This fact sheet is about exposure to progesterone and progestins in pregnancy and while breastfeeding. This information is based on available published literature. It 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) for 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.

Progestin is a synthetic (human-made) form of progesterone. Birth control products contain progestins. Progestins are also used to treat amenorrhea (not having menstrual cycles) and abnormal uterine bleeding. Progestin might come in the form of a pill, injection, gel, suppository, cream or patch depending on the dosage and what it is being used for. Some progesterone and progestin brand names are Crinone®, Endometrin®, Prometrium®, and Prochieve®.

Sometimes when people find out they are pregnant, they think about changing how they take their medication, or stopping their medication 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 become pregnant?

Progesterone helps people get pregnant. However, progestins used in birth control pills help prevent pregnancy. Therefore, it is important that you speak with your healthcare provider about the type of progesterone or progastrin you use before starting or stopping any medication containing progestin.

Does taking progesterone or progestin increase the chance for miscarriage?

Miscarriage is common and can occur in any pregnancy for many different reasons. Progesterone or progastrin use does not increase the chance of 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 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. there were issues with how these studies were done and therefore, the results might not be correct. 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 in pregnancy increase the chance of other pregnancy-related problems?

Most research looking at the use of progesterone and progestin in pregnancy focuses on those 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 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 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 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 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 get partner pregnant) or increase the chance of birth defects above the background risk. 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/.

Selected References:

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• Check JH, et al. 1986. The risk of fetal anomalies as a result of progesterone therapy during pregnancy. Fertil Steril, 45:575-577. [PubMed: 3956772]
• Committee on Drugs. 2001. The transfer of drugs and other chemicals into human milk. Pediatrics, 108(3):776-789. [PubMed: 11533352]
• American College of Obstetricians and Gynecologists’ Committee on Practice Bulletins-Obstetrics. 2021. rPrediction and prevention of spontaneous preterm birth: ACOG Practice Bulletin, Number 234. Obstet Gynecol, 138(2):e65-e90. [PubMed: 34293771]
• Devall AJ, et al. 2021. Progestogens for preventing miscarriage: A network meta-analysis. Cochrane Database Sys Rev, 4(4):CD013792. [PMC free article: PMC8406671] [PubMed: 33872382]
• Duds I, et al. 2006. Population-based case-control teratogenic study of hydroxyprogesterone treatment during pregnancy. Congenit Anom (Kyoto), 46:194-198. [PubMed: 17096820]
• Fawzy M, et al. 2008. Treatment options and pregnancy outcome in women with idiopathic recurrent miscarriage: a randomized placebo-controlled study. Arch Gynecol Obstet, 278(1):33-38. [PubMed: 18071727]
• Heinonen OP, et al. 1977. Birth Defects and Drugs in Pregnancy. Littleton, Mass.: John Wright-PSG, pp 389, 391-392, 394, 443, 478, 497.
• Heinonen OP, et al. 1977. Cardiovascular birth defects and antenatal exposure to female sex hormones. N Engl J Med, 296:67-60. [PubMed: 830309]
• Massai R, et al. 2005. Extended use of a progesterone-releasing vaginal ring in nursing women: a phase II clinical trial. Contraception, 72:352-357. [PubMed: 16246661]
• Michaelis J, et al. 1983. Prospective study of suspected associations between certain drugs administered during early pregnancy and congenital malformations. Teratology, 27:57-64. [PubMed: 6845218]
• Norman JE, et al. 2009. Progesterone for the prevention of preterm birth in twin pregnancy (STOPPIT): a randomised, double-blind, placebo-controlled study and meta-analysis. Lancet, 373(9680):2034-2040. [PubMed: 19523680]
• Practice Committee of the American Society for Reproductive Medicine. 2008. Progesterone supplementation during the luteal phase and in early pregnancy in the treatment of infertility: an educational bulletin. Fertility and Sterility, 89(4):789-792. [PubMed: 18406835]
• Practice Committee of the American Society for Reproductive Medicine. 2012. Evaluation and treatment of recurrent pregnancy loss: a committee opinion. Fertility and Sterility, 98(5):1103-1111. [PubMed: 22835448]
• RamaRao S, et al. 2013. Progesterone vaginal ring: Introducing a contraceptive to meet the needs of breastfeeding women. Contraception, 88(5):591-598. [PubMed: 23769015]
• Roy M, et al. 2020. Progesterone vaginal ring as a new contraceptive option for lactating mothers: Evidence from a multicenter non-randomized comparative clinical trial in India. Contraception, 102(3):159-167. [PMC free article: PMC7483628] [PubMed: 32360666]
• Silver RI, et al. 1999. In vitro fertilization is associated with an increased risk of hypospadias. J Urology, 161(6):1954-1957. [PubMed: 10332480]