Many people take melatonin as a supplement to improve sleep quality. However, if you are pregnant and experiencing sleeping difficulty, you may be wondering whether it is safe to take melatonin while pregnant.
This article answers your questions about whether melatonin is safe for pregnancy. We also answer your questions about:
How long it stays in your system
What is melatonin?
Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine hormone produced naturally by the pineal gland located in the brain. It is available over the counter (OTC) in the U.S. and Canada as a sleep aid for the short-term management of sleep-wake cycle-related issues, including jet lag, shift work sleep disorder, and delayed sleep-wake phase disorder.
OTC melatonin may be administered sublingually (placed under the tongue) or as a tablet for swallowing.
Melatonin plays a role in regulating the sleep-wake cycle in the 24-hour circadian rhythm and adjustments due to seasonal variations in daylength (Zisapel, Brown et al., Wehr, Adamsson et al.).
Circadian rhythms (also known as circadian cycles) are cyclical variations in biological systems that are adaptive responses to the cycle of day and night. Many organisms exhibit a well-defined pattern of changes, variations, or transitions of function that sync with diurnal rhtythms.
The best-known circadian rhythm in higher animals is the sleep-wake cycle associated with day and night and its seasonal photoperiod variations. Other biological functions associated with circadian rhythms include blood pressure regulation (Mozdzan et al., Douma et al.), body temperature regulation (Cagnacci et al., Lok et al.), regulation of reproductive function in humans (Reiter et al., Olcese), and the control of seasonal reproductive cycles in some mammalian species (Voordouw et al.)
Scientists also use the term “biological clock” or “circadian clock” to refer to the internal systems that regulate circadian rhythms (Copertaro and Bracci, Farhud and Aryan).
Melatonin is one of the hormones that play a role in the “biological clock.”
Can pregnant women take melatonin?
Melatonin is produced by the pineal gland in pregnant and nonpregnant women. Studies that showed that levels of the hormone rise during pregnancy and fall after birth led to the suggestion that it plays an important role in pregnancy and parturition (the act of giving birth).
Reiter and colleagues suggested that the tendency for parturition to occur at night may be due to synergy between melatonin and the birth hormone oxytocin.
Although there are indications that the hormone may play a protective role during pregnancy and childbirth, not enough studies have been done to recommend its use as a dietary supplement for pregnant and breastfeeding women.
Voiculescu and associates concluded that despite its potential role in improving reproductive function, more research needs to be done to establish its safety and efficacy. Seko and associates also concluded that more studies were needed to establish the safety of of the hormone for pregnant and nursing women.
We also previously reported that research studies have not established the safety of the adaptogen herb ashwagandha in pregnancy and breastfeeding. Always consult your doctor if you want to take any supplement during pregnancy.
Melatonin isn’t recommended in pregnancy, but studies suggest benefits
Although experts don’t recommend melatonin supplementation during pregnancy and breastfeeding, recent studies suggest it may promote maternal and offspring health.
Melatonin supplementation during pregnancy and lactation may help prevent cardiovascular and neurological diseases later in life (Hsu and associates).
Tamura and colleagues reported that supplementation may help improve ovarian function and oocyte quality and provide new therapies for ovarian diseases.
According to Voiculescu and associates, melatonin regulates circadian rhythms, induces sleep, has antioxidant, anticarcinogenic, and neuroprotective properties. It also plays a role in fetal development and low levels may lead to reproductive dysfunction. The embryo and fetus have melatonin receptors and depend on maternal production through the placenta.
Melatonin plays a protective role in pregnancy from oocyte stage to parturition, according to Voiculescu and associates. Levels of the hormone increase after 24 weeks of pregnancy and reach high levels after 32 weeks.
Ejaz and colleagues also suggested that the placenta may produce melatonin during pregnancy. The authors noted that maternal serum melatonin increases in pregnancy and falls immediately after parturition. They concluded that the hormone may play essential physiological roles during pregnancy.
Melatonin promotes placental and uterine health by maintaining uterine homeostasis (Almeida Chuffa et al.). According to the researchers, low levels of the hormone are associated with low implantation rates, difficulties maintaining pregnancy, recurrent spontaneous abortion, and maternal/fetal disturbances. They proposed that melatonin replacement may help restore normal function of the uterus and placenta by alleviating oxidative stress and improving vascular function at the uterine–placental interface.
An animal study (mice) concluded that the hormone may help prevent preterm labor and increase offspring survival (Rubio et al.). Another study proposed that as a powerful antioxidant, it may mitigate morbidity and mortality associated with fetal growth restriction (Alers et al.).
Reiter and co-workers concluded that melatonin plays an essential role in fetal maturation and placental/uterine homeostasis. The researchers suggested that due to its potent antioxidant activity and low toxicity, it may help in treating preeclampsia (complications due to high blood pressure and proteinuria during pregnancy), intrauterine growth restriction, placental, and fetal ischemia (reduced flow of blood to the fetus).
Mingzhi Zhao and associates also concluded that melatonin may play a role in reducing the risk of preeclampsia.
The hormone improves placental efficiency and birth weight in undernourished pregnant women, according to Richter et al. The authors reported that studies show that it improves outcomes in pregnancies complicated by undernutrition.
However, some studies suggested that melatonin may not be safe during pregnancy and breastfeeding. Singh and associates reported that it negatively affected maternal weight, baby birth weight, and mortality in rats.
Melatonin sleep benefits in nonpregnant women
Although experts don’t recommend melatonin during pregnancy, research studies support its use for the short-term management of sleep-wake cycle-related disorders in nonpregnant and non-breastfeeding women. Multiple studies indicate that short-term use has a beneficial effect on sleep quality.
Brzezinski and colleagues conducted a study to determine the effect of “exogenous melatonin” (melatonin taken as a supplement in addition to that naturally produced) on sleep. The researchers measured the effect of the hormone on the following measures of sleep quality: Sleep onset latency, total sleep duration, and sleep efficiency.
They found that:
- Melatonin significantly reduced sleep onset latency (sleep onset latency is the time it takes to fall asleep).
- It improved sleep efficiency (sleep efficiency, according to Deepak Shrivastava et al., is the “percentage of total time in bed spent in sleep”).
- It increased total sleep duration.
A review by Costello and colleagues concluded that melatonin may play a role in managing sleep disorders, improving sleep onset latency, and sleep efficacy. Sletten and associates also concluded that taking the supplement before bedtime improved objective and subjective measures of sleep quality.
How does melatonin work?
According to Johns Hopkins sleep expert Luis F. Buenaver, melatonin levels rise about two hours before bedtime. However, it does not make you sleep. It only enables a state of calmness and relaxation that promotes sleep.
A group of neurons located in the hypothalamus, known as the suprachiasmatic nucleus (SCN), has been identified as the brain’s “circadian clock.” Neurotransmitter-mediated signals to the pineal gland (Ma and Morrison, Reghunandanan) from the SCN trigger increased production of melatonin in the night. But when exposed to light during the day, the retina signals to the SCN, which in turn signals to the pineal gland to lower production so that you can stay alert and wakeful.
Most people naturally produce enough of the hormone to regulate their sleep-wake cycle, but some people may require supplementation on a short-term basis to manage issues such as insomnia or jet lag.
When to take melatonin?
Buenaver advised nonpregnant and non-breastfeeding women who need melatonin for insomnia to take only about 1 to 3mg two hours before bedtime. In the case of jet lag, it is best to start supplementation a few days before the trip.
Your doctor may prescribe the hormone for sleep-cyle-related disorders, such as jet lag, shift work sleep disorder, short-term management of insomnia, and delayed sleep-wake phase disorder (DSWPD).
Some surgeons also prescribe it to reduce anxiety before and after surgery.
Cardinali and associates suggested that melatonin may play a role in treating mild cognitive impairment (MCI) and improving sleep quality in Alzheimer’s disease (AD) patients (Wade et al.). It may also play a role in treating sleep disorders in children with developmental disabilities (Schwichtenberg and Mallow), sleep onset insomnia in children with autism spectrum disorder (Goldman et al.), and circadian desynchrony in the blind (Lockley et al.).
Melatonin is considered safe at low doses for short-term use by women who aren’t pregnant or breastfeeding. The side effects are usually mild. Andersen and associates reported that although studies did not suggest that supplementation has any serious adverse effects, there was a need for further investigation, especially regarding its use for treating sleep disorders in children and adolescents.
According to Andersen and associates, mild but rare side effects include:
- Daytime sleepiness
Other rare side-effects or adverse events due to melatonin use include:
- Abdominal pain
- Abnormal dreams
- Dyspepsia (discomfort, pain, bloating in the upper abdomen associated with indigestion)
- Mouth ulcers
- Dry mouth
- Hyperbilirubinaemia (too much bilirubin in the blood; bilirubin is a substance formed when red blood cells break down)
- Dermatitis (irritation or inflammation of the skin)
- Night sweats
- Pruritus (itching)
- Dry skin
- Psychomotor hyperactivity (a symptom of mood disorder characterized by unintentional repititive, purposeless movements and behaviors)
- Pain in the extremities
- Symptoms of the menopause
- Asthenia (weakness)
- Chest pain
- Glycosuria (sugar in the urine)
- Proteinuria (protein in the urine)
- Abnormal liver function tests
- Weight gain
Side effects may also include:
- Mood swings
- Feeling hungover
How long for melatonin to work?
When administered by the sublingual route (placed under the tongue to dissolve), melatonin is absorbed very quickly into the bloodstream.
The sublingual mucosa on the ventral (underside) surface of the tongue (Maheshwari and Tekade) is well supplied with blood vessels. Pharmaceutical preparations dissolved under the tongue pass straight into the systemic circulation, facilitating a rapid onset of action (Hua et al.).
Medication supplied through the sublingual route enters the systemic circulation via the sublingual venous drainage and the superior vena cava (Hua et al.). The superior vena cava is the large vein that carries blood from the head, neck, arms, and chest to the heart.
Melatonin is also efficiently absorbed into the circulation through the digestive tract, with most of the absorption taking place in the rectum and ileum (Tran et al.)
Aldhous and associates reported that gelatine capsules and corn oil preparation delivered peak plasma concentrations about 30 to 60 min after ingestion regardless of the nutritional status of the subject.
How long does melatonin stay in your system?
Aldhous and associates also reported that plasma melatonin remained at or above endogenous (natural) night-time levels for 3-4 hours after ingestion. The mean half-life was 0.54 to 0.67 h (32-40 minutes).
The researchers (Aldhous et al.) found that slow-release preparations extended the duration of high plasma concentrations for 5-7 hours after ingestion. However, the timing of peak plasma concentrations depended on the subject’s nutritional status.
Does melatonin cancel out birth control?
Research is ongoing on the possible interactions between melatonin and birth control. But the results from some studies appear conflicting. While some studies suggested that melatonin may play a role in birth control, others reported it boosts fertility.
Presl reported that plasma levels of melatonin fluctuate with the phase of menstruation. It peaks at the beginning of the menstrual cycle and decreases around ovulation. The researcher suggested that the hormone may have utility as an oral contraceptive either alone or combined with norethindrone (a form of progesterone).
However, a study by Espino and colleagues appeared to contradict Presl’s conclusion. The researchers reported that melatonin may improve fertility due to its powerful antioxidant properties.
Song and associates also reported that the hormone may improve age-related decline in fertility and reduce ovarian aging in mice by countering ovarian mitochondrial oxidative stress.
Studies have shown that some birth control medication may boost melatonin. Thus, taking melatonin for any purpose, including as a sleep aid while taking birth control pills, may cause excessively high levels.
Bezerra and colleagues noted that progesterone — a steroid hormone produced by the corpus luteum in the ovary that helps regulate the menstrual cycle and maintain pregnancy — also improves sleep quality (Caufriez et al.) partly by modulating melatonin secretion. They suggested that hormonal contraceptives may play a role in treating insomnia by potentiating the sleep-promoting effects of melatonin supplements.
It is advisable to talk to your doctor if you want to take melatonin supplements while on birth control.
A note to our readers
This article is meant only for informational purposes. It is not in place of professional medical advice.
Although some studies suggest that melatonin supplementation may have beneficial effects during pregnancy, there isn’t enough research to establish its safety.
If you are pregnant and experiencing sleep disturbances, we recommend that you consult your doctor on the best treatment for sleep-related issues during pregnancy.
To protect the health of your unborn child, you need to talk to a qualified healthcare professional before taking any medication or supplement during pregnancy.