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Hormones in human pregnancy. IV. Plasma progesterone
American Journal of Obstetrics and Gynecology
|February 1, 1975
Summary
Maternal progesterone levels fluctuate significantly in early pregnancy. At term, fetal circulation shows higher progesterone in the umbilical vein than artery, with an estimated fetal secretion rate of 23 mg/24 hr.
Area of Science:
- Reproductive endocrinology
- Maternal-fetal medicine
- Biochemistry
Background:
- Progesterone (P) is crucial for maintaining pregnancy.
- Understanding progesterone dynamics in maternal and fetal circulation is vital for assessing pregnancy health.
Purpose of the Study:
- To quantify plasma progesterone concentrations in maternal peripheral vein (M.P.V.) during early and term pregnancy.
- To investigate progesterone levels in umbilical artery (U.A.) and umbilical vein (U.V.) at term.
- To estimate fetal progesterone secretion and analyze unbound progesterone fractions.
Main Methods:
- Radioimmunoassay (RIA) for plasma progesterone measurement.
- Equilibrium dialysis for determining unbound progesterone fraction.
- Analysis of maternal and umbilical cord blood samples.
Main Results:
- Early pregnancy shows marked hour-to-hour fluctuations in plasma progesterone.
- At term, U.V. plasma P levels are higher than U.A. plasma P levels.
- Estimated fetal P secretion is approximately 23 mg/24 hr, about 10% of total production.
- Unbound progesterone in term maternal plasma is not different from non-pregnant levels but is lower than in umbilical cord plasma.
Conclusions:
- Fetal circulation contributes to progesterone levels, with an estimated secretion rate.
- Changes in unbound progesterone fractions during pregnancy warrant further investigation.
- Plasma progesterone levels in pre-eclamptic patients with intrauterine fetal death are not indicative of placental function.