If you’ve been trying to improve your egg quality, you’ve probably heard me talk about sleep. Sleep is one of the foundations I come back to again and again because it affects blood sugar, inflammation, mitochondrial health, hormone signaling, nervous system regulation, and the environment your eggs are developing in. But there’s another piece of sleep and fertility that gets far less attention: light and darkness.
Your ovaries have a circadian clock, and that clock is heavily influenced by light exposure. Bright lights at night, screens in bed, and light coming through your bedroom window can all affect the signals that tell your body it’s nighttime. Darkness helps support melatonin production, and melatonin isn’t just a sleep hormone. It’s also found inside the ovarian follicles surrounding developing eggs, where it helps protect them from oxidative stress. In this episode, I’m breaking down why your ovaries care about darkness, how circadian rhythm influences reproductive health, what the research tells us about melatonin and egg quality, and five practical changes you can start making tonight.
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“The goal isn’t to replace darkness with a pill.”
What You’ll Learn:
Why your ovaries have their own circadian clock
How light exposure influences reproductive hormones and ovulation
Why darkness and melatonin matter for egg quality
How oxidative stress affects developing eggs
What research shows about sleep, circadian disruption, and IVF outcomes
Five practical ways to improve your light exposure and circadian rhythm
When melatonin supplementation may support fertility and IVF
Why egg quality depends on more than supplements alone
Why the 90 days before ovulation can be such an important window for fertility support
“Darkness might be one of the most overlooked tools for egg quality.”
Links Mentioned:
Get a copy of my Preconception Checklist
Get my FREE Fertility Meal Plan
References:
Caetano G, et al. Impact of sleep on female and male reproductive functions: a systematic review. Fertility and Sterility. 2021.
Huang Y, et al. Sleep disturbances and assisted reproduction outcomes in women undergoing IVF/ICSI: a systematic review and meta-analysis. BMC Pregnancy and Childbirth. 2026.
Wang H, et al. Sleep disturbances and female infertility: a systematic review. BMC Women's Health. 2024.
Willis SK, et al. Impact of sleep patterns upon female neuroendocrinology and reproductive outcomes: a comprehensive review. Reproductive BioMedicine Online. 2022.
Sen A, et al. Impact of circadian rhythms on female reproduction and infertility treatment success. Current Opinion in Endocrinology, Diabetes and Obesity. 2019.
Mejlhede MAB, et al. Oral melatonin supplementation during in vitro fertilization treatment: a systematic PRISMA review and meta-analysis of randomized controlled trials. Gynecological Endocrinology. 2021.
Tang H, et al. Melatonin supplementation and outcomes of assisted reproductive technology: a systematic review and meta-analysis. BMC Pregnancy and Childbirth. 2025.
Tamura H, et al. Oxidative stress impairs oocyte quality and melatonin protects oocytes from free radical damage and improves fertilization rate. Journal of Pineal Research. 2008.
Nishihara T, et al. Oral melatonin supplementation improves oocyte and embryo quality in women undergoing in vitro fertilization-embryo transfer. Gynecological Endocrinology. 2014.
Espino J, et al. Melatonin in Assisted Reproductive Technology: A Pilot Double-Blind Randomized Placebo-Controlled Clinical Trial. Frontiers in Endocrinology. 2018.
“Your ovaries are also paying attention to light and darkness.”
Transcript:
Darkness might be one of the most overlooked tools for egg quality.
If you've listened to this podcast for any length of time, you've heard me talk about sleep and egg quality. Sleep is one of the foundations I come back to again and again because it affects blood sugar and inflammation, mitochondrial health, hormone signaling, nervous system regulation, and the environment your eggs are developing in.
But today I want to get even more specific.
It isn't only how many hours you sleep or how rested you feel. Your ovaries are also paying attention to light and darkness.
Your reproductive system runs on a circadian clock, and that clock is heavily influenced by light exposure.
So what happens when nighttime isn't actually dark?
When you're under bright overhead lights until 10 o'clock or later, when your phone is inches from your face in bed, or when there is light coming through your bedroom window all night long, that matters.
Darkness is one of the primary signals telling your body to release melatonin.
Melatonin isn't just a sleep hormone. It is also found inside your ovarian follicles, where it helps protect developing eggs from oxidative stress.
Today we're talking about the piece of sleep and egg quality that gets far less attention: darkness.
We'll look at why your ovaries care about it, how your circadian clock helps regulate ovulation, what the research tells us about melatonin and oocyte quality, and five practical changes you can start making tonight.
Your Ovaries Have a Circadian Clock:
Your ovaries actually have a clock.
Your circadian rhythm is not just about whether you feel sleepy at 10 o'clock at night. We have a central clock in the brain, but we also have clock machinery throughout the whole body, including within reproductive tissues.
Reproduction is incredibly time-sensitive.
The hypothalamic-pituitary-ovarian axis depends on appropriately timed signaling between hormones like LH, FSH, estrogen, and progesterone. That signaling helps coordinate follicular development, the LH surge, ovulation, and the reproductive cycle as a whole.
This is one reason I want you to stop separating sleep from fertility.
Sleep isn't just recovery after everything else you did that day.
It is part of your fertility biology.
Research has linked circadian disruption, short sleep, poor sleep quality, and night shift work with changes in reproductive function. In some studies, we also see poorer fertility and assisted reproduction outcomes associated with these factors.
Women struggling with infertility also appear to experience sleep disturbances more frequently.
That doesn't mean poor sleep caused someone's infertility. We have to be careful with that distinction because infertility itself is stressful.
Fertility treatments can disrupt sleep too, and hormonal and metabolic issues can also affect sleep.
There are relationships going in both directions, and that's really important to know.
We do have enough evidence at this point to say that sleep and circadian health deserve a seat at the preconception table.
Why Light Exposure Matters:
Light is one of the main signals setting the clock in our body and our reproductive system as a whole.
Your body needs contrast:
Bright light during the day.
Darkness at night.
That sounds almost ridiculously simple, right?
But think about how most of us live now.
We wake up inside. We work inside. We barely see natural daylight.
Then nighttime comes and suddenly our environment is brighter, with overhead lights, TVs, screens, and phones.
We're scrolling through our phones in bed.
There are little lights coming from chargers, clocks, electronics, and whatever else is glowing around the bedroom.
From a circadian standpoint, that is a very different environment from the one human biology developed around.
Your brain uses light as information.
Light tells your body it's daytime.
Darkness tells your body it's nighttime.
And one of the hormones responding to that signal is melatonin.
Melatonin and Egg Quality:
Melatonin is much more than a sleep hormone.
This is where the conversation gets really interesting for egg quality.
Most people think of melatonin as a supplement that you take when you can't sleep, but it's so much more than that.
Melatonin production rises under dark conditions, and light exposure at night can actually suppress that signal.
Melatonin isn't only relevant to your brain. It is also found in follicular fluid, which surrounds the developing oocyte, or egg.
One of its important jobs within that follicular fluid appears to be antioxidant protection.
Think about what an egg is doing during follicular development.
It requires a tremendous amount of energy.
The mitochondria are involved, and there are actually 10 times more mitochondria involved in these cells than anywhere else in the body, giving you an idea of how much energy is required.
Reactive oxygen species are also produced.
We need some oxidative signaling. We don't want zero oxidative stress.
But excessive oxidative stress can damage cellular structures, mitochondrial function, and DNA.
The follicular environment needs antioxidant defenses to help maintain that balance.
Melatonin appears to be one of the pieces of that system.
This is where we start connecting your nighttime environment with ovarian biology.
We have research showing relationships between melatonin within the follicular environment, oxidative stress, oocyte maturation, fertilization, and embryo development.
There are also clinical trials looking at supplemental melatonin during IVF.
A 2021 meta-analysis of randomized controlled trials found that women taking oral melatonin during IVF had a significantly greater number of mature oocytes, or eggs.
A newer meta-analysis has also found improvements in mature oocytes, fertilization rates, and top-quality embryos with melatonin supplementation.
That doesn't mean everyone trying to get pregnant should immediately start taking melatonin.
There's an important distinction here.
A supplement is not the same thing as restoring your circadian rhythm.
You can't scroll under bright lights until midnight, sleep for six hours, wake up at a different time every day, and expect a melatonin supplement to erase all of those other signals.
The supplement may absolutely have a supportive role, but it isn't a band-aid or a fix-all.
We want to build the biology first.
Sleep and IVF Outcomes:
Let's talk a little bit more about sleep and IVF outcomes.
We have a growing body of research looking specifically at sleep and fertility treatment.
A recent systematic review found that women with infertility generally reported poorer sleep quality and more evening wakeups.
Poor sleep quality and extreme sleep durations have also been associated with outcomes including fewer retrieved eggs, poorer embryo quality, and lower fertilization rates.
We want more evidence on all of this, and we're continuing to gather this insightful data.
A very recent 2026 meta-analysis looked at almost 10,000 women undergoing IVF and found that sleep-disordered breathing was associated with substantially lower odds of clinical pregnancy and live birth as well.
It doesn't prove that fixing sleep guarantees better IVF outcomes.
But it does tell us something really important.
Sleep is not fluff.
It is not the thing we work on after we've brought in every fertility supplement available.
It's not the last thing on our list.
It is physiology.
And this is exactly why my approach to egg quality is so much bigger than taking an egg quality supplement stack.
Egg Quality Is About the Whole Environment:
Egg quality reflects the environment an egg is developing within.
We want adequate nutrients, stable glucose availability, healthy mitochondrial function, appropriate thyroid signaling, low enough inflammatory and oxidative burden, good blood flow, and a nervous system and circadian environment that actually communicate safety, nourishment, and appropriate timing.
Your body needs so much energy to support reproduction, but it also needs to know when to use that energy, when to repair, and when to reproduce.
So what can you do?
There are five areas that I would start with, and you can start on these as early as tonight.
Get Bright Light Early in Your Day:
This conversation isn't only about avoiding light.
We want stronger circadian signals.
Get outside after waking, ideally within 30 minutes of waking if you can, before any screen time.
Natural outdoor light gives your brain a powerful daytime signal and helps anchor your circadian rhythm.
It makes the contrast between day and night stronger.
Create a Consistent Sleep Opportunity:
Give yourself a consistent sleep opportunity.
Aim for at least seven hours, ideally closer to nine, and keep your bedtime and wake time relatively consistent.
You don't want to become obsessive about going to bed at exactly 9:47 every night.
We're looking for rhythm.
If you're sleeping from 10 p.m. to 6 a.m. Monday through Friday, and then 1 a.m. to 9 a.m. every weekend, your clock is constantly having to adjust.
Consistency really does matter for our circadian rhythm.
Dim Your Environment at Night:
Start lowering light exposure about two hours before bed.
Dim your overhead lights and use warmer, lower lighting.
Get off bright screens, ideally at least an hour before bed, and keep the bedroom dark.
Blackout curtains can be incredibly helpful if outdoor light comes into your room.
I want your nighttime environment actually communicating nighttime.
And if you're unsure of how dark your room needs to be, a good rule of thumb is to hold your hand in front of your face, about six inches away.
You should not be able to see it.
It should be that dark within your room.
Pay Attention to Shift Work:
Pay attention to shift work.
If you work nights or rotating shifts, this does not mean you can't have healthy fertility.
That's not what I'm saying.
But circadian disruption becomes something I would intentionally address during your preconception time period.
If you have control over your schedule, minimizing rapidly rotating day and night schedules during the three to four months before conception or before an egg retrieval is absolutely worth discussing.
If you don't have control over your schedule, then we work with what you do have control over:
Your light environment.
Your sleep opportunity.
Your meal timing.
Your recovery.
Your nutrient status.
Your stress load.
You can also consider using melatonin when you need to sleep during the day, as well as creating as much darkness as possible within your sleep space.
We don't need perfection to improve biology.
But these strategies can make a big difference in helping you get the outcomes you're looking for.
Consider Whether Melatonin Makes Sense for You:
The fifth strategy is to consider whether melatonin supplementation actually makes sense for you.
There is legitimate research here, particularly in IVF.
Three milligrams per day has been studied in several fertility trials, including research in women with previous poor fertilization and diminished ovarian reserve.
More recent meta-analysis suggests that melatonin may improve intermediate ART outcomes like mature oocyte numbers, fertilization, and embryo quality.
The evidence for live birth is still not convincing, but we see better outcomes initially.
And I personally think that this goes back to the entire environment.
Melatonin is a really important piece of the puzzle, but it's not the whole puzzle.
So don't look at melatonin as an automatic fertility supplement.
If you are preparing for IVF and have circadian disruption, or your practitioner believes you may benefit from it, it's reasonable to have that conversation.
Your medication history, health history, sleep issues, and fertility treatment plan all make a difference as to whether it's going to help you.
Darkness Is Not Something You Can Replace With a Pill:
I really want to emphasize this again.
The goal isn't to replace darkness with a pill.
Melatonin supplementation can potentially support the system and the environment that you are creating.
It does not replace the habits that regulate that system.
Let's step back and look at the bigger picture.
If you've been trying to improve your egg quality, I want you to think beyond your supplement cabinet.
What does your body experience over a 24-hour day?
When does it see sunlight?
When does it see darkness?
When does it eat?
When does it sleep?
Is there rhythm?
Is there enough energy coming in?
Is there enough time to recover?
Because follicles don't develop in isolation.
Your ovaries are responding to the same metabolic, inflammatory, nutritional, hormonal, and circadian environment as the whole rest of you.
Why the 90 Days Before Ovulation Matter:
Egg development takes time.
It takes at least a 90-day period.
We have the most influence over that 90-day time period before ovulation occurs.
This is why I care so much about the three to four months before conception or fertility treatment.
You have an opportunity during that window to change the environment those developing follicles are exposed to.
Not perfectly, but very meaningfully.
Start Tonight:
Tonight, don't make this complicated.
Dim the lights.
Put your phone away earlier.
Make your bedtime genuinely dark.
Your bedroom should be very dark. You shouldn't be able to see your hand within six inches of your face.
Give yourself enough time to sleep.
And tomorrow morning, get outside.
Get that sunlight or skylight in your eyes.
It doesn't have to be sunny. Even if it's overcast, it does make a difference.
These things sound almost too simple compared with the complicated world of fertility treatment.
But simple doesn't mean insignificant.
Sleep and circadian rhythm are foundational biology, and foundations are exactly where I want to start.
And if you're listening to this thinking, "Okay, Brooke, but sleep is definitely not the only thing I need to work on," you're absolutely right.
I have a complete preconception checklist that walks you through the bigger picture and the areas I think deserve attention before pregnancy or fertility treatment.
And if you want more of these deeper dives into research and conventional fertility conversations, because there are a lot of gaps in those conventional fertility approaches, follow along with me on Substack.
Because fertility isn't about finding one magic supplement.
We know that doesn't exist.
It's about understanding what your body needs to support reproduction and then systematically building that environment.
Hope to see you next week.