This fact sheet talks about exposure to progesterone and progestins in pregnancy and while breastfeeding. This information should not take the place of medical care and advice from your healthcare provider.

What are progesterone and progestin?

Progesterone is a hormone that is naturally made in the body by the ovaries. The body uses progesterone to build the lining of the uterus during the menstrual cycle and helps the fertilized egg attach to the wall of the uterus. During pregnancy, the placenta makes progesterone to help prevent miscarriage. Progesterone can also be made in a laboratory and is sold under many brand names including, Crinone®, Endometrin®, Prometrium®, and Prochieve®.

There are also other synthetic substances (made in a laboratory) that are similar to progesterone called progestins. Progestins are included in some forms of birth control.

Progesterone and progestins can be taken by mouth, injected, or inserted vaginally.

I take progesterone or a progestin. Can it make it harder for me to become pregnant?

Women may be given progesterone to help them get pregnant. Progestins generally prevent pregnancy It is important that you speak with your healthcare provider before beginning or discontinuing any medication.

I just found out I am pregnant. Should I stop taking progesterone or a progestin?

Talk to your healthcare providers if you are taking these medications and you are pregnant. If you are taking a progestin to prevent pregnancy (birth control) and you are now pregnant, it is no longer needed and should be stopped. If you are taking progesterone as part of a fertility treatment, to help you get/sustain a pregnancy, or to prevent miscarriage, please speak with your provider to determine how long you should continue with this medication.

Does taking progesterone or progestin increase the chance for miscarriage? 

Miscarriage can occur in any pregnancy. Progesterone use is not expected to increase the chance for a miscarriage. In fact, some women might be prescribed progesterone early in pregnancy to help prevent miscarriage.

Does taking progesterone or progestin increase the chance of birth defects?

In every pregnancy, a woman starts out with a 3-5% chance of having a baby with a birth defect. This is called her background risk. It is unlikely that using progesterone or a progestin will increase the chance of birth defects above the background risk.

Some studies raised a concern about a chance for boys to be born with hypospadias after exposure to progestins. Hypospadias is when the opening where urine comes out is not at the correct location on the penis. Sometimes this can be treated with surgery. These studies have some design flaws. The majority of studies that have looked at the children of women who took progesterone or progestins during pregnancy did not report a higher chance of birth defects over the background risk.

Does taking progesterone or progestin cause other pregnancy complications?

Most research looking at the use of progesterone and progestin in pregnancy focuses on women who receive it as an injection (called 17-hydroxyprogesterone caproate or Makena®) or as a vaginal suppository to prevent preterm labor. No negative effects have been reported in these studies.

Does taking progesterone or progestin in pregnancy cause long-term problems in behavior or learning for the baby?

Studies that have followed children up to the age of 5 have not found progesterone or progestin use in pregnancy to cause problems with the brain (neurodevelopment).

Can I breastfeed while taking progesterone or progestin?

Supplemental progesterone or progestins enter the breastmilk in low amounts. Breastfeeding while taking progesterone or progestin is not expected to be harmful to the nursing infant. Be sure to talk to your healthcare provider about all your breastfeeding questions.

If a man takes progesterone or progestin, could it affect his fertility (ability to get partner pregnant) or increase the chance of birth defects?

Men naturally make progesterone. There have been no studies looking at a father’s use of supplemental progesterone use. In general, exposures that fathers have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.

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