Exercise During Pregnancy

Contents

1. Earlier advice leaned toward caution
2. Guidance moved toward encouragement
3. The weekly target matches the general one
4. The evidence links exercise to fewer complications
5. Pregnancy changes how the body handles effort
6. Some activities are favored and others flagged
7. Certain symptoms end a session
8. Research is reaching harder training
9. What exercise in pregnancy cannot do

Outside medicine, Candace Cooley is a skier, a cyclist and a runner, and the question at the center of this entry is one pregnant women put plainly: is it safe to exercise while pregnant? For a healthy woman with a normal pregnancy, ACOG’s patient guidance answers that it is safe to continue or to start regular physical activity, after a conversation about it at early prenatal visits.¹ That answer is newer than many people assume.

Earlier advice leaned toward caution

For much of the past generation, the default was restraint. A 6abc parenting column recalls that vigorous exercise in pregnancy was once seen as a danger to the baby and that pregnant women were told to keep their heart rate under 140 beats per minute.⁸ An NPR report from 2017 describes the related belief that a woman who was not already exercising should not begin during pregnancy, a view the researchers it quoted said no longer holds.⁵

Guidance moved toward encouragement

The shift came as observational evidence built up. The 2017 NPR report covered a viewpoint by exercise researchers finding a strong consensus that exercise benefits both mother and fetus.⁵ A follow up NPR segment summarized the same study as concluding that exercise is, in most cases, good for mothers and their babies.⁶ In 2020, ACOG Committee Opinion 804 replaced its 2015 predecessor and told obstetric care providers to encourage patients to continue or begin exercising, describing the risks as minimal for most women.²

The weekly target matches the general one

Current guidance asks roughly what it asks of everyone. ACOG sets a goal of at least 150 minutes of moderate aerobic activity a week, defining moderate as enough to raise the heart rate and break a sweat while still being able to talk, though not sing.¹ A Minnesota Department of Health handout cites the same federal figure and adds two days of muscle strengthening.⁹ Uptake lags: NPR’s Life Kit reports that only 10 to 15 percent of pregnant women meet the recommendation.³

Figure

Weekly activity in current patient guidance

of moderate intensity aerobic activity every week

150 minutes

a session on 5 days of the week, as one way to reach it

30 minutes

The evidence links exercise to fewer complications

Committee Opinion 804 cites observational studies showing less gestational diabetes, fewer cesarean births and operative vaginal deliveries, and shorter postpartum recovery among women who exercise.² ACOG’s patient page adds reduced back pain, eased constipation and healthy weight gain.¹ A University of Alberta researcher interviewed by Life Kit described a 40 percent reduction in the odds of preeclampsia, gestational hypertension and gestational diabetes.³ Benefits continue into the postpartum period, where activity can help prevent depressive disorders.² The same researcher told Life Kit that babies of active mothers have a lower later risk of obesity and diabetes.³

Pregnancy changes how the body handles effort

The physiology explains the adjustments guidance recommends. Hormones loosen the ligaments around joints, and extra weight in front shifts the center of gravity, raising the chance of a fall.¹ A clinician summary from The ObG Project notes that cardiac output rises by 35 to 45 percent in the second and third trimesters and that minute ventilation increases by about half, with less pulmonary reserve and a slight impairment of anaerobic exercise.⁷ Heat and posture matter too. ACOG advises against becoming overheated, especially in the first trimester, and against long stretches lying flat on the back, because the uterus can press on a large vein returning blood to the heart and briefly lower blood pressure.¹ For gauging intensity, The ObG Project points to perceived exertion and the talk test rather than a fixed heart rate.⁷

Some activities are favored and others flagged

ACOG lists walking, swimming, stationary cycling and modified yoga or Pilates among the safest choices. It flags contact sports, activities with a high chance of falling, such as downhill skiing and off road cycling, hot yoga, scuba diving, and exertion above 6,000 feet for women who do not already live at altitude, a point taken up in altitude acclimatization.¹

Figure

Activities in ACOG patient guidance

	Listed among the safest	Listed to avoid
Cardio	Brisk walking	Contact sports such as ice hockey and soccer
Water	Swimming and water workouts	Scuba diving
Cycling	Stationary bicycling	Off road cycling
Mind and body	Modified yoga and Pilates	Hot yoga or hot Pilates

Running sits in between. Five experts polled by The Conversation all judged it acceptable for uncomplicated pregnancies, and one cited a 2018 study of 1,293 runners in which running did not appear to affect gestational age or birthweight.⁴

Certain symptoms end a session

Guidance pairs encouragement with a list of reasons to stop. ACOG names vaginal bleeding, dizziness or faintness, shortness of breath before exercise, chest pain, headache, muscle weakness, calf pain or swelling, and regular painful contractions as signs to stop and contact an obstetrician.¹ The Minnesota handout adds that any activity causing discomfort should be discontinued.⁹

Research is reaching harder training

The newest work looks past moderate exercise. Outside magazine reported on a 2023 study in which 15 pregnant volunteers did intervals above 90 percent of predicted maximum heart rate with no relevant differences in fetal or maternal measures compared with moderate cycling, and on surveys of weightlifters and climbers who trained through pregnancy.¹⁰ The researchers behind that work are helping shape revised international guidelines for pregnant athletes due in 2027, built around weighing risks and benefits case by case rather than fixed rules.¹⁰ Related questions for active women appear under sports medicine and the woman athlete.

What exercise in pregnancy cannot do

Exercise lowers the odds of several complications; it does not remove them, and it cannot stand in for prenatal care. Its upper limits remain unknown: The ObG Project calls the safety literature on elite athletes limited, and a kinesiologist quoted by NPR said the ceiling for trained athletes, and the ideal amount for any individual, are not known.⁷⁵ Nor can guidelines fit every life; a sports scholar in The Conversation noted that ideas about exercise in pregnancy keep changing and that not every woman has the means or desire to train.⁴ How any one pregnancy should be paced is a decision for the woman and her own clinician.