If you’re trying to get pregnant, you’ve probably given some thought to questions of diet and exercise: what supplements do you need to start taking? Is it okay to drink alcohol while you’re trying to conceive? Do you need to change your exercise routine?
But here are a few questions you’ve probably never considered:
- Your nighttime reading habits
- The thickness of your bedroom curtains
- The location of windows in your workplace
If you’re thinking about nutrition and exercise while trying to get pregnant, you should be thinking about the light you’re exposed to throughout the day, because research suggests it has at least as big of an impact on fertility.
The Profound Impact of Light on Your Body
It’s long been understood that exposure to light is the catalyst for hormonal responses that influence how awake you feel. But more recently, research has begun to uncover that daily patterns of light exposure can have wide-ranging health impacts, influencing your mood, your weight, your risk level for certain types of cancers1, and your reproductive health2.
Light is what keeps our bodies in sync with the 24-hour day. A century ago, when people spent more time outdoors during the day and were exposed to less artificial light at night, they tended to get more sleep. In 1910, average sleep duration was about nine hours, and today, it’s down to 7.53.
If you’ve ever gone camping, you’ve experienced this kind of circadian rhythm firsthand. Out in the woods, protected from the effects of artificial light, people tend to fall asleep soon after the sun sets, and wake soon after it rises.
Why does this happen? Think about how it feels when you first open the curtains in the morning, the way the light shocks you awake. That’s the feeling of your body suppressing melatonin production in response to daylight, causing you to feel more alert. The opposite happens when you’re exposed to darkness—the absence of light signals your body to increase melatonin production, which makes you feel sleepy.
For most of human history, we experienced a long, uninterrupted period of light followed by a long, uninterrupted period of darkness. Today, we spend our days indoors and our nights in artificially lit rooms staring at bright screens. Unsurprisingly, this disturbs our normal sleep patterns.
Research has shown that short-wavelength blue light—the kind that’s emitted from our mobile devices—is a particularly potent melatonin suppressor. In a 2014 study, participants who read on light-emitting devices took longer to fall asleep, had less REM sleep, felt more alert at bedtime, and felt sleepier in the morning than participants who read printed books.4 This, combined with the fact that people tend to use their devices before bed, makes for a strong sleep-killing cocktail.
Why Sleep Matters for Fertility
If using mobile devices at night causes you to go to bed later and sleep less, it could impact your fertility indirectly by causing you to feel more stressed from sleep deprivation5. But mobile devices can have a direct impact on fertility as well. Here’s why:
Melatonin is the hormone that makes us feel sleepy, but that’s not all it does. It also plays an important role in reproductive health, protecting eggs from free-radical damage during ovulation. The study of circadian rhythms and fertility is still relatively new, but research has shown that irregular sleep patterns can have a variety of reproductive impacts, including:
- increased risk of miscarriage
- low birth weight
- irregular menstrual cycles
- lower rate of pregnancy
- higher rates of stillbirth
None of this is surprising when you consider that the 28-day menstrual cycle follows a pattern based on the 29-day lunar cycle. The moon’s light ebbs and flows over the course of the month, with the brightest days around the full moon. In 1990, Psychiatry Research published a study reporting that women with long and irregular menstrual cycles who used light exposure that mimicked moonlight could shorten and regular their cycles.
More recently, scientists have focused on how daylight exposure impacts the menstrual cycle. A 2007 Psychiatry Research study reported that women receiving light therapy for seasonal affective disorder started their periods 1.2 days earlier on average.
What You Can Do
Here’s how to make the science of light and darkness work for you and your fertility:
Seek out light in the morning. Go outside in the morning, or sit near a window with abundant light. It takes about 10 minutes to fully suppress melatonin, so make sure you get at least that much daylight time soon after waking.
Seek out total darkness at night. Make sure your bedroom is really dark. Throw a t-shirt over clocks, charging devices, and other things that might emit light. Invest in blackout curtains.
Get sunlight during the day. There’s some evidence that melatonin may act directly on reproductive tissues, making women more fertile during times of year when there is maximum daylight. Try to get outside during the brightest part of the day.
Maintain a regular schedule. When you’re trying to conceive, be extra vigilant about maintaining a regular schedule, minimizing frequent travel that could give you jet lag and throw off your internal clock.
Block blue light. Blue light—the kind that emanates from your iPhone screen—delays the flow of melatonin. Try to put your devices away a few hours before bed.