- Melatonin supplements have not been well studied in pregnancy, so whether to use one is a decision to make with your OB rather than on your own.
- The few human studies so far have not suggested an increased chance of birth defects, but the evidence is limited and does not amount to a clean bill of safety.
- Supplements are regulated differently from prescription medicines, so actual product contents and doses can vary, which adds uncertainty.
- One older study linked high daily doses to changes in ovarian hormones, which could make conceiving harder, so mention any regular use if you are trying to get pregnant.
- Insomnia in pregnancy is common and treatable, and there are non-drug approaches worth discussing before reaching for a supplement.
- The old FDA pregnancy letter categories have been retired; questions about a specific exposure can go to MotherToBaby at 1-866-626-6847.
Melatonin is one of the most popular over-the-counter sleep aids, and it is easy to assume that something sold as a “natural” supplement must be fine in pregnancy. The honest answer is more uncertain than that. Melatonin in pregnancy simply has not been well studied, which is a different thing from being proven safe or unsafe. This article gathers what leading U.S. sources actually say so you can decide with your clinician. It is general education only and is not a substitute for medical advice.
What melatonin is and what it is used for
Melatonin is a hormone the body makes naturally, mainly at night, to help regulate the sleep-wake cycle. It is also sold as a dietary supplement, often used for trouble falling asleep, jet lag, or shift-work sleep problems. Because it is marketed as a supplement rather than a prescription medicine, it is easy to buy and easy to underestimate. But being naturally occurring does not automatically make a supplement version safe at supplement doses during pregnancy, which is why the evidence, not the label, is what matters here.
What the guidance says about pregnancy
MotherToBaby, a service of the non-profit Organization of Teratology Information Specialists, is candid that taking melatonin supplements during pregnancy has not been well studied. As a general principle, MotherToBaby notes that many supplements are not recommended in pregnancy unless a healthcare provider has advised one for a specific reason, in part because supplements are regulated differently from prescription medicines and are less studied in pregnancy.
Birth defects. MotherToBaby reports that it is not known whether melatonin can increase the chance of birth defects, and that the few human studies done so far have not suggested an increased chance. That is mildly reassuring, but the small size and number of studies mean it is not the same as an all-clear.
Other pregnancy outcomes. MotherToBaby notes that studies have not been done to see whether melatonin supplements affect the chance of other pregnancy problems, such as preterm delivery or low birth weight. In other words, these questions are largely unanswered rather than answered reassuringly.
A note on trying to conceive
If you are trying to get pregnant, there is one specific finding worth knowing. MotherToBaby describes an older study in which high daily doses of melatonin, in a range far above typical over-the-counter use, affected ovarian function by lowering levels of hormones needed to conceive, which could make becoming pregnant harder. This is a reason to mention any regular melatonin use to your clinician if you are trying to conceive, so it can be part of the wider picture.
Why product variability matters
One practical wrinkle with melatonin is that supplements are not regulated as tightly as prescription drugs. Independent testing over the years has repeatedly found that the actual melatonin content of products can differ from what the label states, sometimes substantially, and some products contain other ingredients. That uncertainty about what is actually in the bottle is another reason to involve your clinician rather than self-treating, and to be cautious about high doses.
The other side: sleep problems are worth addressing
Caution about melatonin does not mean you should just accept poor sleep. Insomnia is common in pregnancy and can affect wellbeing, and it is worth raising with your clinician. There are non-drug approaches often suggested first, such as consistent sleep and wake times, a wind-down routine, limiting screens and caffeine, and cognitive behavioral techniques for insomnia. If sleep problems are severe or tied to anxiety or depression, treating the underlying issue may help more than a supplement. The goal is better, safer sleep, guided by someone who knows your pregnancy.
Do not start or stop on your own
Because the evidence is thin, the safest approach is not to start melatonin in pregnancy just because it is available without a prescription; check with your OB or midwife first. If melatonin was suggested to you by a clinician for a specific reason, follow their guidance rather than changing the plan on your own. And if you take a prescription medicine for sleep or another condition, do not stop it abruptly to switch to melatonin without talking to your prescriber, since some medicines should not be stopped suddenly.
A note on the old letter categories
You may see old references to FDA pregnancy “categories.” That letter system has been retired, and as a dietary supplement melatonin was never labeled the way prescription drugs are anyway. U.S. prescription labels now use a narrative format under the Pregnancy and Lactation Labeling Rule. For a supplement, the most reliable guidance is your own clinician and services like MotherToBaby, not a letter grade.
Breastfeeding
MotherToBaby reports that melatonin use while breastfeeding has not been well studied, but that it is unlikely that short-term use of usual evening doses by a nursing parent would harm a breastfed baby. As always, confirm anything specific to your situation with your clinician, especially for a newborn.
When to call your OB or a clinician
Talk with your obstetric provider before starting melatonin in pregnancy, and reach out if sleep problems are persistent or severe, if you have already been using melatonin and are unsure, or if poor sleep comes with low mood, anxiety, or other symptoms. For questions about a specific exposure, call MotherToBaby at 1-866-626-6847, a free service that answers questions about medicines and supplements in pregnancy and breastfeeding.
Frequently asked questions
Is melatonin safe to take while pregnant? It has not been well studied, so “safe” cannot be stated with confidence. The few human studies have not shown an increased chance of birth defects, but the evidence is limited. Check with your OB first.
I took melatonin before I knew I was pregnant. Should I worry? Try not to panic. MotherToBaby reports the limited human studies have not suggested an increased chance of birth defects. Mention it to your OB and ask any follow-up questions there or through MotherToBaby.
Is a “natural” supplement automatically safe? No. Being naturally occurring does not mean a supplement dose is proven safe in pregnancy, and supplement contents can vary from the label. That is why clinician guidance matters.
Can melatonin affect getting pregnant? MotherToBaby describes an older study in which very high daily doses affected ovarian hormones and could make conceiving harder. Mention regular use to your clinician if you are trying to conceive.
What can help me sleep instead? Non-drug approaches are often suggested first, such as steady sleep times, a wind-down routine, and limiting caffeine and screens. Ask your clinician, especially if poor sleep is linked to anxiety or low mood.
Can I use melatonin while breastfeeding? MotherToBaby notes it has not been well studied, but short-term usual evening doses are unlikely to harm a breastfed baby. Confirm with your clinician, especially for a newborn.
This article is general education, not medical advice, and must not be used to start, stop, adjust, or taper any medication on your own. Suddenly stopping some medicines can be dangerous. Always work with the prescriber who manages your care. In an emergency call 911; for mental-health crisis call or text 988.
Sources
- MotherToBaby (Organization of Teratology Information Specialists) — Melatonin fact sheet.
- MotherToBaby educational material on insomnia in pregnancy and the LactMed lactation reference.