Is It Safe To Run A Marathon While Pregnant?

Read Time: 5 Mins

Running a marathon while pregnant is a bit of a controversial topic. Women may get both concerned stares and cheers for their choice to participate. It is understandable why people might be both worried and impressed. Racing a marathon can be a grueling athletic challenge for even the fittest of athletes. Runners often deal with dehydration, muscle cramps, and energy depletion, not to mention the extensive training and time required to prepare for the race.

So the question stands- can a marathon be safely run while pregnant? If so, what modifications need to be made to train and run safely? To answer this question, we decided to dig into the research, discuss the risks and survey women who have completed a marathon while pregnant to learn more.

Presented below are commonly stated concerns and risks relating to marathons and pregnancy, as well as what research tells us about their severity. 

  • Abnormal fetal heart rate, or reduced blood flow to the uterus.
  • Baby’s heart rate is unlikely to be abnormal as long as the mother keeps her heart rate under 90% of max heart rate. If a well conditioned runner runs at a moderate pace, it is unlikely she will go over this rate (Zavorsky and Longo, 2012).
  • With increased exercise intensity and duration, fetal blood supply does decrease. However, the body uses several defense mechanisms to maintain fetal oxygen supply during intense exercise. So while fetal blood supply may decrease during intense exercise, fetal oxygen delivery via the umbilical cord is minimally affected. (Zavorsky and Longo, 2012). 
  • Mother could overheat, which could cause neural tube defects for baby.
  • The risk of the mother overheating is only a concern in the 1st trimester, and the risk is fairly low. Though moderate exercise will not normally increase core temperature to a dangerous level, attention should be paid to weather conditions (Zavorsky and Longo, 2012)
  • Dehydration could cause complications
  • Pregnant women have higher fluid needs than a typical person, and there are risks to both mother and baby associated with dehydration (decreased levels of amniotic fluid, preterm labor etc.). Increased hydration during training and racing is essential! For more information on dehydration and pregnancy, see articles here and here.
  • Changes in running form could lead to injury over long distances
  • It’s true that pregnant women run differently! Changes in running gait include a wider stance, longer contact time, and an anterior pelvic tilt (among other things) (Forczek et al. 2018). Consequently, strength work is imperative for all pregnant women! Strength work should include all major muscle groups- but have a particular emphasis on strengthening the core, hips and glutes.
  • Pelvic floor damage from repeated impact
  • High impact exercise is generally safe during pregnancy as long as it is accompanied by proper pelvic floor strengthening (Szumilewicz et al. 2018). Some studies have found running to actually improve strength and reflexes in pelvic floor muscles (Leitner et al. 2016, Szumilewicz et al. 2018). 
  • It is important to note that while running does not directly cause urinary incontinence or prolapse, it does cause repeated, rapid increases in intra abdominal pressure which could exacerbate existing conditions. Wearing a support belt like the ReCORE FITsplint while running may help take pressure off the bladder.
  • Risk of preterm birth or low birth weight
  • Running while pregnant will not increase risk of preterm birth and low birth weight, regardless of weekly mileage or stage of pregnancy (Kuhrt et al, 2018). 

Other considerations:

It is important to consider previous training. A runner who is accustomed to long distance training and marathons would not find a pregnant marathon as physically taxing as someone completing their first marathon while pregnant.

Additionally, it is essential to obtain a doctor’s clearance, as certain conditions during pregnancy may make exercise more risky (preeclampsia, placenta previa after 26 weeks, heart or lung disease etc. Find full list here.) It is also important to know warning signs that may indicate that you are training too hard or causing distress to baby (vaginal bleeding, dizziness, painful contractions etc. Find full list here).

Note: if you are interested in reading more about these topics, much of our information was pulled from a fantastic research review article written by Zavorsky and Longo (2012), as well as a very well researched web article written by Dr. Tracy Høeg (2017). See the full articles here and here.

If you are considering running a marathon while pregnant, we would present the following safety checklist:

  • -Obtain doctor’s clearance.
  • -Be accustomed to marathon training before pregnancy, or have run a marathon recently.
  • -No high risk pregnancy.
  • -Run marathon at an easy to moderate pace. Be sure to keep heart rate below 90% of max heart rate.
  • -Stay properly fueled and hydrated with electrolytes (according to increased needs during pregnancy).
  • -Consider wearing a maternity support belt for pelvic, bladder and back support. 
  • -Keep hips, glutes, core and pelvic floor strong.
  • -Stop running if you experience pain or any contraindications to exercise (see list above). 

While running a marathon during pregnancy can be done safely with above recommendations, please note:

- Running long distances in pregnancy does not equate to healthier or more fit pregnancy!

- Running long distance does not necessarily make labor easier!

- ACOG Guidelines recommends at least 150 min/week of aerobic exercise at a moderate exertion level during pregnancy.

- Please consult your physician before beginning any exercise program.


Forczek, W., Ivanenko, Y. P., Bielatowicz, J., & Wacławik, K. (2018). Gait assessment of the expectant mothers – Systematic review. Gait & Posture, 62, 7–19.

Høeg, T. B. (2017, December 29). Baby on board: Long-distance running during pregnancy. iRunFar. 

Kuhrt, K., Harmon, M., Hezelgrave, N. L., Seed, P. T., & Shennan, A. H. (2018). Is recreational running associated with earlier delivery and lower birth weight in women who continue to run during pregnancy? An international retrospective cohort study of running habits of 1293 female runners during pregnancy. BMJ Open Sport & Exercise Medicine, 4(1), e000296.

Leitner, M., Moser, H., Eichelberger, P., Kuhn, A., & Radlinger, L. (2016). Evaluation of pelvic floor muscle activity during running in continent and incontinent women: An exploratory study. Neurourology and Urodynamics, 36(6), 1570–1576. 

Szumilewicz, A., Dornowski, M., Piernicka, M., Worska, A., Kuchta, A., Kortas, J., Błudnicka, M., Radzimiński, Ł., & Jastrzębski, Z. (2019). High-low impact exercise program including pelvic floor muscle exercises improves pelvic floor muscle function in healthy pregnant women – a randomized control trial. Frontiers in Physiology, 9. 

Zavorsky, G. S., & Longo, L. D. (2012). Viewpoint: Are there valid concerns for completing a marathon at 39 weeks of pregnancy? Journal of Applied Physiology, 113(7), 1162–1165.

Aubree McLeod
Aubree McLeod
ReCORE Trainer/Research Associate

Aubree McLeod is an ACSM-EP exercise physiologist, researcher in running biomechanics. She has also completed the ICE Preg & PostPartum Course for athletes. She has an M.S. in Exercise Science and has worked in a variety of spaces within the exercise science field including physical therapy, education, research, and run coaching for... Read More