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 31 • 4:00 PM

Should the Victims of the War on Drugs Receive Reparations?

A drug war Truth and Reconciliation Commission along the lines of post-apartheid South Africa is a radical idea proposed by the Green Party. Substance.com asks their candidates for New York State’s gubernatorial election to tell us more.


October 31 • 2:00 PM

India’s Struggle to Get Reliable Power to Hundreds of Millions of People

India’s new Prime Minister Narendra Modi is known as a “big thinker” when it comes to energy. But in his country’s case, could thinking big be a huge mistake?


October 31 • 12:00 PM

In the Picture: SNAP Food Benefits, Birthday Cake, and Walmart

In every issue, we fix our gaze on an everyday photograph and chase down facts about details in the frame.


October 31 • 10:15 AM

Levels of Depression Could Be Evaluated Through Measurements of Acoustic Speech

Engineers find tell-tale signs in speech patterns of the depressed.


October 31 • 8:00 AM

Who Wants a Cute Congressman?

You probably do—even if you won’t admit it. In politics, looks aren’t everything, but they’re definitely something.


October 31 • 7:00 AM

Why Scientists Make Promises They Can’t Keep

A research proposal that is totally upfront about the uncertainty of the scientific process and its potential benefits might never pass governmental muster.


October 31 • 6:12 AM

The Psychology of a Horror Movie Fan

Scientists have tried to figure out the appeal of axe murderers and creepy dolls, but it mostly remains a spooky mystery.


October 31 • 4:00 AM

The Power of Third Person Plural on Support for Public Policies

Researchers find citizens react differently to policy proposals when they’re framed as impacting “people,” as opposed to “you.”


October 30 • 4:00 PM

I Should Have Told My High School Students About My Struggle With Drinking

As a teacher, my students confided in me about many harrowing aspects of their lives. I never crossed the line and shared my biggest problem with them—but now I wish I had.


October 30 • 2:00 PM

How Dark Money Got a Mining Company Everything It Wanted

An accidentally released court filing reveals how one company secretly gave money to a non-profit that helped get favorable mining legislation passed.


October 30 • 12:00 PM

The Halloween Industrial Complex

The scariest thing about Halloween might be just how seriously we take it. For this week’s holiday, Americans of all ages will spend more than $5 billion on disposable costumes and bite-size candy.


October 30 • 10:00 AM

Sky’s the Limit: The Case for Selling Air Rights

Lower taxes and debt, increased revenue for the city, and a much better use of space in already dense environments: Selling air rights and encouraging upward growth seem like no-brainers, but NIMBY resistance and philosophical barriers remain.


October 30 • 9:00 AM

Cycles of Fear and Bias in the Criminal Justice System

Exploring the psychological roots of racial disparity in U.S. prisons.


October 30 • 8:00 AM

How Do You Make a Living, Email Newsletter Writer?

Noah Davis talks to Wait But Why writer Tim Urban about the newsletter concept, the research process, and escaping “money-flushing toilet” status.



October 30 • 6:00 AM

Dreamers of the Carbon-Free Dream

Can California go full-renewable?


October 30 • 5:08 AM

We’re Not So Great at Rejecting Each Other

And it’s probably something we should work on.


October 30 • 4:00 AM

He’s Definitely a Liberal—Just Check Out His Brain Scan

New research finds political ideology can be easily determined by examining how one’s brain reacts to disgusting images.


October 29 • 4:00 PM

Should We Prosecute Climate Change Protesters Who Break the Law?

A conversation with Bristol County, Massachusetts, District Attorney Sam Sutter, who dropped steep charges against two climate change protesters.


October 29 • 2:23 PM

Innovation Geography: The Beginning of the End for Silicon Valley

Will a lack of affordable housing hinder the growth of creative start-ups?


October 29 • 2:00 PM

Trapped in the Tobacco Debt Trap

A refinance of Niagara County, New York’s tobacco bonds was good news—but for investors, not taxpayers.


October 29 • 12:00 PM

Purity and Self-Mutilation in Thailand

During the nine-day Phuket Vegetarian Festival, a group of chosen ones known as the mah song torture themselves in order to redirect bad luck and misfortune away from their communities and ensure a year of prosperity.


October 29 • 10:00 AM

Can Proposition 47 Solve California’s Problem With Mass Incarceration?

Reducing penalties for low-level felonies could be the next step in rolling back draconian sentencing laws and addressing the criminal justice system’s long legacy of racism.


October 29 • 9:00 AM

Chronic Fatigue Syndrome and the Brain

Neuroscientists find less—but potentially stronger—white matter in the brains of patients with CFS.


October 29 • 8:00 AM

America’s Bathrooms Are a Total Failure

No matter which American bathroom is crowned in this year’s America’s Best Restroom contest, it will still have a host of terrible flaws.


Follow us


Levels of Depression Could Be Evaluated Through Measurements of Acoustic Speech

Engineers find tell-tale signs in speech patterns of the depressed.

We’re Not So Great at Rejecting Each Other

And it's probably something we should work on.

Chronic Fatigue Syndrome and the Brain

Neuroscientists find less—but potentially stronger—white matter in the brains of patients with CFS.

Incumbents, Pray for Rain

Come next Tuesday, rain could push voters toward safer, more predictable candidates.

Could Economics Benefit From Computer Science Thinking?

Computational complexity could offer new insight into old ideas in biology and, yes, even the dismal science.

The Big One

One town, Champlain, New York, was the source of nearly half the scams targeting small businesses in the United States last year. November/December 2014

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