Melatonin’s safety during pregnancy has not been established. While your body naturally produces melatonin and even ramps up production during pregnancy, supplemental melatonin is not regulated by the FDA as a drug, and no large-scale human trials have confirmed it is safe for pregnant women or their developing babies. Most major medical organizations recommend avoiding melatonin supplements during pregnancy due to insufficient evidence.
That said, the picture is more nuanced than a simple yes or no. Small clinical trials have used melatonin in pregnant women without reported adverse effects, and the hormone plays a critical role in healthy pregnancy. Here’s what the science actually shows.
Your Body Already Makes More Melatonin During Pregnancy
Melatonin isn’t just a sleep hormone. During pregnancy, it acts as a powerful antioxidant and anti-inflammatory agent, and the placenta actually produces its own melatonin rather than relying solely on the pineal gland in your brain. This means pregnant women have higher circulating levels of melatonin compared to non-pregnant women.
In the placenta, melatonin reduces oxidative stress by scavenging harmful molecules called free radicals. It protects the cells that form the placental barrier, supports fetal development, and helps regulate the hormonal environment needed for fetal growth. It also plays a role in modulating the immune system, which constantly adjusts throughout pregnancy to accommodate the growing fetus. In short, melatonin is deeply woven into the biology of a healthy pregnancy.
Melatonin Crosses the Placenta
Maternal melatonin passes freely through the placenta and into the fetus. Studies tracking melatonin levels in umbilical cord blood have found that fetal concentrations closely mirror the mother’s. This is actually important for the baby’s development: maternal melatonin helps set the fetal circadian clock, the internal timing system that will eventually regulate sleep-wake cycles after birth.
Research in primates has demonstrated this directly. When scientists suppressed melatonin production in pregnant capuchin monkeys, the timing of key clock genes in the fetal brain shifted. Restoring melatonin to the mother’s bloodstream reversed those changes. Beyond circadian rhythm, melatonin also appears to influence fetal brain development and protect the fetus against oxidative damage.
The fact that melatonin crosses the placenta so readily is exactly why supplemental doses raise questions. Your body carefully calibrates its own melatonin production, and adding an external dose could deliver higher-than-normal levels to the fetus at unpredictable times.
Melatonin Strengthens Uterine Contractions
One of the more concerning findings involves melatonin’s effect on uterine activity. Late in pregnancy, uterine contractions are naturally strongest at night, when melatonin levels peak. The rise in melatonin toward the end of pregnancy is thought to help trigger the contractions needed for labor.
Melatonin works in tandem with oxytocin, the hormone that drives labor contractions. Lab studies on human uterine muscle cells have shown that cells treated with both melatonin and oxytocin contract significantly more than cells treated with oxytocin alone. Melatonin also sensitizes the uterus to oxytocin by promoting the formation of gap junctions between muscle cells and activating signaling pathways that increase contractility.
This raises a theoretical concern: taking supplemental melatonin could potentially increase uterine contractions at the wrong time, particularly earlier in pregnancy. This risk has not been confirmed in human studies, but it is one reason many clinicians advise caution.
What Small Clinical Trials Have Found
No large randomized controlled trials have tested melatonin in healthy pregnant women. The human data that does exist comes from small studies focused on pregnancy complications like preeclampsia and restricted fetal growth.
A phase I clinical trial gave 20 women with early-onset preeclampsia a total of 30 mg of melatonin daily (a high dose, roughly 10 times what’s in a typical sleep supplement) from diagnosis until delivery. The trial reported no adverse events or drug reactions in the mothers, fetuses, or newborns. Another small trial gave 12 women with severe fetal growth restriction 8 mg daily from enrollment until delivery, again reporting no adverse maternal or fetal effects. A third study administered 10 mg daily to pregnant women from week 15 through week 33.
These trials are reassuring in the sense that melatonin didn’t cause obvious harm at relatively high doses. But they involved small numbers of women who were already experiencing serious complications, making it impossible to generalize to healthy pregnancies. They also weren’t designed to detect subtle effects on long-term child development.
Supplement Quality Is a Real Problem
Even if melatonin itself were proven safe during pregnancy, the supplements on store shelves present their own risks. A JAMA study analyzing 25 melatonin gummy products found that 88% were inaccurately labeled. Only 3 out of 25 products contained a melatonin quantity within 10% of what the label claimed.
Because the FDA regulates dietary supplements far less rigorously than pharmaceutical drugs, there is no guarantee that a melatonin supplement contains what it says, or that it’s free of contaminants. There is no FDA-approved dosing guidance for melatonin in any population, let alone pregnant women. This inconsistency in actual dosage makes it especially difficult to gauge what you and your baby would actually be exposed to.
Better-Studied Options for Pregnancy Insomnia
Sleep problems during pregnancy are extremely common, which is likely why so many people search for answers about melatonin. The good news is that several non-drug approaches have solid evidence behind them.
Sleep hygiene training involves establishing regular sleep and wake times, avoiding naps and caffeine, minimizing fluid intake before bed to reduce nighttime bathroom trips, and using pillows to manage physical discomfort. Studies in third-trimester women have found that structured sleep hygiene education improves sleep quality.
Relaxation exercises done before bed, such as listening to a guided relaxation recording, have shown benefits in the third trimester. Music listening, specifically 30 minutes of calming music at bedtime, has improved sleep quality in studies of women between 18 and 34 weeks. Physical exercise programs, including water-based exercise two to three times per week, have also been effective when started in the second trimester.
Cognitive behavioral therapy for insomnia is considered a first-line treatment and works by reshaping the thought patterns and behaviors that keep you awake. Acupressure, prenatal yoga, and meditation have shown promise in smaller studies, though the evidence is less robust. When insomnia occurs alongside depression, a combination of partial sleep deprivation and light therapy has shown early benefits in a small trial of 12 pregnant women.
For women who need medication, certain antihistamines are widely used during pregnancy for nausea and allergy symptoms and have sedating effects. These should still be discussed with a provider, but they have a much longer track record of use in pregnancy than melatonin supplements do.