Should You Take Progesterone When You Get Pregnant?

After two miscarriages at six weeks, my doctor has recommended I take progesterone next time I get pregnant. Why? And what’s the difference between that progesterone and the one I took as a form of birth control? Would the side effects be the same?

—Sad but still hopeful

I am so sorry to hear about your miscarriages. That is difficult both emotionally and physically.

Progesterone is one of the most important hormones during pregnancy. In early pregnancy, it stabilizes the uterine lining so an embryo can implant. When all is going according to plan in the early weeks of pregnancy, progesterone is made in the ovaries by the cells that had surrounded the developing egg prior to ovulation. These cells left behind are called the corpus luteum, and they are the main source of progesterone for the first six weeks of pregnancy. By about week seven of pregnancy, the placenta takes over, making progesterone.

The rationale for supplementing progesterone in women who have experienced early miscarriage is that perhaps a lack of progesterone from the corpus luteum contributed to the pregnancy loss. The data regarding using progesterone in women with a history of recurrent miscarriage in early pregnancy is mixed.

In a randomized controlled trial of women with a history of recurrent miscarriage, there was no difference in the rate of live births between those who were given vaginal progesterone in early pregnancy and those given a placebo. But a meta-analysis of women with vaginal bleeding in early pregnancy showed a very small increase in the number of live births among those who received vaginal progesterone compared with those who received a placebo. However, there was no increase in live births among women with a history of recurrent miscarriage who received progesterone in that meta-analysis. As a result, experts disagree about whether vaginal progesterone should be recommended.

There are two main differences between the progesterone used in women with a history of early miscarriage and the progestin in your birth control pill. The first is that typically, in early pregnancy progesterone will be given vaginally, not as a pill taken orally. The second is that the progesterone used in early pregnancy is identical to the progesterone your body makes. The progestin in your birth control pill is made in a lab and is similar to the progesterone your body makes, but not identical.

Because the progesterone given in early pregnancy is chemically slightly different from the progestin in your birth control pill, and because it is given vaginally, you may experience different side effects from this progesterone. The most common side effects from vaginal progesterone are similar to the symptoms of early pregnancy, including headache, nausea, breast tenderness, bloating, and constipation. This makes sense when you consider that the goal is to supplement the progesterone made in your ovaries.

The takeaway: Progesterone is a critical hormone in early pregnancy. However, the data is mixed regarding whether it improves your chances of a successful pregnancy. Unlike the progestins in birth control pills, the progesterone used in early pregnancy is identical to the progesterone your body makes and is given vaginally instead of by mouth.