Chances are you may have heard of progesterone, particularly if you have had recurrent miscarriages. Progesterone is a hormone associated with pregnancy and the menstrual cycle.
Levels of progesterone rise every month after ovulation, preparing the lining of the uterus for pregnancy. In a non-pregnant menstrual cycle, progesterone levels rise after ovulation and fall just before a woman gets her menstrual period. When pregnancy occurs, the progesterone level should remain elevated. The ovaries produce the majority of progesterone through most of the first trimester, but eventually the placenta takes over production of the hormone by about the tenth week of pregnancy.
Because progesterone plays a role in maintaining the uterine lining, some researchers have theorized that having low progesterone before a miscarriage might actually play a role in causing the miscarriage. But whether supplementing progesterone actually prevents miscarriage is a matter of debate.
Right now, no medical organizations recommend supplementing progesterone in women with luteal phase issues or recurrent miscarriages, except in women using reproductive technologies such as IVF.
No scientific studies have found definitive evidence that progesterone supplements prevent miscarriage in women who are not using artificial reproduction methods. Most studies find no difference in miscarriage rates when comparing women who took progesterone supplements to women who did not.
A few studies have found evidence that taking progesterone supplements might benefit women who have had recurrent miscarriages, but right now the numbers are too small to say whether or not the findings are significant. More research needs to be done before doctors will know whether or not the supplements are beneficial.
Low progesterone in pregnancy is definitely associated with miscarriage, but the reason why is controversial. On one hand, too-low levels could theoretically cause miscarriage if the uterus is not ready to support a pregnancy, perhaps because the ovaries have problems producing enough progesterone for some reason.
On the other hand, many doctors believe that low progesterone merely means that a miscarriage is impending for other reasons. With this line of thinking, the low levels are the first sign that the body is preparing to miscarry a pregnancy that has already failed for other reasons, such as chromosomal abnormalities in the developing baby, and progesterone supplementation is useless.
Right now, no one knows the correct answer, and the subject tends to be a matter of hearty debate.