May 17, 2025

Melatonin During Pregnancy: Common Questions

This article is educational and not a substitute for your clinician’s advice. Pregnancy varies, and the right choice depends on your symptoms, trimester, and medical history.

1) What is melatonin?

Melatonin is a hormone your brain releases at night that helps signal “it’s time for sleep.” During pregnancy, the placenta also produces melatonin, and both the placenta and fetus have melatonin receptors (binding sites that respond to melatonin). (ScienceDirect)

2) Is melatonin considered “safe” during pregnancy?

We don’t have enough large, high-quality studies to say it is definitively proven safe for routine insomnia in pregnancy. Based on the human studies that do exist (often in other pregnancy conditions), many experts consider melatonin probably low risk, but the evidence is still limited. (PMC)

3) Does melatonin reach the baby?

Yes. Studies show melatonin crosses the placenta, meaning the fetus can be exposed when the pregnant person takes melatonin. (PubMed)

4) Does melatonin cause birth defects?

There is no strong evidence from the available human clinical literature showing that melatonin causes major birth defects. However, the overall number of well-designed human pregnancy studies is still small, so rare risks are hard to rule out. (PMC)

5) Does melatonin increase miscarriage risk?

We do not have strong direct human evidence that can accurately measure miscarriage risk from typical over-the-counter melatonin use for insomnia in pregnancy. Reviews consistently describe this as an evidence gap. (PMC)

6) Does melatonin help pregnancy insomnia?

We do not have strong clinical trial evidence showing that melatonin reliably treats insomnia specifically during pregnancy. Many pregnancy studies of melatonin were done for other reasons (not insomnia), so they don’t answer the “does it fix pregnancy insomnia?” question well. (PMC)

7) What works best for insomnia during pregnancy?

Cognitive Behavioral Therapy for Insomnia (CBT-I) works well and has clinical trial support in pregnant patients.

  • CBT-I is a structured program that changes sleep habits and sleep-related thoughts that keep insomnia going.
  • It is not a medication, and it can improve insomnia symptoms meaningfully. (PMC)

8) Why do clinicians still talk about melatonin if the data is limited?

Because:

  • Many pregnant patients want to avoid stronger sleep medications.
  • Some pregnancy studies using melatonin for other conditions have not shown major short-term safety problems.
  • Melatonin is widely used, so clinicians often need to discuss it even when evidence is incomplete. (PMC)

9) Could melatonin affect the placenta or pregnancy biology?

Melatonin plays roles in the placenta related to oxidative stress and inflammation (chemical stress and immune signaling). Some researchers are studying whether this could be helpful in certain pregnancy complications. But these biological findings do not prove routine melatonin use is beneficial for insomnia in pregnancy. (PMC)

10) Has melatonin been studied in pregnancy for anything other than sleep?

Yes. It has been studied in research settings for conditions such as:

  • Preeclampsia (a pregnancy-related high blood pressure condition) (PMC)
  • Fetal growth restriction (when the fetus is smaller than expected) (PMC)

Important: these studies do not automatically mean melatonin should be used for insomnia without clinician guidance. (PMC)

11) Could melatonin harm fetal growth?

Human evidence is not definitive. Some animal studies raise concerns depending on dose and timing, but animal results do not always predict human outcomes. This uncertainty is part of why many reviews stay cautious. (AJOG)

12) If someone uses melatonin in pregnancy, what approach is most conservative?

Because strong pregnancy-insomnia trials are limited, many clinicians use general safety principles:

  • Use the lowest dose that helps.
  • Use it for the shortest time possible.
  • Take it at a consistent time before your intended bedtime (timing matters for circadian rhythm, your internal clock). (PMC)

13) Are melatonin supplements reliably labeled?

Often, no. Studies have found that many over-the-counter melatonin products contain much more or much less melatonin than the label says, and some products have unexpected ingredients. This matters more in pregnancy because unintended high dosing is harder to justify. (PubMed)

14) What side effects can melatonin cause?

In adults, reported side effects are usually mild and can include:

  • next-day drowsiness
  • headache
  • dizziness

Pregnancy-specific side effect rates are not well defined, but these are common overall. (PubMed)

15) Does melatonin interact with other medications?

Yes. Melatonin is broken down by a liver enzyme called CYP1A2 (a drug-processing enzyme). Some medications can increase melatonin levels in the body, which may increase sedation or next-day drowsiness. (PMC)

16) What about breastfeeding?

Breast milk naturally contains melatonin that changes across the day (low during the day, higher at night). That means taking melatonin could change the infant’s exposure pattern, although the clinical impact is not fully clear. (PMC)

17) When is melatonin more reasonable to consider, and when is it better to avoid?

More reasonable to discuss with a clinician:

  • severe insomnia where non-drug options are not available or haven’t worked
  • strong preference to avoid sedating sleep drugs
  • short-term use at low dose (PMC)

More caution (or avoid unless clinician recommends):

  • high doses or long-term nightly use
  • uncertain supplement quality
  • interacting medications
  • complicated pregnancies where fetal growth or placental function is already a concern (PubMed)

18) What is a conservative, clinician-style step plan for pregnancy insomnia?

  1. Look for treatable causes (reflux, pain, restless legs, anxiety, frequent urination, snoring/possible sleep apnea).
  2. Use CBT-I or behavioral sleep strategies first (best evidence for pregnancy insomnia). (PMC)
  3. If still severe, discuss medication options with your clinician, including risks, benefits, and alternatives. If melatonin is chosen, aim for low dose, short duration, and higher-quality products. (PMC)