.
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