Exercise in pregnancy: what is safe in each trimester

If you trained before you became pregnant, the question is rarely whether you can carry on — it's how much of the programme you get to keep. Movement is recommended in pregnancy rather than merely tolerated, but a session at 34 weeks looks nothing like one at 14. Here's what genuinely changes trimester by trimester, and how to tell when a session is done.

The baseline numbers and how to judge effort

The guidance is fairly consistent: around 150 minutes of moderate activity a week, spread across three to five days, plus two full-body strength sessions. That is the same frame that applies outside pregnancy. What changes is how you dose the intensity.

Heart rate is a poor guide here, because resting pulse climbs by roughly 10 to 20 beats, which makes age-based formulas meaningless. Use the talk test instead: you should be able to finish a full sentence without gulping for air. On a 6-to-20 effort scale that lands around 12 to 14 — working, with something left over.

If you have never trained, pregnancy isn't a reason to avoid starting, but you don't start at 150 minutes. Fifteen minutes of walking or a stationary bike three times a week, adding five minutes each week until you reach about thirty, is a sane on-ramp.

First trimester: the sickness costs more than the training

Up to week 13 nothing shows on the outside while most of the change happens inside. The limiting factor is rarely load. It is nausea, the tiredness that arrives at three in the afternoon, and an appetite with a mind of its own.

Keep the exercises you already do, but stop taking the last set to failure. Sets of 8 to 15 reps with two or three reps left in reserve give you nearly the same result for far less wear. If you're being sick, don't train on an empty stomach: a small meal an hour before and a bottle within reach solves half of it, and how much water you actually need depends on how much you sweat rather than on a fixed figure.

Overheating is the one thing in this stretch that deserves a firm rule. Saunas, hot yoga and midday training outdoors in summer are risk you gain nothing from. A ventilated room, lighter kit and proper drink breaks cover it.

Second trimester: the steadiest stretch

From week 14 to 27 the nausea usually eases, energy returns and the bump doesn't yet interfere with most lifts. This is when a tidy routine is easiest to hold — something like three sessions a week weighted towards the lower body, since your hips and legs carry what's coming.

Two things need adjusting. First, lying flat on your back: from roughly week 16 the uterus can press on the large vein beside the spine, and some women get a drop in blood pressure and feel dizzy. You don't have to bin pressing — set the bench at 15 to 30 degrees and the problem usually disappears. Second, balance: your centre of mass shifts forward, so do single-leg work with a hand on a wall or rack.

Strength work stays. Squats, Romanian deadlifts, rows and presses all still apply, at loads you can handle without holding your breath. This isn't the season for personal bests — spend the technique you built, not the kilos. Protein is the one nutrition item worth watching more closely than before, and the numbers per kilogram of bodyweight beat guesswork.

Third trimester: less load, more movement

From week 28 breathlessness arrives sooner, joints feel looser and your back and pelvis start making themselves known. The goal shifts from progress to maintenance: shorter sets, longer rests. Three sets of 10 to 12 with a moderate weight does the job.

Swaps worth making: a goblet squat to a bench instead of a barbell squat, deadlifts from blocks instead of the floor, standing presses instead of lying ones, cables where the bump gets in the way of a bar. For cardio, walking, the stationary bike and the pool. Water takes away part of the weight you're carrying, which is why swimming often feels better than anything on land.

There is no week at which you must stop. Plenty of women keep moving until labour, just in an increasingly gentle form. Constipation and heavy legs are more common now, and fibre in your daily meals plus regular walking helps far more than any abdominal exercise.

What stays off the list throughout

The list is shorter than most people assume, and it mostly comes down to impact, falls and heat:

• contact sports, and anything where a ball or an opponent can hit your abdomen;
• activities with a high risk of falling: skiing, riding, mountain biking, gymnastics;
• scuba diving, at any stage;
• saunas, hot yoga and long sessions in the heat;
• maximal efforts held with a locked breath;
• exertion above roughly 2,500 metres if you aren't used to altitude.

Running and jumping aren't banned; they belong on the "for as long as it's comfortable" list. Most runners stop somewhere between weeks 20 and 30, because of pressure in the pelvis rather than any danger to the baby.

Pelvic floor and abdominal wall

Pelvic floor work is the one part of the programme that gets added in pregnancy rather than trimmed. The evidence here is among the stronger evidence in this whole area: training it regularly lowers the chance of leaking, both during pregnancy and in the months after. In practice, three sets of 8 to 10 contractions held for 6 to 8 seconds, daily, with as much attention to letting go as to squeezing.

Almost every woman's abdominal muscles separate somewhat by late pregnancy. That is an adaptation, not an injury. Sit-ups and leg raises from your back have no place at that point; forearm planks, dead bugs and rib-cage breathing do the same work without the pressure.

The sign that a movement is too much is visible: the midline of the belly domes into a ridge, you hold your breath to get through it, or you feel a downward push in your pelvis. Take the easier version. Coming back after the birth is its own project that starts with breathing and the pelvic floor — what's safe in that first year with a baby is worth reading before you begin.

When to see a doctor

Ask before you start or continue if you have high blood pressure, placenta praevia, a shortened cervix, a previous preterm birth, a heart or lung condition, or you're carrying twins. That rarely means no exercise at all — it means the programme should be set by someone who has seen your notes.

Stop the session immediately and get in touch if you have:

• bleeding or fluid leaking;
• regular painful contractions;
• breathlessness before you've even started, or chest pain;
• a headache that won't shift, dizziness or fainting;
• pain and swelling in one calf;
• leg weakness that affects your balance.

The short version

• Aim for about 150 minutes of moderate activity a week plus two strength sessions, and judge effort by the talk test, not your heart rate.
• First trimester: same exercise choices, fewer sets to failure, and real attention to nausea and overheating.
• Second: the best window for consistent training; incline the bench instead of lying flat, and lean on technique rather than chasing records.
• Third: maintenance over progress, three sets of 10 to 12, more walking and swimming, and swaps for anything the bump blocks.
• Train the pelvic floor daily; bleeding, chest pain or leaking fluid mean stop and call your doctor.