This fact sheet is 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 naturally made in the body by the ovaries (female glands where eggs form and female hormones are made). The body uses progesterone to build the lining of the uterus (womb) during the menstrual cycle (period) and helps the fertilized egg attach to the wall of the uterus. During pregnancy, the placenta makes progesterone to help prevent miscarriage.
There are also synthetic substances (made in a laboratory) like progesterone called progestins. Birth control products contain progestins. Progestins have also been used to treat amenorrhea (not having menstrual cycles) and abnormal uterine bleeding.
Some progesterone and progestin brand names include Crinone®, Endometrin®, Prometrium®, and Prochieve®.
I take progesterone or a progestin. Can it make it harder for me to become pregnant?
Progesterone helps people get pregnant. Progestins can also prevent pregnancy. It is important that you speak with your healthcare provider before beginning or discontinuing any medication.
Does taking progesterone or progestin increase the chance for miscarriage?
Miscarriage can occur in any pregnancy. Progesterone use does not increase the chance for a miscarriage. In fact, some people use prescribed progesterone early in pregnancy to help prevent miscarriage.
Does taking progesterone or progestin increase the chance of birth defects?
Every pregnancy starts out with a 3-5% chance of having a birth defect. This is called the background risk. It is unlikely that using progesterone or a progestin will increase the chance of birth defects.
Some studies raised a concern about a chance for boys 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. These studies have some design flaws. Most studies that have looked at the children of people who took progesterone or progestins during pregnancy did not report a higher chance of birth defects
Does taking progesterone or progestin cause other pregnancy problems?
Most research looking at the use of progesterone and progestin in pregnancy focuses on those who receive it as an injection (called 17-hydroxyprogesterone caproate or Makena®) or as a vaginal suppository to prevent preterm labor. Studies have not shown negative effects.
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 have not found progesterone or progestin use in pregnancy to cause problems with the brain (neurodevelopment).
Breastfeeding 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 male takes progesterone or progestin, could it affect 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 or sperm donors 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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OTIS/MotherToBaby encourages inclusive and person-centered language. While our name still contains a reference to mothers, we are updating our resources with more inclusive terms. Use of the term mother or maternal refers to a person who is pregnant. Use of the term father or paternal refers to a person who contributes sperm.