Exercising During Pregnancy — What Is Safe and What to Avoid
Pregnancy is not a reason to stop exercising — for most women, it is a reason to keep going. The American College of Obstetricians and Gynecologists (ACOG) recommends that women without complications do at least 150 minutes of moderate aerobic activity a week during pregnancy, and the evidence links it to lower rates of gestational diabetes, less back pain, better mood and easier labour.
But pregnancy changes the rules: some exercises become unsafe, intensity needs adjusting, and there are warning signs that mean stop and seek care. This guide covers what is safe in each trimester, what to avoid, and when to talk to your clinician — because the right exercise in pregnancy is genuinely beneficial, and the wrong exercise, or exercising against medical advice, is not worth the risk.
Use the calculator
Start with the numbers: try our heart rate zone calculator to work out your own figures before applying anything on this page. The worked examples below use round numbers so you can follow the maths; the calculator uses your real weight, height, age and goal.
Related reading: heart rate zone calculator, TDEE calculator, How to Start Walking for Fitness, Exercise for Seniors, full guides section.
The formula behind pregnancy exercise
The key number in pregnancy exercise is not a calorie figure but an intensity guide. ACOG recommends moderate intensity, defined as activity where you can talk but not sing — the 'talk test' — and the older 'keep heart rate below 140 beats per minute' rule has been retired, because heart-rate responses vary too much in pregnancy. For those who want a number, the Borg rating of perceived exertion (RPE) scale of 6–20 is the practical tool: moderate intensity is about 12–14, or 'somewhat hard'. The energy side still uses the Mifflin-St Jeor equation (Mifflin et al., 1990) — 10 × weight (kg) + 6.25 × height (cm) − 5 × age, minus 161 for women — but pregnancy adds energy needs: roughly 0 extra kcal/day in the first trimester, about 340 kcal/day in the second, and about 450 kcal/day in the third (Institute of Medicine, 2009). These are population averages, and individual needs vary with pre-pregnancy weight, activity and medical conditions — which is why calorie targets in pregnancy belong to a clinician, not a calculator. The safety floors of 1,200 kcal/day for women still apply as an absolute minimum, and in pregnancy the practical floor is higher, set by your clinician.
The key points
Walking, swimming and stationary cycling are the safest choices. Low-impact aerobic exercise is the backbone of pregnancy activity: walking, swimming, water aerobics, stationary cycling and low-impact aerobics all raise fitness without stressing the joints, which loosen during pregnancy under the hormone relaxin. Swimming is especially useful late in pregnancy because the water supports the extra weight. Aim for 150 minutes a week of moderate activity, broken into sessions of 20–30 minutes — and if you were inactive before pregnancy, start with 10 minutes a day and build gradually.
Strength training is fine — with modifications. Moderate strength training is safe and useful in pregnancy: it supports posture, reduces back pain and prepares the body for labour. Use lighter weights and higher repetitions (12–15 reps), avoid holding your breath and straining (the Valsalva manoeuvre), avoid heavy overhead lifting, and stop any exercise that causes pain or dizziness. Resistance bands and bodyweight exercises are ideal. Avoid lying flat on your back after the first trimester, because the weight of the uterus can compress a major vein and reduce blood flow.
Pelvic floor exercises matter more than crunches. Pelvic floor (Kegel) exercises — tightening the muscles you would use to stop urinating, holding for a few seconds, and releasing — reduce urinary incontinence during and after pregnancy, and they are recommended by ACOG and the UK's NICE guidance. Do them daily: three sets of 8–12 slow contractions, plus quick flicks. Traditional crunches and sit-ups, by contrast, should be avoided once the abdomen is prominent, and any exercise that causes the abdomen to 'dome' along the midline (coning) should be stopped.
Avoid contact, falling and overheating. Sports with a risk of falling or abdominal impact — horse riding, skiing, contact sports, gymnastics, cycling on roads — should be avoided during pregnancy. So should hot yoga and exercising in very hot conditions, because overheating in the first trimester is a recognised risk. Scuba diving is contraindicated throughout pregnancy. Exercise in a cool environment, drink water, wear loose clothing, and stop if you feel dizzy, overheated or unwell.
Know the warning signs that mean stop. ACOG lists clear stop signals: vaginal bleeding, regular painful contractions, fluid leaking from the vagina, breathlessness before exercise, dizziness, headache, chest pain, muscle weakness affecting balance, or calf pain or swelling. If any of these occur during or after exercise, stop and contact your clinician the same day — sooner if bleeding, fluid loss or contractions occur. These are not 'push through it' symptoms; they are the body's way of saying the session is over.
After birth, rebuild gradually. The postnatal return to exercise is gradual: pelvic floor exercises can restart within days, walking as soon as you feel able, and more vigorous exercise after the postnatal check at about six weeks (sooner if your clinician advises). Breastfeeding mothers need extra fluids and energy, and should not restrict calories aggressively. The goal in the first months is recovery and rebuilding, not returning to pre-pregnancy fitness on a deadline.
At a glance
| Trimester | Safe activity | Avoid | Notes |
|---|---|---|---|
| First (weeks 1–13) | Walking, swimming, light strength, yoga | Contact sports, hot yoga, scuba | Start with 10 min/day if previously inactive |
| Second (weeks 14–27) | As above + prenatal classes, cycling | Lying flat on your back, heavy lifting | Energy needs rise ~340 kcal/day |
| Third (weeks 28–40) | Walking, swimming, pelvic floor, gentle stretching | Balance-risk sports, overheating | Shorter sessions, stop if breathless |
| Postnatal | Pelvic floor, walking, gradual rebuild | Vigorous exercise before the 6-week check | Rebuild over weeks, not days |
A worked example: a pregnancy exercise week
Take a 30-year-old woman, 65 kg, 165 cm, in her second trimester, who walked regularly before pregnancy. Her BMR by Mifflin-St Jeor is 10 × 65 + 6.25 × 165 − 5 × 30 − 161 = 650 + 1,031 − 150 − 161 = 1,370 kcal/day, and with the second-trimester addition of about 340 kcal/day her maintenance is roughly 2,100–2,400 kcal/day depending on activity — but this is a reference point for her clinician, not a diet target: pregnancy is not a time to restrict calories, and any weight-management question in pregnancy belongs to a clinician. Her week: five 30-minute walks (150 minutes of moderate activity, talk-test intensity, RPE 12–14), two 20-minute strength sessions with resistance bands (squats, rows, glute bridges, 12–15 reps, no lying flat on her back, no breath-holding), and daily pelvic floor exercises (3 sets of 10 slow contractions). She exercises in the morning when it is cool, drinks water, and stops if she feels dizzy or breathless. If she was previously inactive, the same week would start at half the volume and build over a month. The expected benefits — less back pain, better mood, lower gestational diabetes risk — are the outcomes the ACOG guidance is built on.
How to use this guide
Talk to your clinician before starting or continuing an exercise programme in pregnancy, especially if you have any medical condition, a high-risk pregnancy, or you were inactive before conceiving. Then build the week around the safe list: walking or swimming most days, strength twice a week, pelvic floor daily. Use the talk test rather than a heart-rate number to judge intensity, and keep a simple note of how each session felt — energy, breathlessness, any pain — so you can discuss it at your next appointment. As pregnancy progresses, expect to shorten sessions and reduce intensity; that is adaptation, not failure. And learn the stop signals by heart, because the one piece of advice that matters most in this guide is knowing when to stop and call for care.
What this guide does NOT tell you
This guide is general information for women with uncomplicated pregnancies; it does not replace your clinician's advice, and it does not apply to high-risk pregnancies, multiple pregnancies, placenta praevia, pre-eclampsia, or any condition your clinician has flagged — in those cases, follow your clinician's specific instructions, which override everything here. The numbers on this page — 150 minutes a week, RPE 12–14, 340 and 450 kcal/day additions — are population guidance from ACOG and the Institute of Medicine, not individual prescriptions, and they do not account for your pre-pregnancy weight, medical history or medicines. This guide does not diagnose anything and does not cover labour, birth or postnatal complications. If you experience any of the warning signs listed above, stop exercising and contact your clinician the same day. And a final limit: no calorie target on this page should be used as a diet plan in pregnancy — energy needs in pregnancy are set by your clinician, and restrictive dieting in pregnancy is unsafe.
Frequently asked questions
How much exercise should I do during pregnancy?
ACOG recommends at least 150 minutes of moderate aerobic activity a week for women without complications, in sessions of 20–30 minutes. If you were inactive before pregnancy, start with 10 minutes a day and build gradually. Use the talk test — you should be able to talk but not sing — rather than a heart-rate target.
Can I lift weights while pregnant?
Yes, moderate strength training is safe and useful, with modifications: lighter weights, 12–15 reps, no breath-holding and straining, no heavy overhead lifting, and no lying flat on your back after the first trimester. Resistance bands and bodyweight exercises are ideal. Stop any exercise that causes pain or dizziness.
What exercises should I avoid in pregnancy?
Contact sports, sports with a fall risk (horse riding, skiing, gymnastics), road cycling, hot yoga, scuba diving, and any exercise lying flat on your back after the first trimester. Also avoid exercising in very hot conditions. Walking, swimming, stationary cycling and prenatal classes are the safest choices.
What are pelvic floor exercises and why do they matter?
Pelvic floor (Kegel) exercises strengthen the muscles supporting the bladder and uterus, and they reduce urinary incontinence during and after pregnancy. Tighten the muscles you would use to stop urinating, hold for a few seconds, release — three sets of 8–12 slow contractions daily, plus quick flicks. They are recommended by ACOG and NICE.
When should I stop exercising and seek help?
Stop and contact your clinician the same day if you have vaginal bleeding, regular painful contractions, fluid leaking, breathlessness before exercise, dizziness, headache, chest pain, muscle weakness affecting balance, or calf pain or swelling. Bleeding, fluid loss or contractions need urgent attention.
When can I exercise again after giving birth?
Pelvic floor exercises can restart within days and walking as soon as you feel able. More vigorous exercise usually waits until the postnatal check at about six weeks, sooner if your clinician advises. Rebuild gradually over weeks — the goal is recovery, not a deadline.
Estimates only, not medical advice. Minimum safe intakes: 1,200 kcal/day women, 1,500 kcal/day men — consult a healthcare professional before a very-low-calorie diet.