Could your evening screen time be sending signals to your baby?

The surprising science of light, pregnancy and your baby’s first biological clock

When I started writing The Light Fix, I already had a stack of studies showing how light, both natural and artificial, affects our sleep, metabolism and overall hormonal health. What I didn’t expect, was to find myself completely immersed in research on pregnancy, babies, childhood development and our younger years.

The more I read, the more I realised that the story of light doesn’t begin when we’re born, but long before our first breath.

In fact, my chapter A Lifetime of Light now begins in utero because of some of the studies I’m about to share with you. They completely changed the way I think about when our circadian biology really begins. They also beautifully reinforce something I say to every woman who comes to me for fertility support and is hoping to have a baby: “the work starts before you even conceive”. I always tell them to think of it like preparing your home before the most special guest arrives. You wouldn’t wait until someone knocked on the door before you started cleaning, decorating and getting everything ready. Your body and future baby deserves the same care.

That means eating like a warrior, sleeping like a baby (cos let’s face it, you won’t be doing that again for a while) filling any nutritional gaps, getting your gut in good shape, reducing stress and building a body that’s ready to nurture new life. It all matters.

What I hadn’t fully appreciated until I read these papers, was that your light environment matters too. How much daylight you see, how late you’re watching television + scrolling on your phone at night etc.. These seemingly small habits may be sending signals long before your baby is even born.

Before I dive into the findings, I should probably explain why I’m sharing these studies.

Writing The Light Fix has become a bit of an obsession. Every week, I come across a paper that makes me stop, rethink what I thought I knew, or simply sit back and think, “wow.” Rather than keeping these discoveries to myself, I thought I’d bring you along for the journey.

So, each week I’ll share the science that I genuinely believe belongs in the book - research that helps make an important point or reveals something we need to understand. I’ll explain what the researchers actually found and show you how it fits into the bigger story I’m uncovering as I write the book.

I’d also love your help. One of my biggest goals with The Light Fix is to write a book that’s grounded in robust science but accessible enough that both my mother and someone who’s never once thought about the health effects of light could pick it up, enjoy it, and come away with practical changes they could start making that very day. I want it to be fascinating but easy to understand and, above all, genuinely useful.

So, as you read these posts, I’d really love your feedback. Does this kind of science interest you? Does it make sense? And is it the sort of thing you’d want to read in the book or is it a bit boring? And of course, are there any topics you’d love me to explore?

This Week’s Question

Can the light a mother is exposed to in the evening influence her baby’s development before birth?

For some, this might seem unlikely. For me, it’s a hell yes, but then again, I’m completely biased. So you might be asking: how could the light entering a mother’s eyes possibly affect the baby growing inside her?

And that’s exactly the question researchers set out to investigate.

The Study

In 2022, researchers led by Balserak equipped pregnant women with wearable light sensors that measured their exposure to blue light during the evening. Rather than relying on questionnaires or asking women to estimate their screen time, the researchers objectively measured the amount of blue light each participant experienced after sunset.

They then measured fasting glucose levels during pregnancy and recorded infant birthweight after delivery and their findings were striking.

Women who experienced greater evening blue-light exposure had higher fasting glucose levels and gave birth to babies with higher birthweights.

Now, this was an observational study, meaning it cannot prove that blue light caused these changes. But it raises an intriguing possibility: could our light environment be influencing maternal biology in ways that begin shaping the developing baby long before birth?

If that’s the case, the implications could be significant. Gestational diabetes is becoming increasingly common, with rates rising substantially in the United States in recent years. As maternal blood sugar regulation becomes an increasingly important area of research, scientists are beginning to ask whether our modern light environment could be one of many factors contributing to this trend.

So what could explain this connection?

Could melatonin be the messenger?

Following this question through the scientific literature leads to one hormone that repeatedly appears: melatonin.

Most of us think of melatonin simply as the “sleep hormone”, but it is much more than that. Melatonin is the body’s biological messenger of darkness, rising in the evening as natural light fades to signal that night has arrived. It helps coordinate the circadian rhythms that keep our biology running on time, while also supporting metabolism, immune function and cellular health.

During pregnancy, melatonin takes on another remarkable role. Because it crosses the placenta, a mother’s melatonin rhythm provides one of the earliest timing signals for her developing baby, carrying information about day and night long before the baby’s own circadian clock is fully established.

This makes the timing of light exposure especially interesting. When we expose ourselves to bright, blue-enriched light after sunset, melatonin production is suppressed. Why does that matter? Because our hormones don’t just rise and fall, they follow a daily rhythm. As darkness falls, melatonin rises while cortisol, our daytime hormone, naturally declines.

But what happens if bright light keeps telling the brain it’s still daytime?

One possibility is that the body delays switching into its normal nighttime biology. Instead of winding down, it may continue behaving as though it’s daytime, keeping glucose more readily available, when it would normally be preparing for overnight rest and repair.

Experimental studies have shown that evening blue-enriched light can alter melatonin, cortisol, glucose and insulin responses, while broader circadian disruption is known to impair glucose regulation and insulin sensitivity. This doesn’t prove that cortisol explains the higher fasting glucose levels seen in the pregnant women studied, but it offers one biologically plausible explanation.

In other words, the body may not simply be responding to the amount of light it receives, but to the message that light is sending about what time of day it is.

But the melatonin story doesn’t end there…

During pregnancy, melatonin doesn’t just provide timing signals to the developing baby. As I continued digging through the literature, I discovered it may also play another remarkable role: helping prepare the mother’s body for labour.

One of the most fascinating papers I’ve read, comes from reproductive endocrinologist James Olcese and colleagues. Their work explores the unsurprising possibility, that labour is not randomly timed, but may be influenced by the body’s ancient biological clock. Olcese and colleagues suggests that melatonin may play an active role in preparing the uterus for birth by working together with oxytocin, the hormone responsible for stimulating uterine contractions. The uterus contains melatonin receptors, and laboratory studies using human uterine muscle cells have shown that melatonin can enhance the contractile effects of oxytocin. In other words, as darkness falls and melatonin rises, the uterus becomes more responsive to the very hormone that drives labour forward.

These two hormones appear to work in partnership: oxytocin provides the signal for contraction, while melatonin may help create the biological environment in which that signal becomes more effective.

So you may be wondering - as I have been for many moons now, what happens to women in labour when they’re exposed to bright hospital lights?

Okay, so we do not yet have strong clinical trials proving that bright, blue-enriched hospital lighting stalls labour. But we do know two important things: blue light suppresses melatonin, and melatonin appears to enhance oxytocin’s effects during labour.

And I’m sure many of you know a woman, or perhaps this was your own experience, who arrived at hospital in active labour, only for contractions to suddenly slow down or even stop. Of course, many factors can influence labour and this is where the brilliant work of Dr Sarah Buckley becomes particularly interesting. In Ecstatic Birth: Nature’s Hormonal Blueprint for Labor, she explores how stress, fear, bright light, noise and unnecessary disruption can influence the hormonal processes that allow birth to unfold.

In her comprehensive review of the hormonal physiology of childbirth, she describes birth as an intricate hormonal dance, one in which melatonin, oxytocin, endorphins, adrenaline, and other biological systems work together to support labour.

Seen through this lens, the relationship between light, melatonin and oxytocin becomes even more fascinating. The environment surrounding birth is not simply a backdrop; it is part of the biological conversation between the mother, her hormones and her baby.

Which raises a question I find impossible not to ask: have we underestimated the role of light during labour?

Of course, maternity wards need excellent lighting when clinicians need to assess mother or baby or perform procedures, but when a woman is naturally progressing through labour, it’s worth asking: “could we kindly turn down - or better still, switch off the bright overhead lights when they’re not clinically needed?”

Why this matters for The Light Fix

It matters, because the point of The Light Fix is to show that light is one of the most powerful pieces of biological information we receive every single day. And this research is a perfect example of that. Long before a baby has ever seen its first sunrise, light is already sending biological signals through the mother and helping shape the earliest chapters of life. Surely that’s fascinating stuff?

And that’s why understanding your ‘light diet’ matters.

Just as we think about the food we eat, we should also be thinking about the light we consume each day. Are we getting enough morning light? Too little daylight? Too much artificial light after dark? That’s the journey that hopefully The Light Fix takes you on.

From pregnancy and birth...to childhood and adolescence...through adulthood...and into healthy ageing.

The story of light doesn’t begin when we open our eyes, it begins long before we’re born.

Next in The Light Fix Files

In my next post, we’ll move from the womb to the teenage years.

Why do teenagers naturally become night owls? Is it really their phones, or does puberty fundamentally reset the body’s internal clock?

And as always, if there are any topics you’d particularly like me to cover in the chapter, just let me know. I’d love to hear your suggestions.

References:

1. Evening blue-light exposure, maternal glucose, and infant birthweight
   Izci Balserak B, Hermann R, Hernandez TL, Buhimschi C, Park C. (2022).
   Annals of the New York Academy of Sciences, 1515(1), 276–284.
   https://doi.org/10.1111/nyas.14852
   PMID: 35764595

2. Melatonin and the Circadian Timing of Human Parturition
   Olcese J, Lozier S, Paradise C. (2013).
   Reproductive Sciences, 20(2), 168–174.
   https://doi.org/10.1177/1933719112442244
   PMID: 22556015

3. Melatonin synergizes with oxytocin to enhance contractility of human myometrial smooth muscle cells
   Sharkey JT, Puttaramu R, Word RA, Olcese J. (2009).
   Journal of Clinical Endocrinology & Metabolism, 94(2), 421–427.
   https://doi.org/10.1210/jc.2008-1723
   PMID: 19001515

4. Melatonin Sensitizes Human Myometrial Cells to Oxytocin in a Protein Kinase Cα/Extracellular Signal-Regulated Kinase-Dependent Manner
   Sharkey JT, Cable C, Olcese J. (2010).
   Journal of Clinical Endocrinology & Metabolism, 95(6), 2902–2908.
   https://doi.org/10.1210/jc.2009-2137

5. Gentle Birth, Gentle Mothering: The Wisdom and Science of Gentle Choices in Pregnancy, Birth, and Parenting
   Buckley SJ. (2009).
   One Moon Press.

6. Ecstatic Birth: Nature’s Hormonal Blueprint for Labour
   Buckley SJ.
   https://sarahbuckley.com/ecstatic-birth-natures-hormonal-blueprint-for-labour/