Largest ever study of running habits shows that running in pregnancy is safe

The international retrospective study of 1,293 women who take part in parkrun found no evidence of negative effects of running on the baby.
  • Running during pregnancy did not affect the number of weeks babies were born, or the birthweight of the baby.
  • The results were shown in the largest ever study of running in pregnancy which has been published in BMJ Open Sport & Exercise Medicine.
  • The international retrospective study looked at 1,293 women who take part in parkrun.
  • More than a third of women said they are unsure about the safety of running so this research should be communicated widely to the running community.

The largest ever international study of pregnant runners has found no evidence of negative effects of running on the baby.

Nearly 1,300 women were recruited from parkrun, which organises weekly five kilometre runs across the world. Women were categorised according to whether they continued to run during pregnancy or not. Information was collected on how many weeks into her pregnancy a woman ran, and how many kilometres she ran each week.

A poll of 1,116 women on the Tommy’s pregnancy website, showed that more than a third were unsure if it was safe for regular runners to continue to run whilst pregnant, so the study is good news for runners.

Women from around the world responded to parkrun’s newsletter, making the study truly global. Details of previous pregnancies were collated, including gestation of delivery, birthweight and pregnancy complications. These were related to expected baby size by taking into account the mothers’ ethnicity, height, weight, and her baby’s gender, allowing an accurate assessment of running impact on pregnancy.

The results found that there were no ill effects related to the intensity or frequency of running during pregnancy and that continuing to run into the third trimester was safe. One woman ran a marathon the day before she delivered at term, while others ran regular half marathons throughout pregnancy. Even women pregnant with triplets enjoyed parkrun regularly.

Women are advised to exercise during pregnancy as it can lead to many health benefits and help women prepare for labour.

“There are over 2.8 million park runners across the globe, many of whom are of reproductive age. With parkrun’s assistance, in the biggest ever study of its kind, we have determined that running in pregnancy is safe. Women can continue accustomed exercise during pregnancy and we would encourage this to ensure a healthy outcome for both her and her baby.”
Professor Andrew Shennan, lead author of the study and Professor of Obstetrics and Tommy’s Clinical Director at Guy’s and St Thomas’ Hospital

Katy Kuhrt, study co-author and Research Fellow, Women’s Health Academic Group, Guy’s and St Thomas’ Hospital, comments, “The beneficial effects of running, including cardiovascular conditioning, reduced heart rate and blood pressure at rest, improved lung function, and a reduction in fat levels, have long been recognised. But the effect of regular, strenuous running on pregnancy health has been debated, and there is theoretical concern about adverse effects on pregnancy outcomes. We investigated whether the duration and intensity of running in pregnancy affects the number of weeks at which a baby is born and/or the birthweight of the baby.”

“We recommend that all women take part in regular exercise during pregnancy as it can help to reduce fatigue, lower back pain, varicose veins, swelling of the ankles, and feelings of stress, anxiety and depression. This new study shows that, in the majority of cases, it is safe for both the mother and the baby if a woman who runs regularly continues to do so during her pregnancy.” Professor Janice Rymer, Vice President for Education at the Royal College of Obstetricians and Gynaecologists (RCOG)

Abi Gooch is a 40-year-old police firearms officer from Milton Keynes. She’s been running for over 20 years, regularly takes part in triathlons and marathons, and needs to pass an annual fitness test for her job.

“I ran through both of my pregnancies and was fit and healthy throughout. I did a marathon when my first daughter was 7 months old and got a PB. With my second daughter I did parkrun on Saturday, a spin class on the Monday and gave birth to my daughter with a 4-hour labour on the Wednesday. Two weeks later I took part in a local 1-mile relay race.

“It doesn’t surprise me that running has been deemed safe during pregnancy. If you’re used to doing it and you still feel comfortable then why stop. It’s great for mental health, keeping the body strong for labour and I also found I got back to fitness quickly afterwards. I also found it helped me keep my identity and not just ‘a pregnant lady’ or ‘Mum’, I was still ‘me’. I have since completed over 50 marathons including some Ultra marathons and the Marathon Des Sables.”

“If you ran or jogged regularly before your pregnancy, you can carry on for as long as you feel comfortable. It’s a great aerobic exercise and can help women have a healthy pregnancy.”
Sophie King, Tommy’s midwife

Tips for pregnant runners 

  • Wear supportive running shoes and a proper bra that has been designed for runners
  • Focus on good technique rather than a fast pace
  • Look where you’re going so you avoid falling or colliding with anything
  • Don’t run yourself to exhaustion
  • If you experience any unusual symptoms, stop exercising and contact your doctor or midwife.
  • 1293 female participants were recruited from parkrun, which organises weekly runs across the world, including 691 in the UK.
  • Women were categorized according to whether they continued to run during pregnancy or not.
  • Information on how many weeks into her pregnancy a woman ran, and how many kilometres she ran each week.

For more information or to request an interview with Professor Andrew Shennan, Dr Katy Kuhrt or the case studies, please contact the Tommy's press office on 0207 398 3436 or email [email protected] 

To request an interview with Professor Janice Rymer, please contact Tara Meakins, Press Officer at the RCOG
E: [email protected] or T: 07715 677 224

About Tommy's

Tommy’s is the largest pregnancy and baby charity in the UK. We fund research into pregnancy problems and provide pregnancy health information to parents-to-be. We believe it is unacceptable that one in four women lose a baby during pregnancy and birth. With four research centres across the UK investigating the causes of miscarriage, stillbirth and premature birth, we lead the way in maternal and fetal research in the UK.

Our pregnancy health information is provided through the midwife-led Tommy’s Pregnancy Health Service, which includes our comprehensive pregnancy information website, our Tommy’s Midwives facebook page and our free Midwives helpline, the PregnancyLine. We believe every pregnancy should have a happy ending and that every baby should have the best chance of being born healthy.

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About the RCOG

The Royal College of Obstetricians and Gynaecologists is a medical charity that champions the provision of high quality women’s healthcare in the UK and beyond. It is dedicated to encouraging the study and advancing the science and practice of obstetrics and gynaecology. It does this through postgraduate medical education and training and the publication of clinical guidelines and reports on aspects of the specialty and service provision.