Exercise During Pregnancy: What Is Safe, What to Avoid, and Why It Matters

Staying physically active during pregnancy is one of the most evidence-backed things you can do for your health and your baby's development. Both the NHS and the American College of Obstetricians and Gynecologists (ACOG) recommend that pregnant women without obstetric or medical complications aim for at least 150 minutes of moderate-intensity aerobic activity each week. That breaks down to around 30 minutes on most days — a target that is achievable for the vast majority of healthy pregnancies.

This article covers the benefits in detail, what activities are safe, what to avoid and the clinical reasoning behind each restriction, how to adjust your routine across each trimester, why pelvic floor training matters, and the warning signs that mean you should stop immediately and contact a midwife or doctor.

Fact-Checked & Transparent: This article is fact-checked against current CDC, WHO, ACOG, and NHS guidelines. All health information is based on authoritative medical sources. Last verified: June 2026.

⚠️ MEDICAL DISCLAIMER

This article is educational information only. It is NOT a substitute for professional medical advice, diagnosis, or treatment.

Always consult your pediatrician or healthcare provider before making any medical decisions for your baby or child. Every baby is unique, and professional medical guidance is essential.

In case of emergency, call 911 or your local emergency number.

Why Exercise During Pregnancy Matters

The research base here is strong. Regular moderate exercise during pregnancy:

• Reduces the risk of gestational diabetes by up to 30%, according to a 2017 meta-analysis published in the British Journal of Sports Medicine
• Lowers blood pressure and reduces the risk of pre-eclampsia
• Reduces the severity of pregnancy-related back pain
• Improves sleep quality, which tends to deteriorate in the second and third trimesters
• Reduces the risk of excessive gestational weight gain
• Supports mental health — evidence consistently links regular physical activity with lower rates of antenatal depression and anxiety
• May reduce the duration of labour in some studies, though the evidence here is less consistent

The NHS and ACOG are in close agreement: the message is not to become an elite athlete, but to avoid prolonged inactivity. If you were active before pregnancy, you can generally continue what you were doing with modifications as pregnancy progresses. If you were not exercising regularly before pregnancy, now is a reasonable time to start gently — beginning with walking or swimming rather than high-intensity interval training.

What Counts as Safe Exercise in Pregnancy

Walking

Walking is accessible, free, low-impact, and safe throughout all three trimesters. Even a brisk 30-minute walk on most days meets the NHS and ACOG weekly activity target. As your bump grows, you may need to shorten the duration and reduce pace — that is fine.

Swimming and Aqua Aerobics

Water supports your increasing body weight, reducing strain on joints and the lower back. Swimming is particularly useful in the third trimester when many other forms of exercise become uncomfortable. Aqua aerobics classes designed for pregnancy are widely available and give the added benefit of social support. The one caution: avoid very warm pools (above 34°C).

Stationary Cycling

Cycling on a stationary bike is safe because it removes the fall risk associated with road cycling. It provides cardiovascular benefit without jarring the joints. As your bump grows and your centre of gravity shifts, road cycling carries an increasing risk of falls, which is why stationary is the preferred option from around 20 weeks onwards.

Pregnancy Yoga and Pilates

Both yoga and Pilates classes specifically designed for pregnancy focus on breathing, posture, core stability (protecting rather than loading the rectus abdominis), and relaxation techniques. They are safe throughout pregnancy and are genuinely useful preparation for labour. Check that your instructor is trained in prenatal exercise.

Strength Training at Reduced Intensity

Light to moderate strength training is safe during pregnancy when performed with attention to form. The key modifications: reduce the weight you were previously using, avoid breath-holding (the Valsalva manoeuvre), avoid exercises that place the load directly over the abdomen, and avoid lying flat on your back from around 16 weeks onwards. ACOG notes that resistance training can safely be continued throughout pregnancy with appropriate adjustments.

Low-Impact Aerobics

Pregnancy-specific aerobics classes (and many classes labelled "low-impact") are safe options. They maintain cardiovascular fitness without the joint stress of high-impact activity.

What to Avoid — and Why

Contact Sports

Sports with a significant risk of abdominal impact — including ice hockey, football, basketball, martial arts, and horse riding — should be avoided during pregnancy. The risk is abdominal trauma, which can cause placental abruption. This is not about overprotection; it is about a specific, serious mechanism of harm.

Hot Yoga and Sauna Use

Core body temperature above 38°C in the first trimester carries a teratogenic risk — elevated maternal temperature is associated with neural tube defects and cardiac abnormalities in the developing embryo. Hot yoga rooms typically operate at 37–41°C. The NHS advises pregnant women to avoid saunas, steam rooms, and hot tubs, particularly in the first trimester. Standard yoga at room temperature remains safe.

Lying Flat on Your Back from 28 Weeks

The inferior vena cava — the large vein returning blood from the lower body to the heart — runs along the right side of the spine. From around 28 weeks, the weight of the uterus can compress this vein when you lie on your back, reducing the volume of blood returning to the heart. This can cause a sudden drop in blood pressure, dizziness, nausea, and, in some cases, a temporary reduction in blood flow to the placenta. This is why exercises performed lying flat on your back (supine exercises) should be modified or substituted from this point. Many practitioners apply a precautionary modification from around 16 weeks onwards.

Scuba Diving

Scuba diving is contraindicated throughout pregnancy. No safe depth for a fetus has been established. Decompression sickness poses particular risk because the fetal circulation cannot off-gas nitrogen bubbles the way an adult's can.

High-Altitude Exercise

If you are at altitude above approximately 2,500 metres and are not acclimatised, exercise can reduce oxygen delivery to the fetus. Walking at moderate altitude on a holiday is generally not a concern; intensive training at high altitude is a different matter.

The Talk Test

A simple, clinically validated way to gauge exercise intensity during pregnancy is the talk test. You should be able to hold a conversation during exercise. If you are too breathless to speak in full sentences, the intensity is too high. Reduce pace or intensity until you can speak comfortably. This keeps you in the moderate-intensity zone that the NHS and ACOG recommend.

Trimester-by-Trimester Modifications

First Trimester (Weeks 1–12)

Fatigue and nausea are the main challenges in the first trimester. Many women find that their usual exercise routine becomes harder simply because they are exhausted. This is normal — listen to your body. On days when nausea is severe, rest is more appropriate than forcing a workout. On better days, maintain activity if you can.

The absolute caution in the first trimester is body temperature — avoid hot environments. Otherwise, this is the trimester with the fewest structural restrictions. Your centre of gravity has not yet shifted, your bump is not yet affecting movement, and most activities are accessible.

If you have a history of recurrent miscarriage or have been told you have a threatened miscarriage, speak to your midwife before exercising. For the majority of pregnancies, there is no evidence that moderate exercise increases miscarriage risk.

Second Trimester (Weeks 13–28)

For many women, the second trimester is the most comfortable period for exercise. Nausea typically eases, energy often returns, and the bump has not yet grown large enough to significantly restrict movement.

From around 16 weeks, begin modifying exercises performed flat on your back. Replace them with side-lying, seated, or standing alternatives. Avoid exercises that load the midline of the abdomen directly (such as full sit-ups or crunches), as these can worsen diastasis recti — the separation of the two halves of the rectus abdominis muscle. Pregnancy Pilates instructors are trained to work around this.

Continue the talk test. As your cardiovascular demands increase, you may find that your previous pace feels harder — this is expected.

Third Trimester (Weeks 28–40)

Your centre of gravity shifts forward significantly as the bump grows, increasing the risk of falls and placing more strain on the lower back and pelvis. Reduce intensity. Choose lower-impact options. Swimming becomes particularly comfortable in this trimester because the water supports the weight of your bump.

Avoid supine exercises (flat on your back) entirely from 28 weeks. Pelvic girdle pain affects a significant minority of women in the third trimester and may limit what feels comfortable — work within that. Even gentle walking and stretching maintain cardiovascular conditioning and support mental health in the final weeks.

Pelvic Floor Exercises: Non-Negotiable at Every Stage

Pelvic floor training is often framed as optional or as an afterthought, but both the NHS and ACOG are clear: pelvic floor exercises should be performed daily throughout pregnancy and continued postpartum.

The pelvic floor muscles support the bladder, bowel, and uterus. Pregnancy places sustained pressure on these muscles for months, and labour (particularly vaginal delivery) can stretch and weaken them significantly. Regular training reduces the risk of urinary incontinence during and after pregnancy, reduces the risk of pelvic organ prolapse, and supports recovery postpartum.

The basic technique: identify the muscles you would use to stop the flow of urine mid-stream (do not actually do this while urinating — it is just a way to locate the muscles). Contract, hold for 8–10 seconds, then fully relax. Aim for 8–12 contractions, three times a day. Both quick flicks and sustained holds have value. If you are unsure whether you are performing them correctly, a women's health physiotherapist can assess and guide you.

Warning Signs to Stop Immediately

Stop exercising and contact your midwife or doctor promptly if you experience any of the following during or after exercise:

• Vaginal bleeding or fluid leaking
• Chest pain or palpitations
• Severe shortness of breath that does not resolve quickly with rest
• Calf pain or swelling (potential DVT)
• Severe headache
• Dizziness or feeling faint
• Regular painful contractions
• Significant reduction in fetal movement

These symptoms are not specifically caused by exercise, but they are warning signs that need clinical assessment regardless of what triggered them. Do not wait to see if they settle.

Returning to Exercise After Birth

Exercise after birth is covered in detail in a separate article. The short version: recovery timelines differ significantly between vaginal birth and caesarean section, and pelvic floor recovery should take priority over returning to high-impact activity. Most guidelines suggest waiting until after the six-week postnatal check before resuming anything more than walking and pelvic floor exercises — though the six-week check should not be treated as an automatic green light for running or heavy lifting.

Frequently Asked Questions

Is it safe to start exercising for the first time during pregnancy?

Yes, for most healthy pregnancies. Begin with low-impact activity such as walking or swimming. Start at 15–20 minutes and build gradually towards the 150-minute weekly target. Avoid high-intensity activity if you have been sedentary. Let your midwife know you are starting to exercise, particularly if you have any pregnancy complications.

Can I run during pregnancy?

Running is safe to continue if you were running regularly before pregnancy. As the bump grows, your gait changes and the impact on your pelvic floor increases. Many runners transition to jogging, then to a run-walk approach, then to walking as pregnancy progresses. Listen to your body, maintain the talk test, and pay close attention to any pelvic floor symptoms such as leaking urine — if these occur, reduce impact and see a women's health physiotherapist.

Is it safe to lift weights when pregnant?

Light to moderate strength training is safe throughout pregnancy with the modifications described above. Avoid maximal lifts, breath-holding, and exercises that load the abdomen directly or require you to lie flat on your back. Use a weight that allows you to complete your sets without straining.

Can exercise cause miscarriage?

There is no good evidence that moderate exercise causes miscarriage in otherwise healthy pregnancies. The vast majority of early miscarriages are caused by chromosomal abnormalities in the embryo, not by maternal activity. If you have been told your pregnancy is at risk, discuss the appropriate level of activity with your healthcare provider.

Does exercise help with pregnancy back pain?

Yes. Strengthening the muscles around the lower back and pelvis — including through pregnancy yoga, Pilates, and swimming — is one of the most effective strategies for managing pregnancy-related back pain. A women's health physiotherapist can assess posture and provide targeted exercises if back pain is significant.

What exercise is best in the third trimester?

Swimming is widely regarded as the most comfortable form of exercise in the third trimester because the water supports the weight of the bump. Walking, stationary cycling, and pregnancy yoga or Pilates are also well-tolerated. Intensity should be reduced compared to earlier in pregnancy, and any exercise that requires lying flat on the back should be avoided.

Key Takeaways

• The NHS and ACOG both recommend 150 minutes of moderate-intensity activity per week during pregnancy — the equivalent of 30 minutes on most days
• Regular exercise reduces gestational diabetes risk by up to 30%, lowers blood pressure, reduces back pain, improves sleep, and supports mental health
• Safe activities include walking, swimming, stationary cycling, pregnancy yoga and Pilates, low-impact aerobics, and moderate strength training
• Avoid contact sports (abdominal trauma risk), hot yoga and saunas over 38°C (teratogenic risk in first trimester), lying flat on your back from 28 weeks (vena cava compression), and scuba diving (no safe depth established)
• Use the talk test: if you cannot hold a conversation, reduce intensity
• Modify exercise each trimester — first trimester focus is on avoiding heat; second trimester is the most comfortable period; third trimester requires reduced intensity and fall-risk awareness
• Pelvic floor exercises should be performed daily throughout pregnancy and postpartum — not optional
• Stop immediately and contact your midwife if you experience vaginal bleeding, chest pain, severe breathlessness, calf pain, dizziness, contractions, or reduced fetal movement

📋 SOURCES & FACT-CHECKING

This article is compiled and verified against these authoritative sources: - CDC (Centers for Disease Control & Prevention) - WHO (World Health Organization) - ACOG (American College of Obstetricians and Gynecologists) - NHS (National Health Service) - AAP (American Academy of Pediatrics)

Last verified: June 2026

Educational content only. Always consult your pediatrician for medical decisions.

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