Progesterone for Preventing Preterm Labor and Delivery

During pregnancy, the placenta makes high levels of the hormone progesterone, which helps support the pregnancy. A drop in progesterone levels is thought to be one of many factors that help start labor contractions.¹

Studies have shown that progesterone treatment in the second trimester helps lower the risk of preterm birth. This means that although some women still delivered prematurely, progesterone treatment helped more high-risk women carry their pregnancies longer than a placebo treatment did.^{2, 3} (In this case, "high-risk" meant that a woman had had at least one preterm birth in the past.)

In high-risk women, progesterone has been shown to reduce preterm birth.⁴

There is no evidence that progesterone treatment prevents early miscarriage.

Progesterone is a new treatment. And the type of progesterone used in this research, 17 alpha-hydroxyprogesterone caproate, is not available in all areas of the country.

The American College of Obstetricians and Gynecologists (ACOG) advises doctors to consider weekly progesterone injections only for women who are at high risk for preterm labor. This is based on studies of women who have had a previous spontaneous preterm birth (before 37 weeks).⁵ More research is needed before other high-risk women, such as those who already have signs of preterm labor or women who are pregnant with twins or more, can be considered for progesterone treatment.

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