Menus Subscribe Search

Study: Soaking Up Rays May Produce Bigger Babies

• June 02, 2009 • 10:30 PM

Ultraviolet sunlight exposure in the third trimester of pregnancy may be related to increased height and bone health of children.

After years of hearing it can cause first-degree burns, skin cancer and accelerated aging, some good news about ultraviolet sunlight has emerged: Increased height and bone health of children is related to the amount of sunlight mothers receive while pregnant.

According to research published in the March edition of the Journal of Clinical Endocrinology and Metabolism, children born in the late summer and early fall are taller and have higher bone density and mineral content than their counterparts because their mothers are exposed to greater levels of UVB rays during the third trimester.

To determine the relationship between ambient maternal sunlight exposure and child bone health, Adrian Sayers and Jonathan Tobias, two University of Bristol rheumatology researchers, first consulted the medical records of nearly 7,000 children participating in the Avon Longitudinal Study of Parents and Children. ALSPAC is an ongoing long-term health research project that monitors the health and development of 14,000 children born to English mothers between April 1991 and December 1992. Then, Sayers and Tobias used historical meteorological records for the region around Bristol and Bath to calculate total environmental UVB levels each mother experienced during the 98 days prior to giving birth.

Statistical analysis of their database revealed children born after third trimesters with high total UVB levels (i.e. births between June and October) had longer birth lengths and greater height and weight than those born during the winter and early spring. For every four weeks of “summer” sunlight a mother had above the average, the height and weight of the child at 10 years of age increased by 0.18 centimeters and 0.1 pounds respectively. (The study did not track how much any individual spent in the sun for those summer months.)

The strongest association, however, was between UVB exposure and greater bone area, density and mineral content when the child was 10 years old. Four weeks of summer sun exposure was associated with increases of 8.1 cm2 in bone area, 0.003 g/cm2 in bone density and 9.6 gram in bone mineral content. While small, these results indicate elevated sunlight exposure reduces fracture risk of the child by approximately 5 percent (normally the association is reversed and fracture risk increases in taller individuals).

Sayers and Tobias believe the positive trend height, weight and bone characteristics are due to greater levels of vitamin D in the mother during the third trimesters when critical, early skeletal development occurs in the womb (UVB rays play a key role in generating vitamin D in the body). Their findings are consistent with other studies focusing on in utero vitamin D levels and offspring health, but this study was the first to include enough participants to create statistically significant results. Past studies have reported increased vitamin D is not only associated with greater bone mineral content but also the lowered risk of Type 1 diabetes and asthma.

While many women may be looking for a good reason to sunbathe, Sayers and Tobias emphasize that the results of this study are not suggesting mothers should risk sun damage for possible improved health of their unborn child. Instead, Tobias was quoted in a press release, “Pregnant women might consider talking to their doctor about taking vitamin D supplements, particularly if their babies are due between November and May, when sunlight levels are low.”

Julia Griffin
Julia Griffin is a master's candidate in environmental science and management at the University of California, Santa Barbara. A fellow at the Miller-McCune Center in 2009, before that she worked as a film researcher for John-Michel Cousteau's Ocean Future Society and a producer/writer in CNN's Science and Technology Unit. She has a degree in marine biology from Duke University, and hopes to pursue a career in science and environmental journalism.

More From Julia Griffin

A weekly roundup of the best of Pacific Standard and PSmag.com, delivered straight to your inbox.

Recent Posts

August 29 • 4:00 PM

The Hidden Costs of Tobacco Debt

Even when taxpayers aren’t explicitly on the hook, tobacco bonds can cost states and local governments money. Here’s how.


August 29 • 2:00 PM

Why Don’t Men and Women Wear the Same Gender-Neutral Bathing Suits?

They used to in the 1920s.


August 29 • 11:48 AM

Your Brain Decides Whether to Trust Someone in Milliseconds

We can determine trustworthiness even when we’re only subliminally aware of the other person.


August 29 • 10:00 AM

True Darwinism Is All About Chance

Though the rich sometimes forget, Darwin knew that nature frequently rolls the dice.


August 29 • 8:00 AM

Why Our Molecular Make-Up Can’t Explain Who We Are

Our genes only tell a portion of the story.


August 29 • 6:00 AM

Strange Situations: Attachment Theory and Sexual Assault on College Campuses

When college women leave home, does attachment behavior make them more vulnerable to campus rape?


August 29 • 4:00 AM

Forgive Your Philandering Partner—and Pay the Price

New research finds people who forgive an unfaithful romantic partner are considered weaker and less competent than those who ended the relationship.


August 28 • 4:00 PM

Some Natural-Looking Zoo Exhibits May Be Even Worse Than the Old Concrete Ones

They’re often designed for you, the paying visitor, and not the animals who have to inhabit them.


August 28 • 2:00 PM

What I Learned From Debating Science With Trolls

“Don’t feed the trolls” is sound advice, but occasionally ignoring it can lead to rewards.


August 28 • 12:00 PM

The Ice Bucket Challenge’s Meme Money

The ALS Association has raised nearly $100 million over the past month, 50 times what it raised in the same period last year. How will that money be spent, and how can non-profit executives make a windfall last?


August 28 • 11:56 AM

Outlawing Water Conflict: California Legislators Confront Risky Groundwater Loophole

California, where ambitious agriculture sucks up 80 percent of the state’s developed water, is no stranger to water wrangles. Now one of the worst droughts in state history is pushing legislators to reckon with its unwieldy water laws, especially one major oversight: California has been the only Western state without groundwater regulation—but now that looks set to change.


August 28 • 11:38 AM

Young, Undocumented, and Invisible

While young migrant workers struggle under poor working conditions, U.S. policy has done little to help.


August 28 • 10:00 AM

The Five Words You Never Want to Hear From Your Doctor

“Sometimes people just get pains.”


August 28 • 8:00 AM

Why I’m Not Sharing My Coke

Andy Warhol, algorithms, and a bunch of popular names printed on soda cans.


August 28 • 6:00 AM

Can Outdoor Art Revitalize Outdoor Advertising?

That art you’ve been seeing at bus stations and billboards—it’s serving a purpose beyond just promoting local museums.


August 28 • 4:00 AM

Linguistic Analysis Reveals Research Fraud

An examination of papers by the discredited Diederik Stapel finds linguistic differences between his legitimate and fraudulent studies.


August 28 • 2:00 AM

Poverty and Geography: The Myth of Racial Segregation

Migration, regardless of race, ethnicity, gender, or sexuality (not to mention class), can be a poverty-buster.


August 27 • 4:00 PM

The ‘Non-Lethal’ Flash-Bang Grenades Used in Ferguson Can Actually Be Quite Lethal

A journalist says he was singed by a flash-bang fired by St. Louis County police trying to disperse a crowd, raising questions about how to use these military-style devices safely and appropriately.


August 27 • 2:00 PM

Do Better Looking People Have Better Personalities Too?

An experiment on users of the dating site OKCupid found that members judge both looks and personality by looks alone.


August 27 • 12:00 PM

Love Can Make You Stronger

A new study links oxytocin, the hormone most commonly associated with social bonding, and the one that your body produces during an orgasm, with muscle regeneration.


August 27 • 11:05 AM

Education, Interrupted

When it comes to educational access, young Syrian refugees are becoming a “lost generation.”


August 27 • 9:47 AM

No, Smartphone-Loss Anxiety Disorder Isn’t Real

But people are anxious about losing their phones, even if they don’t do much to protect them.


August 27 • 8:00 AM

A Skeptic Meets a Psychic: When You Can See Into the Future, How Do You Handle Uncertainty?

For all the crystal balls and beaded doorways, some psychics provide a useful, non-paranormal service. The best ones—they give good advice.


August 27 • 6:00 AM

Speaking Eyebrow: Your Face Is Saying More Than You Think

Our involuntary gestures take on different “accents” depending on our cultural background.


August 27 • 4:00 AM

The Politics of Anti-NIMBYism and Addressing Housing Affordability

Respected expert economists like Paul Krugman and Edward Glaeser are confusing readers with their poor grasp of demography.


Follow us


Subscribe Now

Your Brain Decides Whether to Trust Someone in Milliseconds

We can determine trustworthiness even when we’re only subliminally aware of the other person.

Young, Undocumented, and Invisible

While young migrant workers struggle under poor working conditions, U.S. policy has done little to help.

Education, Interrupted

When it comes to educational access, young Syrian refugees are becoming a “lost generation.”

No, Smartphone-Loss Anxiety Disorder Isn’t Real

But people are anxious about losing their phones, even if they don’t do much to protect them.

Being a Couch Potato: Not So Bad After All?

For those who feel guilty about watching TV, a new study provides redemption.

The Big One

One in two full-time American fast-food workers' families are enrolled in public assistance programs, at a cost of $7 billion per year. July/August 2014 fast-food-big-one

Copyright © 2014 by Pacific Standard and The Miller-McCune Center for Research, Media, and Public Policy. All Rights Reserved.