Melatonin Use During Pregnancy
Melatonin should be used with caution during pregnancy, as current evidence suggests it is probably safe but lacks robust safety data, and recent high-quality research indicates potential risks including neonatal hypoglycemia.
Current Evidence Assessment
The available evidence presents a nuanced picture. The American Academy of Sleep Medicine guideline recommends caution in women of reproductive age when using melatonin, noting concerns about potential adverse effects on reproductive function and development 1. However, this is a general precautionary statement rather than an absolute contraindication.
Safety Profile in Pregnancy
A comprehensive 2022 scoping review of human studies found that contrary to animal studies, clinical evidence suggests melatonin use during pregnancy is probably safe in humans, with no major safety concerns or adverse events reported 2. This review specifically noted that clinical trials using exogenous melatonin during pregnancy for various conditions have not demonstrated significant safety issues.
Critical Recent Finding
The most recent and highest-quality evidence raises important concerns. A 2024 double-blind, randomized, placebo-controlled trial (the MILO trial) found that babies born to mothers receiving 10 mg melatonin during labor induction were significantly more likely to require special care nursery admission, specifically for hypoglycemic monitoring (18.5% vs. 8.1%, RR 2.26) 3. This represents a clinically meaningful safety signal that cannot be ignored.
Dosing Considerations If Use Is Deemed Necessary
If melatonin is considered essential during pregnancy:
- Typical chronobiotic doses are lower than 10 mg daily 1
- Studies in fertility contexts have used 2-18 mg daily for up to six months 4
- The AASM guideline notes that short-term use of ≤10 mg/daily appears safe in healthy adults, but again emphasizes caution in women of reproductive age 1
- No consensus exists on optimal dosage or supplementation period during pregnancy 4
Clinical Decision Framework
When considering melatonin in pregnancy:
- Weigh the indication carefully - Is the sleep disorder severe enough to warrant potential fetal/neonatal risks?
- Consider non-pharmacologic alternatives first - Sleep hygiene, cognitive behavioral therapy for insomnia
- If prescribing, use the lowest effective dose - Start with 2-3 mg rather than higher doses
- Monitor for neonatal hypoglycemia - Based on the MILO trial findings, neonates exposed to melatonin may require glucose monitoring 3
- Avoid use during labor induction - The MILO trial specifically showed risks in this context 3
Important Caveats
- Melatonin is classified as a dietary supplement in the U.S., not subject to FDA medication scrutiny 1
- Purity and reliability of stated doses vary significantly between manufacturers 1
- Look for United States Pharmacopeial Convention Verified formulations for most reliable dosing 1
- Long-term effects during pregnancy remain insufficiently studied 5
- Evidence on gestational outcomes is very scarce 4
Bottom Line
Given the 2024 MILO trial findings of increased neonatal hypoglycemia risk, melatonin should only be used during pregnancy when the benefits clearly outweigh risks, at the lowest effective dose (2-3 mg), and with appropriate neonatal glucose monitoring planned. The theoretical safety suggested by earlier observational data must be balanced against this recent controlled trial evidence showing measurable neonatal harm.