This fact sheet is about exposure to progesterone and progestins in pregnancy and while breastfeeding. This information is based on published research studies. It should not take the place of medical care and advice from your healthcare providers.
What are progesterone and progestin?
Progesterone is a hormone naturally made by the ovaries (female glands where eggs form and hormones are made). The body uses progesterone to prepare the lining of the uterus (womb) for the menstrual cycle (period) and to help a fertilized egg attach to the wall of the uterus. During pregnancy, the placenta makes progesterone to help support the pregnancy and prevent miscarriage.
Progestin is a synthetic (human-made) form of progesterone. Birth control products contain progestins. Progestins have also been used to treat amenorrhea (not having menstrual cycles) and abnormal uterine bleeding. Depending on the dose and how it is used, progestin can come as a pill, injection, gel, suppository, cream, or patch. Some progesterone and progestin brand names are Crinone®, Endometrin®, Prometrium®, and Prochieve®.
Sometimes when women find out they are pregnant, they think about changing how they take their medication or stopping it altogether. However, it is important to talk with your healthcare providers before making any changes to how you take your medication. Your healthcare providers can talk with you about the benefits of treating your condition and the risks of untreated illness during pregnancy.
I take progesterone or a progestin. Can it make it harder for me to get pregnant?
Progesterone helps women get pregnant. However, progestins used in birth control pills help prevent pregnancy. It is important that you speak with your healthcare provider about the type of progesterone or progestin you use before starting or stopping any medication containing progestin.
Does taking progesterone or progestin increase the chance of miscarriage?
Miscarriage is common and can occur in any pregnancy for many different reasons. Progesterone or progestin use does not increase the chance of miscarriage. In fact, some women use prescribed progesterone early in pregnancy to help prevent miscarriage.
Does taking progesterone or progestin increase the chance of birth defects?
Birth defects can happen in any pregnancy for different reasons. Out of all babies born each year, about 3 out of 100 (3%) will have a birth defect. We look at research studies to try to understand if an exposure, like progesterone or progestin, might increase the chance of birth defects in a pregnancy. It is unlikely that using progesterone or progestin will increase the chance of birth defects.
Some studies raised a concern about a chance for males to be born with hypospadias after exposure to progestins. Hypospadias is a birth defect where the opening of the urethra (the tube where urine comes from the bladder to the outside of the body) is not on the tip of the penis. If necessary, surgery can correct hypospadias. However, there were concerns about how these studies were done, so the results may not be accurate. Most studies of children born to women who took progesterone or progestins during pregnancy have not found an increased chance of birth defects.
Does taking progesterone or progestin in pregnancy increase the chance of other pregnancy-related problems?
Most research looking at the use of progesterone and progestin in pregnancy focuses on women who receive it during late pregnancy as an injection (called 17-hydroxyprogesterone caproate or Makena®) or as a vaginal suppository to prevent preterm labor. These studies have not shown an increased chance of other pregnancy-related problems, such as preterm delivery (birth before week 37 of pregnancy) or low birth weight (weighing less than 5 pounds, 8 ounces [2,500 grams] at birth).
Does taking progesterone or progestin in pregnancy affect future behavior or learning for the child?
Studies that have followed children up to the age of 5 years have not found progesterone or progestin use in pregnancy to cause problems with the development of the brain (neurodevelopment).
Breastfeeding while taking progesterone or progestin:
Supplemental progesterone or progestins enter the breast milk 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 fertility or increase the chance of birth defects?
Men naturally make progesterone. Studies have not been done to see if supplemental progesterone or progestins could affect male fertility (ability to make healthy sperm) or increase the chance of birth defects. In general, exposures that men have are less likely 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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