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Study: Getting Sun During Pregnancy May Reduce Risk of Preterm Birth

pregnant woman sunshine

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Key Takeaways

  • Researchers found that pregnant women who had higher levels of sun exposure during their first trimester were at lower risk for preterm birth.
  • Sun exposure may help boost vitamin D levels, which have been previously linked to pregnancy outcomes.
  • More research is needed to investigate the link, but getting some sunlight won't hurt.

Pregnant women who get more sunlight in their first trimester of pregnancy may have a lower risk of preterm birth and pregnancy loss, according to new research.

The July study, which was published in Frontiers in Reproductive Health, analyzed health records of nearly 400,000 moms and more than 500,000 babies who were born in Scotland after 24 weeks of pregnancy. The researchers cross-checked the data with weather records from the same timeframes to measure sunlight exposure.

The overall risk of preterm birth was 6%, but it dropped for those who were exposed to more sunlight in their first trimester.

The researchers found that women who were exposed to more sunlight in their first trimester had a 10% lower risk of developing problems with their placenta that are linked to preterm birth and baby loss compared to those with less sunlight exposure.

However, the researchers did not find a link between sun exposure and premature birth risk in the second trimester.

“This opens up new mechanisms, and potential therapeutic pathways, for preterm birth prevention,” the researchers wrote.

In fact, the team is reportedly studying if artificial light can boost pregnancy health to help parents who live in areas with less sunlight.

Preterm birth happens when a baby is born before 37 weeks of pregnancy. Preterm babies have a higher risk of serious health complications than their full-term counterparts. Those can include lifelong health problems like cerebral palsy and learning disabilities.

Many women who give birth prematurely have no known risk factors. However, some known risk factors can include:

  • Previous preterm birth
  • Short cervix
  • Early cervical dilation
  • Past procedures on the cervix
  • Injury during a past delivery
  • Carrying more than one fetus
  • Vaginal bleeding during pregnancy
  • Infections during pregnancy
  • Low pre-pregnancy weight
  • Smoking during pregnancy
  • Dietary deficiencies
  • Being younger than 17 or older than 35

Why Might Sunlight Exposure Help?

The study didn’t investigate why sunlight may help, but study co-author Sarah Stock, PhD, a maternal-fetal medicine researcher at The University of Edinburgh, tells Verywell that there are some theories.

“Sunlight causes the release of nitric oxide from the skin that relaxes blood vessels, and we believe this could help a healthy pregnancy to establish in the womb,” she says. “Nitric oxide also may relax the womb itself, helping to prevent early contractions.”

Another theory, Stock says, is that the link between preterm birth and sunlight is more about vitamin D, which your body produces when it’s exposed to sunlight.

“Some studies have shown that preterm birth rates are higher in women with low vitamin D levels, which may be because vitamin D helps prevent infections that can lead to preterm birth,” Stock says.

Vitamin D also “aids the development of the baby's bones, teeth, cardiovascular and nervous systems,” women’s health expert Jennifer Wider, MD, tells Verywell.

What This Means For You

The reasons for preterm birth can be complicated, but getting sun exposure during your first trimester may help lower your risk. Consider trying to take a walk outside regularly during daylight hours or sitting out in the sun for a few minutes. Just don’t forget to apply sunscreen first.

How to Lower the Risk of Preterm Birth

There are a few steps you can take to lower your risk of preterm birth.

“Definitely take a prenatal multivitamin, avoid tobacco and secondhand smoke, exercise, and eat a well-balanced diet,” Wider says.

It's also crucial to make regular appointments with your healthcare provider, she adds.

Another important step to take, Stock says, is to get vaccinated against COVID-19 if you haven’t already since research has found a link between having the virus and preterm birth. Both the Centers for Disease Control and Prevention (CDC) the American College of Obstetricians and Gynecologists (ACOG) now recommend that pregnant people get vaccinated.

As for sunlight exposure, Stock says that more research is needed before doctors can actually recommend this for patients.

Still, she points out, getting some sunlight during your first trimester can’t hurt. “It seems sensible to avoid sunburn, but not to totally avoid sun exposure,” she says.  

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  1. Megaw L, Clemens T, Daras K, Weller R, Dibben C, Stock S. Higher Sun Exposure in the First Trimester Is Associated With Reduced Preterm Birth; A Scottish Population Cohort Study Using Linked Maternity and Meteorological Records. Frontiers in Reproductive Health. 2021;3. doi:10.3389/frph.2021.674245

  2. Preterm Labor and Birth. American College of Obstetricians and Gynecologists. March 2021.

  3. The association of COVID-19 infection in pregnancy with preterm birth: A retrospective cohort study in CaliforniaThe Lancet Regional Health - Americas. July 30, 2021. DOI: 10.1016/j.lana.2021.100027