Training through pregnancy: what is safe in each trimester

If you trained before you were pregnant, the first question is usually the same one: how much of it can you keep. Most of it, as it turns out — but the goal shifts. For the next nine months you are not chasing numbers, you are holding on to strength, fitness and body control, both of which matter during labour and in the months that follow.

What holds true in all three trimesters

For a healthy pregnancy with no complications, the working target is roughly 150 minutes of moderate cardio a week — five sessions of 30 minutes, or 20 to 25 minutes on most days, whichever fits your week. Add strength work two or three times a week, 20 to 40 minutes a session.

Intensity is easiest to judge by talking: you should be able to hold a conversation in full sentences but not sing. On a 6-to-20 effort scale that lands around 12 to 14. Heart rate is a poor guide here, because pregnancy lifts your resting and working pulse by 10 to 20 beats a minute on its own. The old "stay under 140" rule was dropped long ago.

Two things need watching the whole way through: body temperature and fluid. Train somewhere cool, skip long efforts in the heat, and drink on a schedule rather than waiting to feel thirsty — how much water you actually need depends on your body mass and how much you sweat, and pregnancy quietly increases the losses.

First trimester (up to week 13)

Very little changes in how you train. Your bump is not in the way, your technique is unchanged — the problem is energy. Nausea and fatigue eat most of the motivation, and that is normal and temporary.

The fix is to cut volume rather than cut training. Three sets instead of four, four exercises instead of five, and two or three reps left in reserve on every set. If mornings are bad, move the session to the afternoon. A 20-minute walk on a write-off day still counts.

The one thing that comes off the list immediately is maximal effort: one-rep testing, personal bests, anything that requires bracing hard against a held breath. Everything else, squats and deadlifts at your usual working weights included, stays.

Second trimester (weeks 14 to 27)

For most women this is the best stretch. The nausea eases, energy comes back, and the bump is not yet limiting range of motion. Use it, but expect your centre of gravity to drift forward and the load on your lower back to climb with it.

The main lifts stay in the programme. In the squat a slightly wider stance and a little less depth usually feel better; in the deadlift, raising the bar onto blocks or pulling from the rack keeps you out of a deep hinge. Bring the loads down gradually, to something like 60 to 75 per cent of your old working weights, for sets of 8 to 15.

From around week 16 to 20, keep long spells lying flat on your back to a minimum. The evidence for real harm is thin, but in some women the pressure on the large vein behind the uterus causes dizziness and nausea — if that happens, prop the bench to an incline or roll onto your side. Swap crunches and floor sit-ups for anti-rotation and anti-extension work: suitcase carries, standing band presses, anything where the spine stays still and the trunk resists movement.

Third trimester (week 28 onwards)

Volume drops, frequency stays. Five short 20-minute sessions beat two long ones, because recovery is slower and sleep is broken.

Cardio moves to whatever does not jar the body: walking, stationary bike, cross-trainer, swimming. Water is particularly kind, since it takes the weight off the pelvis and lower back. Running is not banned if you ran before and it does not hurt, but most women switch to walking by around week 30 because of pelvic pressure.

For strength, choose the stable versions: goblet squats to a box, machine presses, supported rows, seated overhead presses, rack pulls. Unstable surfaces, jumping and anything with a real chance of losing your balance have no place here. If a lunge or single-leg stance produces a sharp pain in the groin or towards the pubic bone, drop those patterns and work both legs at once.

What comes out, no argument

This list does not depend on the trimester or on how well trained you are:

• Contact sports and anything with a genuine risk of falling — skiing, mountain biking, martial arts, riding.
• Scuba diving, at any stage.
• Hot yoga, saunas and long efforts in high heat.
• Breath-holding under strain, and maximal attempts in the gym.
• Lying prone the moment it becomes uncomfortable; there is nothing to gain by pushing through it.

Breathing, pelvic floor and the abdominal wall

The rule is short: breathe out through the hard part of the lift. Standing up out of a squat, pressing a bar overhead — exhale. That stops pressure building downwards onto a pelvic floor that is already carrying extra weight.

Train the pelvic floor daily and briefly: 3 sets of 10 holds of 3 to 5 seconds, plus 10 quick contractions. It works sitting at a desk or standing in a queue. This is one of the few parts of training worth increasing during pregnancy rather than trimming.

Separation of the abdominal muscles late in pregnancy happens to almost everyone and is not an injury. The signal that an exercise is too much is a ridge or dome running down the middle of the bump under effort — reduce the load or change the movement. Rebuilding that is postpartum work, whether your route is recovery after a caesarean or getting back to training while breastfeeding.

When to see a doctor

Clear your training plan with your obstetrician before you start if you have heart or lung disease, a low-lying placenta, a shortened cervix, pregnancy-related high blood pressure, a multiple pregnancy or a history of preterm birth. These are not calls to make on your own.

Stop training and get medical advice the same day if you notice:

• bleeding, or fluid leaking;
• regular painful contractions;
• chest pain, breathlessness before you have exerted yourself, or fainting;
• pain, redness or swelling in one calf;
• a severe headache, blurred vision, or sudden swelling of the face and hands.

The short version

• Aim for 150 minutes of moderate cardio a week plus strength work two or three times, at an effort where you can still speak in sentences.
• First trimester: same movements, volume down 20 to 30 per cent, no maximal attempts and no held-breath bracing.
• Second: keep the main lifts at 60 to 75 per cent of old loads, limit time flat on your back, retire the crunches.
• Third: shorter and more frequent sessions, stable exercise variations, low-impact cardio — walking, bike, water.
• Bleeding, leaking fluid, regular contractions, chest pain or a swollen calf mean stop and call a doctor that day.