Babies born in November are up to 10% stronger than babies born in June & the reason is quite interesting...
This sunlight data shocked me…
I hope you are having a fantastic Sunday.....I came across this research last week & thought it would be fun to discuss in an article today.
The research on birth month and fetal development tells a very interesting story, and it's that babies born in late fall (September–November) consistently demonstrate:
higher bone mineral density
stronger grip strength
better muscle function
better cardiorespiratory fitness
Keep reading for the article (and what I did during pregnancy)
🚨 My holiday sale starts next week - but you can grab this limited bundle early if you are ready to get started today! (a testimonial from the bundle below ⬇️⬇️)
Now let's talk about that very interesting data....
Why fall babies come out stronger in the research
The key is the mother’s third trimester - the period when fetal bones, neuromuscular strength, and early metabolic programming rapidly develop.
If a mother’s third trimester happens in summer, she is more likely to naturally receive:
more UVB
higher natural vitamin D
stronger fetal bone mineralization
improved early muscle development
Those babies are born in late fall.
But if the third trimester happens in winter (especially above ~37° latitude), she receives:
little to no UVB
lower vitamin D
potentially weaker fetal bone mineralization
Those babies are born in late spring or early summer.
This is not a hypothesis - it’s documented across multiple human cohorts.
In ~8,000 English children, those born in November had significantly higher grip strength, cardiorespiratory fitness, and lower-body power than those born in spring/early summer.
Season of birth correlates with birth weight and developmental trajectories (supportive context).
Why this matters for adults (and what I did when I was pregnant in the winter)
Your biology is shaped by the light environment you were built in, and circadian biology starts before birth.
So if sunlight during pregnancy can influence lifelong bone density and muscle function…
Imagine what the light you get (or don’t get) today is doing to:
your appetite
your cortisol rhythm
your sleep
your metabolism
your thyroid
your energy
your mitochondrial signaling
This is why I say over and over:
Vitamin D isn’t a supplement issue - it’s a sunlight environment issue.
Our biology was never designed for a low-light, indoor, blue-heavy world, and Your birth month doesn’t necessarily determine your destiny - but this data reveals something deeper:
Sunlight is developmental, circadian, hormonal & metabolic.
If prenatal sunlight can change these sorts of outcomes for babies, it can absolutely change metabolism & health outcomes in adults!
Now I know you are thinking - what about the women who are pregnant right now & know the value of UVB for their baby? (I can only give my own personal experience here & it's not medical advice)
Most people only think about vitamin D levels when they’re already low.
During pregnancy, I approached it differently.
I wanted my levels to be optimal before winter, and I wanted to maintain them without relying on high-dose vitamin D supplementation, especially after reading the work of Jim Stephenson Jr. on vitamin D metabolism, D/A ratios, and long-term safety considerations.
I've also been testing this lamp - but haven't done actual bloodwork yet (the way I did with the above combo) - to know how well it performs! Stay tuned & I will let you know what I think!
Want my exact UVB + Red light protocol that I did during pregnancy? I created a brand new Substack where I will post protocols regularly.
