Does running increase the risk of miscarriage in the first trimester?

Running During First Trimester Does Not Increase Miscarriage Risk

Regular physical activity, including running, does not increase the risk of miscarriage in the first trimester for healthy pregnant women without contraindications. 1

Evidence on Exercise and Miscarriage Risk

• A recent meta-analysis demonstrated no increased odds of miscarriage or perinatal mortality in otherwise healthy pregnant women who exercised compared with those who did not 1
• The 2019 Canadian Guidelines for Physical Activity throughout Pregnancy explicitly state that physical activity is not associated with miscarriage, stillbirth, or neonatal death 1
• A 2023 systematic review and meta-analysis found no significant association between exercise during pregnancy and the occurrence of miscarriage (Risk Ratio = 0.83,95% CI = 0.49-1.41) 2

Benefits of Exercise During Pregnancy

• Regular prenatal physical activity is associated with numerous health benefits, including:
  • 38% reduction in gestational diabetes mellitus 1
  • 41% reduction in pre-eclampsia 1
  • 39% reduction in gestational hypertension 1
  • 67% reduction in prenatal depression 1
  • 39% reduction in macrosomia (large babies) 1

Exercise Recommendations During Pregnancy

• Pregnant women should accumulate at least 150 minutes of moderate-intensity physical activity each week 1
• Physical activity should be accumulated over a minimum of 3 days per week, though daily activity is encouraged 1
• A variety of aerobic and resistance training activities is recommended for greater benefits 1

Important Considerations for Running During First Trimester

• While running is generally safe, consider these safety precautions:
  • Avoid physical activity in excessive heat, especially with high humidity 1, 3
  • Maintain adequate nutrition and hydration—drink water before, during, and after physical activity 1
  • Know when to stop exercise (persistent shortness of breath, severe chest pain, regular painful contractions, vaginal bleeding, persistent dizziness) 1

Special Populations

• Women with recurrent pregnancy loss (defined as three or more consecutive losses before 24 weeks):
  • It is unlikely that regular physical activity within guidelines would increase the risk of loss 1
  • Exercise may actually benefit factors that increase miscarriage risk, such as insulin resistance and obesity 1

Conflicting Evidence to Consider

• One older study (2007) suggested a potential association between high-impact exercise and increased risk of miscarriage, particularly with more than 7 hours of exercise per week 4
• However, this study had methodological limitations including potential recall bias from retrospective data collection 4
• More recent and higher-quality evidence contradicts these findings, showing no increased risk 1, 2

Conclusion for Clinical Practice

• Running during the first trimester is safe for women without contraindications to exercise 1
• Women who were previously active can continue their regular physical activity throughout pregnancy, including running 1
• Previously inactive women should start gradually and progress toward meeting the guidelines 1
• Women may need to modify their activity as pregnancy progresses due to physiological changes 1