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 22 • 4:00 PM

The Invention of the Illegal Immigrant

It’s only fairly recently that we started to use the term that’s so popular right now.



August 22 • 2:00 PM

What Can U.S. Health Care Learn From the Ebola Outbreak?

A conversation with Jeanine Thomas, patient advocate, active member of ProPublica’s Patient Harm Facebook Community, and founder and president of the MRSA Survivors Network.


August 22 • 1:22 PM

Two Executions and the Unity of Mourning

The recent deaths of Michael Brown and James Foley, while worlds apart, are both emblematic of the necessity for all of us to fight to uphold the sanctity of human dignity and its enduring story.


August 22 • 10:00 AM

Turbo Paul: Art Thief Turned Art Crime Ombudsman

There’s art theft, there’s law enforcement, and, somewhere in between, there’s Turbo Paul.


August 22 • 8:00 AM

When Climate Change Denial Refutes Itself

The world is warming—and record-cold winters are just another symptom.


August 22 • 6:17 AM

The Impossibility of the Night Shift

Many night workers get “shift-work sleep disorder.” And no one knows how to treat it.


August 22 • 6:00 AM

Long Live Short Novels

Christopher Beha’s Arts & Entertainments comes in at less than 300 pages long, which—along with a plot centered on a sex-tape scandal—makes it a uniquely efficient pleasure.


August 22 • 4:00 AM

Why ‘Nature Versus Nurture’ Often Doesn’t Matter

Sometimes it just doesn’t make any sense to try to separate the social and the biological.


August 21 • 4:00 PM

Julie Chen Explains Why She Underwent Westernizing Surgery

The CBS news anchor and television personality’s story proves that cosmetic surgeries aren’t always vanity projects, even if they’re usually portrayed that way.


August 21 • 2:37 PM

How the Brains of Risk-Taking Teens Work

There’s heightened functional connectivity between the brain’s emotion regulator and reason center, according to a recent neuroscience paper.


August 21 • 2:00 PM

Cracking Down on the Use of Restraints in Schools

Federal investigators found that children at two Virginia schools were being regularly pinned down or isolated and that their education was suffering as a result.


August 21 • 12:00 PM

What Makes You So Smart, School Principal?

Noah Davis talks to Evan Glazer about why kids aren’t getting smarter and what his school’s doing in order to change that.



August 21 • 10:00 AM

Why My Neighbors Still Use Dial-Up Internet

It’s not because they want to. It’s because they have no other choice.


August 21 • 8:15 AM

When Mothers Sing, Premature Babies Thrive

Moms willing to serenade pre-term infants help their babies—and themselves.


August 21 • 8:00 AM

To Fight the Obesity Epidemic Americans Will Have to First Recognize That They’re Obese

There is a void in the medical community’s understanding of how families see themselves and understand their weight.


August 21 • 6:33 AM

One Toxic Boss Can Poison the Whole Workplace

Office leaders who bully even just one member of their team harm everyone.


August 21 • 6:00 AM

The Fox News Effect

Whatever you think of its approach, Fox News has created a more conservative Congress and a more polarized electorate, according to a series of recent studies.


August 21 • 4:00 AM

Do Children Help Care for the Family Pet?

Or does mom do it all?


August 20 • 4:00 PM

Why Can’t Conservatives See the Benefits of Affordable Child Care?

Private programs might do a better job of watching our kids than state-run programs, but they’re not accessible to everyone.


August 20 • 2:00 PM

Oil and Gas Companies Are Illegally Using Diesel Fuel in Hundreds of Fracking Operations

An analysis by an environmental group finds hundreds of cases in which drillers used diesel fuel without obtaining permits and sometimes altered records disclosing they had done so.


August 20 • 12:00 PM

The Mystery of Britain’s Alien Big Cats

In a nation where the biggest carnivorous predator is a badger, why are there so many reported sightings of large cats?


August 20 • 10:00 AM

Death Row in Arizona: Where Human Experimentation Is the Rule, Not the Exception

Recent reports show that chemical roulette is the state’s M.O.


August 20 • 9:51 AM

Diversity Is in the Eye of the Beholder

Perception of group diversity depends on the race of the observer and the extent to which they worry about discrimination.


Follow us


The Impossibility of the Night Shift

Many night workers get “shift-work sleep disorder.” And no one knows how to treat it.

How the Brains of Risk-Taking Teens Work

There's heightened functional connectivity between the brain's emotion regulator and reason center, according to a recent neuroscience paper.

When Mothers Sing, Premature Babies Thrive

Moms willing to serenade pre-term infants help their babies—and themselves.

One Toxic Boss Can Poison the Whole Workplace

Office leaders who bully even just one member of their team harm everyone.

Diversity Is in the Eye of the Beholder

Perception of group diversity depends on the race of the observer and the extent to which they worry about discrimination.

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
Subscribe Now

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