Menus Subscribe Search

Follow us


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

October 2 • 6:00 AM

How Do We Know Our Environmental Laws Are Working?

Ask a great white shark.


October 2 • 5:00 AM

Give Us This Day Our Daily Brands

Researchers find identifying with brand-name products reduces religiosity.


October 2 • 4:00 AM

Why Can’t Anyone Break the Women’s Marathon Record?

Paula Radcliffe set the world record in 2003. Since then? No one’s come within three minutes of her mark.


October 1 • 2:00 PM

Most People With Addiction Simply Grow Out of It. Why Is This Widely Denied?

The idea that addiction is typically a chronic, progressive disease that requires treatment is false, the evidence shows. Yet the “aging out” experience of the majority is ignored by treatment providers and journalists.


October 1 • 1:00 PM

Midlife Neuroticism Linked to Alzheimer’s Disease in Old Age

New research from Sweden suggests that the personality dimension is connected to who ultimately suffers from late-in-life dementia.



October 1 • 11:11 AM

The Creative Class Boondoggle in Downtown Las Vegas

On Tony Hsieh and the pseudoscience of “collisions.”


October 1 • 9:14 AM

Mysterious Resting State Networks Might Be What Allow Different Brain Therapies to Work

Deep brain stimulation and similar treatments target the hubs of larger resting-state networks in the brain, researchers find.


October 1 • 6:00 AM

Would You Like a Subscription With Your Coffee?

A new app hopes to unite local coffee shops while helping you find a cheap cup of good coffee.


October 1 • 4:00 AM

How to Plant a Library

Somewhere outside of Oslo, there are 1,000 newly planted spruce trees. One hundred years from now, if everything goes to plan, they’ll be published together as 100 pieces of art.



September 30 • 10:09 AM

Trust Is Waning, and Inequality May Be to Blame

Trust in others and confidence in institutions is declining, while economic inequality creeps up, a new study shows.


September 30 • 8:00 AM

The Psychology of Penmanship

Graphology: It’s all (probably) bunk.



September 30 • 6:00 AM

The Medium Is the Message, 50 Years Later

Five decades on, what can Marshall McLuhan’s Understanding Media tell us about today?


September 30 • 4:00 AM

Grad School’s Mental Health Problem

Navigating the emotional stress of doctoral programs in a down market.


September 29 • 1:21 PM

Conference Call: Free Will Conference


September 29 • 12:00 PM

How Copyright Law Protects Art From Criticism

A case for allowing the copyright on Gone With the Wind to expire.


September 29 • 10:00 AM

Should We Be Told Who Funds Political Attack Ads?

On the value of campaign finance disclosure.


September 29 • 8:00 AM

Searching for a Man Named Penis

A quest to track down a real Penis proves difficult.


September 29 • 6:00 AM

Why Do So Many People Watch HGTV?

The same reason so many people watch NCIS or Law and Order: It’s all a procedural.


September 29 • 4:00 AM

The Link Between Depression and Terrorism

A new study from the United Kingdom finds a connection between depression and radicalization.


September 26 • 4:00 PM

Fast Track to a Spill?

Oil pipeline projects across America are speeding forward without environmental review.


September 26 • 2:00 PM

Why Liberals Love the Disease Theory of Addiction, by a Liberal Who Hates It

The disease model is convenient to liberals because it spares them having to say negative things about poor communities. But this conception of addiction harms the very people we wish to help.


September 26 • 1:21 PM

Race, Trust, and Split-Second Judgments


Follow us


Mysterious Resting State Networks Might Be What Allow Different Brain Therapies to Work

Deep brain stimulation and similar treatments target the hubs of larger resting-state networks in the brain, researchers find.

Trust Is Waning, and Inequality May Be to Blame

Trust in others and confidence in institutions is declining, while economic inequality creeps up, a new study shows.

Dopamine Might Be Behind Impulsive Behavior

A monkey study suggests the brain chemical makes what's new and different more attractive.

School Counselors Do More Than You’d Think

Adding just one counselor to a school has an enormous impact on discipline and test scores, according to a new study.

How a Second Language Trains Your Brain for Math

Second languages strengthen the brain's executive control circuits, with benefits beyond words.

The Big One

One company, Amazon, controls 67 percent of the e-book market in the United States—down from 90 percent five years ago. September/October 2014 new-big-one-5

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