Melatonin

Last Update: 09 Sep 2025

Medication

Table of content

1. What is it? 2. What are the risks according to research? 3. Breastfeeding/ chestfeeding 4. What about fathers and sperm donors? 5. Key points

Welcome to our fact sheet on melatonin during pregnancy and breastfeeding or chestfeeding. This information is based on available published literature. It should not take the place of medical care and advice from your healthcare provider.

The HEALTHY PREGNANCY HUB team is collaborating with MotherToBaby to share information on this topic. The original version is available here (April 2024).

Serene, our chatbot, can also answer your questions about medications during pregnancy.

Please note that this fact sheet is based on United States information and has been adapted for Canada, with a review by our Canadian experts. Minor differences may exist between the two countries. Always consult your healthcare professional for information tailored to your situation.

1. What is melatonin?

Melatonin is a hormone made by the body that helps with the natural sleep-wake cycle (called circadian rhythm). Melatonin is made by the body mostly during periods of darkness in the night. During pregnancy, the body typically makes more melatonin. Studies suggest that melatonin levels are highest in the third trimester of pregnancy and levels are expected to return to pre-pregnancy normal levels after delivery.

Melatonin is also available as a supplement sold over the counter. Taking melatonin supplements during pregnancy has not been well studied. You should speak with your healthcare provider before taking any supplements. Many supplements are not recommended for use during pregnancy unless your healthcare provider has prescribed them to treat a medical condition. This is because they are not well-regulated nor studied for use in pregnancy. For more detail on supplements, please see the MotherToBaby fact sheet here.

2. What does research say about the risks during pregnancy?

I take melatonin. Can it make it harder for me to get pregnant?

A small number of limited studies that have looked at use of melatonin among people identified as women with infertility who were undergoing in vitro-fertilization (IVF) treatments have not shown an increase or decrease in pregnancy rates.

Does taking melatonin increase the chance of miscarriage?

This has not been well studied. Miscarriage is common and can occur in any pregnancy for many different reasons. Studies that have looked at melatonin use for infertility have not shown any increases in the chance of miscarriage.

Does taking melatonin 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 not known if taking melatonin would increase the chance of birth defects. The few studies that have been done in humans with the use of melatonin for the treatments of some conditions in pregnancy (to reduce blood loss during C-section and improve success of in vitro fertilization) have not suggested an increased chance of birth defects.

Does taking melatonin in pregnancy increase the chance of other pregnancy-related problems?

Studies have not been done to see if taking melatonin supplements can increase the chance of other pregnancy-related problems, such as preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth). Studies exploring the use of melatonin to reduce blood loss during C-section deliveries found mixed results with 3 studies showing less blood loss and 1 study showing no difference in blood loss.

Does taking melatonin in pregnancy affect future behavior or learning for the child?

Studies have not been done to see if taking melatonin supplements can cause behavior or learning issues for the child.

3. Breastfeeding/ chestfeeding while taking melatonin

Melatonin made by the body is present in human milk in higher amounts at night. Taking melatonin supplements while nursing has not been well studied. One case has been reported of an infant with a bleeding problem while being breastfed by a person who was taking a supplement that had melatonin and valerian. This bleeding problem has not been reported in other studies, including studies where melatonin was given directly to infants.

Be sure to talk to your healthcare provider about all your breastfeeding or chestfeeding questions.

4. What about fathers and sperm donors?

If a male takes melatonin, could it affect fertility or increase the chance of birth defects?

Based on the studies reviewed, it is not known if melatonin supplements could affect a male’s fertility (ability to get a person 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 here.

Key points

Melatonin is a hormone naturally made by the body that helps control the sleep-wake cycle. Melatonin supplements are sold over-the-counter, without prescription, but they are not well studied in pregnancy.
We don’t know if melatonin affect fertility.
Studies so far have not shown a higher chance of miscarriage or malformation.
There is not enough research to know if melatonin causes problems like early birth or low birth weight.
Melatonin made by the body naturally appears in human milk, especially at night. Taking melatonin supplements while breastfeeding or chestfeeding is not well studied.
It is not known if melatonin affects male fertility or increases the chance of birth defects. In general, medications or supplements taken by male are unlikely to increase pregnancy risks.
Always consult your healthcare provider before starting or continuing melatonin during pregnancy or breastfeeding/ chestfeeding.

References

Please click here for references.

Disclaimer

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