Is melatonin safe to use during pregnancy for treating insomnia?

Melatonin Use During Pregnancy for Insomnia

Melatonin is likely safe for short-term use during pregnancy based on available human data, though it is not formally recommended as first-line therapy for insomnia due to insufficient evidence of efficacy for this specific indication.

Current Evidence on Safety in Pregnancy

• A scoping review of human studies found that clinical trials using exogenous melatonin during pregnancy have not suggested major safety concerns or adverse events, contrary to concerns raised by animal studies 1
• Approximately 4% of pregnant women use melatonin according to large health administrative databases, indicating widespread real-world use 1
• No randomized controlled trials have specifically examined melatonin's efficacy and safety for treating insomnia during pregnancy—insomnia was not the primary outcome in any included human studies 1, 2
• Maternal melatonin easily crosses the placenta and provides photoperiodic signals to the fetus, with physiological roles in pregnancy and fetal development 3, 4

Efficacy Concerns for Insomnia Treatment

• The American Academy of Sleep Medicine recommends against using melatonin for sleep onset or sleep maintenance insomnia in adults with primary insomnia due to weak evidence showing only minimal benefit: approximately 9 minutes reduction in sleep latency with small improvements in sleep quality 5, 6
• Meta-analyses demonstrate melatonin has small effects on sleep latency with little effect on wake after sleep onset or total sleep time 6
• The overall quality of evidence for melatonin in insomnia is very low due to heterogeneity, imprecision, and potential publication bias 6

Safety Considerations Specific to Pregnancy

• A 1997 review noted potential concerns including inhibition of reproductive function, delayed puberty timing, and influence on fetal circadian development when taken during pregnancy and lactation, though these were based primarily on animal data 7
• The National Academy of Sciences recommended caution in women of reproductive age when using melatonin, though this was based on limited data 6
• Common mild side effects include morning drowsiness, headache, gastrointestinal upset, and dizziness, with no serious adverse reactions documented across studies 5
• Melatonin has been associated with increased depressive symptoms in some patients and may impair glucose tolerance after acute administration 6, 5
• Use caution in patients taking warfarin or with epilepsy 6, 5

Practical Clinical Algorithm

Step 1: Optimize Non-Pharmacologic Approaches First

• Implement sleep hygiene: consistent bedtime/wake time, avoid caffeine ≥6 hours before bed, limit evening screen time, optimize bedroom environment 8
• These behavioral modifications are safe in pregnancy and should be the foundation of treatment 8

Step 2: If Melatonin Is Considered

• Choose United States Pharmacopeial Convention (USP) Verified formulations to ensure purity and reliable dosing, as melatonin is regulated as a dietary supplement with variable quality 6, 5, 9
• Consider 2-3 mg of immediate-release or prolonged-release melatonin taken 1-2 hours before bedtime 5, 9
• Limit use to the shortest duration necessary given lack of long-term safety data in pregnancy 1, 2
• Monitor for side effects including morning drowsiness, mood changes, and gastrointestinal symptoms 5

Step 3: Reassess After 1-2 Weeks

• If no improvement in sleep onset or maintenance, discontinue melatonin given its limited efficacy for primary insomnia 5, 6
• Evaluate for underlying sleep disorders (sleep apnea, restless legs syndrome) that may complicate pregnancy 8

Critical Pitfalls to Avoid

• Do not use melatonin as first-line therapy when behavioral sleep interventions have not been attempted, as sleep hygiene and stimulus control are safer and more appropriate in pregnancy 5, 8
• Avoid doses >10 mg due to potential receptor desensitization and lack of additional benefit 5
• Do not use antihistamines (diphenhydramine) or trazodone for insomnia in pregnancy, as these have even less evidence for efficacy and safety concerns including anticholinergic effects and daytime sedation 5, 6
• Recognize that melatonin's primary evidence base is for circadian rhythm disorders (delayed sleep-wake phase disorder), not primary insomnia 5, 6

Bottom Line

While human data suggest melatonin is probably safe during pregnancy, its efficacy for treating insomnia is marginal at best. Behavioral sleep interventions should be the primary approach, with melatonin reserved for short-term use only after non-pharmacologic measures have failed, using USP-verified formulations at the lowest effective dose (2-3 mg).