Can Exercise Cause Miscarriage?

Exercising during pregnancy. Getty Images Credit: KidStock

Miscarriages are usually no one’s fault. Most doctors in the U.S. will likely tell you that exercise does not cause miscarriages. In fact, doctors often encourage pregnant women to exercise.

However, a Danish study of 92,671 women that was published in the journal BJOG: An International Journal of Obstetrics and Gynaecology in October 2007 found that strenuous exercise before the 18th week of pregnancy may increase the risk of miscarriages. So what did they find?

Impact of Intense Exercise

The researchers in this study found a correlation between the number of hours per week that a woman exercised and the likelihood of miscarriage, as well as an association between high-impact exercise and miscarriage. Women who worked out intensely were 3.5 times as likely to miscarry, compared with women who didn't work out at all.

Jogging, ball games, and racket sports seemed to carry the greatest risks as well as being physically active for more than seven hours per week.

Previous studies of exercise and miscarriage found no link between the two, and these researchers did urge caution in interpreting the results. Not only can the retrospective data collection procedure used in this study be prone to bias, but more importantly, correlation does not necessarily mean causation. Meaning that an observed relationship does not mean that one variable caused the other.

This study found that exercise was associated with miscarriages, but there may be several explanations for the relationship. For instance, one possible explanation is that women who were destined to miscarry may have suffered less morning sickness and, therefore, were more inclined to exercise strenuously. At present, we simply do not know.

Causes of Miscarriage

If you have had a pregnancy loss, it is natural to speculate about whether something that you did might have caused it, but remember that the majority of early pregnancy losses result from chromosomal abnormalities, and exercise does not change a baby’s chromosomal makeup.

It is unlikely that exercise is a factor in the majority of miscarriages, but it may be a concern for some women. If you are planning a pregnancy, talk to your doctor about whether you should make modifications to your exercise regimen.

General Recommendations 

The American Congress of Obstetricians and Gynecologists (ACOG) has a lot of great information about exercise during pregnancy

The ACOG's overall stance is that exercise in pregnancy "has minimal risks and has been shown to benefit most women, although some modification to exercise routines may be necessary" because of the way your body changes during pregnancy.

When you're pregnant, the ligaments that support your joints relax, which increases your risk for injury. Plus, your center of gravity shifts as your body grows, which can put more pressure on your pelvis and lower back and cause you to lose your balance more easily.


Here is more of the American Congress of Obstetricians and Gynecologists' advice in a nutshell:

  • Keep in mind the benefits of exercise. Regular movement during pregnancy can maintain your endurance and strength, keep your weight under control (no more than 25 to 35 additional pounds is generally recommended if you become pregnant at a healthy weight), reduce your risk of gestational diabetes, backaches, constipation, and swelling, boost your energy, help you sleep better and stand up straighter, and improve your mental state. 
  • Consider your fitness level. If you jogged regularly before you were pregnant, then your doctor is likely to let you jog during your pregnancy. (But you may find that moving around that vigorously while pregnant is not comfortable.) If you weren't a runner before you were pregnant, jogging probably isn't a good idea, and you should start an exercise routine gradually.
  • Think about your pregnancy. Are you having complications with your pregnancy? If your pregnancy is riskier than usual, your doctor might limit your physical activity. 
  • Focus on low-impact activities. Brisk walking and swimming are two types of exercises that are easy on the body but are still good cardiovascular workouts. Many yoga poses are safe during pregnancy (some gyms even offer prenatal yoga classes) but don't do any exercises on your back in the second and third trimesters.
  • Ask your doctor about moderate activities. Certain exercises are debatable. Some types of lightweight lifting might be okay, but ask your doctor about a maximum weight. Doubles tennis might be low-key enough to do, but singles might be too intense. Cycling at an average pace on a stationary bike may be okay, but racing outdoors or mountain biking may be too risky.
  • Try to avoid high-impact activities. These would include gymnastics, water skiing, horseback riding, downhill skiing, hockey, basketball, soccer, scuba diving. Anything that involves a lot of jumping or sharp movements from one direction to another isn't ideal. 
  • Be careful and use common sense. Don't work out if it's super hot or humid or if you have a fever, and be sure to drink lots of water before, during, and after you exercise to stay hydrated. Stop the activity if you experience dizziness, shortness of breath, chest pain, headache, muscle weakness, calf pain or swelling, uterine contractions, or if there is fluid or blood leaking from your vagina.
  • Get new gym clothes. As your body grows during pregnancy, you will likely need to buy larger tops, bottoms, and sports bras, so you can work out comfortably. Yoga pants, which stretch as you get larger, are a popular choice!
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  1. Juhl M, Andersen PK, Olsen J, et al. Physical exercise during pregnancy and the risk of preterm birth: a study within the Danish National Birth Cohort. Am J Epidemiol. 2008;167(7):859-66. doi:10.1093/aje/kwm364

Additional Reading
  • "Heavy exercise miscarriage link." BBC News (2007).
  • "Exercise During Pregnancy." American Congress of Obstetricians and Gynecologists (2011).
  • Madsen, M., T. Jørgensen, M.L. Jensen, M. Juhl, J. Olsen, P.K. Andersen, A-M Nybo Andersen, “Leisure Time Physical Exercise During Pregnancy and the Risk of Miscarriage: A Study Within the Danish National Birth Cohort” BJOG: An International Journal of Obstetrics and Gynaecology (OnlineEarly Articles)

  • American Pregnancy Association, "Exercise Guidelines During Pregnancy." July 2006.