Reproductive Endocrinology Ovarian Hormones
RRM Academy Synopsis
Blood progesterone rises through pregnancy and faster after week 35
A 1959 Cambridge study of 47 pregnant women found blood progesterone rose steadily from week 11 to week 35, then rose faster and stayed high until birth. The authors also estimated that progesterone clears from a mother's blood with a half-life of 5 minutes or less, using samples drawn after the placenta came out.
Key Findings
- The authors measured progesterone in fifty blood samples from forty-seven women, collected between the 11th week of pregnancy and the day of delivery.
- Plasma progesterone climbed gradually from the 11th to the 35th week, then appeared to rise much more rapidly after the 35th week and stayed high until birth.
- Three twin pregnancies showed plasma progesterone that tended to run higher than single pregnancies at the same stage.
- Three women had elective cesarean sections: progesterone was undetectable in two within minutes of placenta removal and lower but still measurable at 3 minutes in the third.
- In late pregnancy, at 39 to 41 weeks, the authors put the half-life of progesterone in maternal blood at probably about 5 min or less.
Interpretation
The report is a descriptive laboratory study in which each woman gave one blood sample. The women were in good health, two of them anemic, and anyone with diabetes or toxemia of pregnancy was excluded. The authors discarded results in which unidentified impurities distorted the reading. The half-life estimate comes from timed samples after placenta removal at three elective cesareans and agrees with a calculation from published rates of progesterone production. The authors set normal levels across pregnancy as a baseline for later studies of abnormal conditions, and they found the variation between patients at any stage did not appear to be great. They note that the meaning of the late rise is not fully understood.
RRM Context
Progesterone supports pregnancy, and restorative reproductive medicine follows it closely. The paper offered an early blood measurement for a field that had relied on urine tests. The authors closed by pointing to the blood assay as a way to diagnose a patient's progesterone status at any particular time.
Abstract
Summary
The content of progesterone was determined in the peripheral venous blood of pregnant women from the 11th week after the last menstrual period up to the day of birth. There was a steady increase in the blood level from the 11th to the 35th week, but thereafter the level rose more rapidly, and remained high during labour itself. The significance of this rise after the 35th week is not fully understood. It may reflect a decrease in the rate of progesterone metabolism which occurs at this time. The blood level in three cases of twin pregnancy tended to be higher than the corresponding levels for single pregnancies. After removal of the placenta during elective caesarean sections, it was found that the blood progesterone level rapidly fell below the limits of sensitivity of the method. It has been estimated that the half-life of progesterone in the circulating blood must be 5 min or less.
Topics
Keywords
Female, Humans, Pregnancy/blood, Progesterone/blood, Progesterone, PREGNANCY/blood, PROGESTERONE/blood
