DISTRIBUTION OF CHORIONIC GONADOTROPIN IN MOTHER AND FETUS AT VARIOUS STAGES OF PREGNANCY*

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Abstract
The distr. and concn. of human chorionic gonadotropin in maternal and fetal tissues and fluids was detd. throughout pregnancy by bioassays. The highest concn. is always in the chorionic placenta, supporting the view that the hormone is produced by the embryonic trophoblast. The pattern of distr. suggests that the chorion releases the gonadotropin into the maternal blood, and that secondarily some of it passes the "placental barrier" and enters the fetal system across the wall of the chorionic vesicle. In the maternal body the highest gonadotropin concn. is in the blood; and the uterine endometrium has a higher content than the other body tissues. Although the fetal body contains relatively small amts. of chorionic gonadotropin, they may well be of physiologic significance. The ratio of concn. between maternal muscle and trunk tissue of the fetus ranges from 10:1 to 20:1. The concns. decrease similarly in all fetal and maternal tissues and fluids from the 11th week until parturition, falling to about one twenty-fifth of their original values. The maternal system is cleared of the hormone after therapeutic abortion or after normal delivery, in the same length of time. The hypophysis discontinues gonadotropin production during pregnancy but after removal of the gravid uterus, resumes its normal functions within not more than 6 days.

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