Is it safe to participate in a half marathon during the first trimester of pregnancy?

From the Guidelines

It is generally not recommended to participate in a half marathon during the first trimester of pregnancy without consulting a healthcare provider first. While moderate exercise is beneficial during pregnancy, a half marathon is a significant physical challenge that may pose risks to both maternal and fetal wellbeing 1. The 2019 Canadian Guideline for Physical Activity throughout Pregnancy recommends that pregnant women accumulate at least 150 minutes of moderate-intensity physical activity per week, but it does not specifically address long-distance running 1. The World Health Organization 2020 guidelines on physical activity and sedentary behaviour also emphasize the importance of consulting a healthcare provider before engaging in physical activity during pregnancy, especially if it involves high-intensity or high-risk activities 1.

Some key considerations for pregnant women who want to engage in physical activity include:

• Avoiding physical activity during excessive heat or high humidity 1
• Staying hydrated by drinking water before, during, and after physical activity 1
• Avoiding activities that involve physical contact, pose a high risk of falling, or may limit oxygenation 1
• Listening to their body's signals and stopping if they experience any discomfort or danger signs 1

If a pregnant woman is already a regular runner and has no complications, her doctor might approve continuing with long-distance running, but with important modifications, such as:

• Maintaining a conversational pace rather than pushing for speed
• Wearing supportive footwear and a proper sports bra
• Listening carefully to their body's signals to stop if they experience dizziness, shortness of breath, vaginal bleeding, or contractions 1

Ultimately, the decision to participate in a half marathon during the first trimester of pregnancy should be made in consultation with a healthcare provider, taking into account the individual woman's health status, pregnancy complications, and overall wellbeing 1.

From the Research

Safety of Participating in a Half Marathon During the First Trimester of Pregnancy

• The American College of Obstetricians and Gynecologists emphasizes that physical activity in pregnancy has minimal risk 2.
• Women who exercised regularly before pregnancy can continue and engage in moderate to strenuous activities, although information on strenuous activities in pregnancy is still limited 2.
• Regular physical exercise during pregnancy is associated with numerous benefits, including preventing gestational diabetes, excessive gestational weight gain, and hypertensive disorders 3.
• Exercise is not related to an increased risk of maternal or perinatal adverse outcomes, and compliance with current guidelines is sufficient to achieve the main benefits 3.
• The type and intensity of exercise should be based on the woman's previous fitness level, medical history, and characteristics of the ongoing pregnancy 3, 4, 5.
• Women with uncomplicated pregnancies should be encouraged to engage in aerobic and strength-conditioning exercises before, during, and after pregnancy 4.
• An exercise program that leads to an eventual goal of moderate-intensity exercise for at least 20-30 minutes per day on most or all days of the week should be developed with the patient and adjusted as medically indicated 4.
• Moderate- and high-intensity exercise in normal pregnancies is safe for the developing fetus and clearly has several important benefits 6.

Considerations for Exercise During the First Trimester

• Physical exercise is recommended for all healthy pregnant women, and regular practice can provide many physical and psychological benefits 5.
• However, few pregnant women engage in this practice, and many still have fears and doubts about the safety of exercise 5.
• The advantages of an active and healthy lifestyle should be reinforced during and after gestation, as pregnancy is an appropriate period to introduce new habits 5.
• Health professionals who care for pregnant women should discuss potential health benefits and harms of exercise 6.
• With proper attention to risk stratification and surveillance, exercise is safe for the mother and fetus 6.