For many expectant parents, exercising during pregnancy can bring about questions and anxiety, particularly concerning the risk of miscarriage. It is a common concern whether physical activity might somehow jeopardize the developing pregnancy. For most healthy individuals experiencing a normal pregnancy, however, engaging in moderate exercise is considered safe and offers numerous benefits for both the pregnant individual and the fetus.
Understanding Miscarriage and Its Causes
A miscarriage is defined as the loss of a pregnancy before 20 weeks of gestation. The majority of these losses, approximately 80%, occur within the first trimester (the initial 12 to 13 weeks). Miscarriages are far more common than many people realize, affecting about 1 in 8 known pregnancies.
The primary cause of most miscarriages is chromosomal abnormalities in the developing fetus. These abnormalities occur when the fertilized egg has an incorrect number of chromosomes or errors happen during the cell division process as the embryo grows. This is often a random event, not typically caused by anything the pregnant individual did or did not do. Other factors that can contribute to miscarriage include health conditions like uncontrolled diabetes, infections, hormonal imbalances, or issues with the uterus or cervix. Maternal age also plays a role, with the risk of miscarriage increasing for individuals over 35.
Exercise and Miscarriage Risk: What the Science Says
The scientific consensus largely indicates that moderate-intensity exercise does not increase the risk of miscarriage in healthy pregnancies. Fear of harm to the baby, including miscarriage, is often a barrier to physical activity during pregnancy, but research, including systematic reviews and meta-analyses, has specifically investigated this relationship.
One comprehensive systematic review and meta-analysis, including thirteen randomized clinical trials and data from 3728 pregnant women, found no significant association between exercise during pregnancy and miscarriage. The findings showed no increased risk of miscarriage in those who engaged in low- to moderate-intensity exercise compared to those who did not exercise. This evidence supports the recommendation that pregnant individuals without contraindications can safely exercise throughout their pregnancy. While some older studies, such as one from 2007 involving over 90,000 pregnant women, suggested a potential link between vigorous exercise (like jogging or ball games for more than seven hours a week between weeks 11 and 14) and an increased miscarriage risk, the overall and more recent evidence points to the safety of moderate activity. Organizations like the American College of Obstetricians and Gynecologists (ACOG) advise that physical activity does not increase miscarriage risk for healthy individuals with normal pregnancies.
Safe Exercise Practices During Pregnancy
Engaging in safe exercise throughout pregnancy offers numerous benefits, from reducing back pain and easing constipation to potentially decreasing the risk of gestational diabetes and preeclampsia. The Centers for Disease Control and Prevention (CDC) and ACOG recommend that healthy pregnant individuals aim for at least 150 minutes of moderate-intensity aerobic activity each week. This can be broken down into shorter sessions, such as 30-minute workouts on five days, or even 10-minute segments spread throughout the day.
Moderate intensity means you are active enough to raise your heart rate and start sweating, but still able to carry on a conversation. If you were active before pregnancy, you can generally continue your routine with healthcare provider approval, possibly with modifications as your body changes. For those new to exercise, starting slowly with activities like brisk walking is advisable, gradually increasing duration and intensity. Staying well-hydrated by drinking plenty of water before, during, and after exercise is also important to prevent overheating.
Specific exercises considered safe include:
- Brisk walking
- Swimming and water workouts
- Stationary cycling
- Prenatal yoga
- Pilates
These activities are gentle on joints, provide a full-body workout, and can be continued until birth. Strength training with light weights is also safe and can help strengthen muscles supporting the back, pelvis, and core, which may reduce discomfort and prepare the body for labor. Listening to your body and modifying exercises as your pregnancy progresses is important.
Exercises to Avoid and Warning Signs
While exercise is encouraged, certain activities should be avoided during pregnancy due to increased risk. Contact sports (e.g., soccer, basketball, boxing, ice hockey) and activities with a high risk of falling (e.g., downhill skiing, horseback riding, gymnastics) should be avoided to prevent abdominal trauma or injury. Scuba diving is also not recommended due to pressure changes. Activities involving lying flat on your back should be avoided after the first trimester (typically after 12 weeks), as the growing uterus can compress major blood vessels, potentially restricting blood flow to you and the baby.
Exercising in hot or humid conditions, or participating in hot yoga or hot Pilates, should also be avoided to prevent overheating. Be aware of warning signs that indicate you should stop exercising immediately and seek medical attention. These include:
- Vaginal bleeding
- Dizziness or feeling faint
- Shortness of breath that is more severe than usual
- Chest pain
- Calf pain or swelling
- Regular painful contractions
If any of these symptoms occur, contact your healthcare provider promptly.