Prenatal · 11 min read
Safe exercises during pregnancy: a trimester-by-trimester guide
First, second, and third trimester each need different things. Generic prenatal advice flattens all three into one. Here's how I actually program for each — and which lifts get modified when.
By Lexi Krieger · NASM-CPT, Pre/Postnatal Performance Specialist · April 22, 2026
Pregnancy isn't 40 weeks of the same body. First trimester is exhaustion and nausea with a body that looks the same. Second trimester is the magic window — energy returns, the bump is visible, training is the easiest of the three. Third trimester is everything-changes-weekly territory.
Generic prenatal advice — "just walk and listen to your body" — flattens all three into one. Here's how I actually program for each.
First trimester (weeks 1-13)
What's happening in your body
Massive hormonal shifts. Progesterone surges, relaxin starts loosening joints, blood volume increases dramatically. Most women feel exhausted and nauseous, with peak symptoms around weeks 6-9.
What to do
- Keep training at roughly your pre-pregnancy intensity if you feel okay. Don't start something dramatically new.
- Strength training: maintain weights, drop volume slightly if needed. RPE 6-7 (out of 10) is plenty.
- Cardio: keep what you were doing. Listen to your heart rate and breath — "talk test" still applies.
- Sleep more, eat more, hydrate more.
What to avoid
- Hot yoga, sauna, or anything that overheats core body temperature.
- Brand-new high-intensity programs (CrossFit, F45 first-timer) — your body is already adapting to a lot.
- Caffeine over ~200mg/day per most OB guidelines.
Second trimester (weeks 14-27)
What's happening in your body
Energy returns. Nausea usually fades. The bump becomes visible around weeks 16-20. Center of gravity shifts forward, which subtly changes your squat, deadlift, and overhead positions.
What to do
- This is your peak training trimester. Strength work, conditioning, mobility — all of it.
- Pelvic floor and core training every session: diaphragmatic breathing, transverse abdominis engagement, glute activation.
- Continue lifting weights with full ROM. Squats, deadlifts, presses, rows — all on the menu with modifications.
- Add specific labor-prep work: deep squats, hip mobility, controlled breath under load.
What to modify (starting around week 20)
- Stop lying flat on your back for any sustained work — supine positions can compress the vena cava and reduce blood flow. Use an incline (bench at 30-45°) or a side-lying position instead.
- Drop weight on traditional sit-ups and crunches — and avoid them entirely once you have a visible bump. Train the deep core instead.
- Watch for coning on any front-loaded movement (planks, push-ups, hanging). Coning = your linea alba is being overloaded. Regress the movement.
- Avoid hot yoga, saunas, and any prolonged overheating.
Third trimester (weeks 28-40+)
What's happening in your body
Center of gravity is fully shifted. Joints are looser (relaxin is doing its job). Belly is large enough to interfere with certain positions. Energy can dip again toward the end. Many women experience back, hip, or pelvic pain.
What to do
- Continue training, but reduce intensity and adjust frequency as needed.
- Strength work: drop loads, slow the tempo, increase rest. RPE 5-7.
- Increase mobility work: hips, ankles, thoracic spine, pelvic floor releases.
- Birth-prep work: deep squat holds, diaphragmatic breathing, pelvic floor down-training (learning to release the floor, not just engage it).
- Walk. Lots. Walking is genuinely the unsung hero of late pregnancy.
What to modify or avoid
- Most barbell back squats and deadlifts become impractical due to the bump. Switch to goblet squats, dumbbell RDLs, kettlebell deadlifts, or trap bar.
- Long planks and hanging movements — usually out by third trimester.
- Box jumps, high-impact plyometrics, and anything with high fall risk — your balance is genuinely different.
- Anything that triggers pelvic pain or instability. Pubic symphysis dysfunction is real — if a lift makes it worse, drop it.
Universal red flags — stop and call your OB
- Vaginal bleeding or fluid leakage
- Persistent dizziness, faintness, or visual changes
- Calf pain or swelling (DVT signs)
- Reduced fetal movement after week 28
- Painful uterine contractions
- Chest pain or shortness of breath disproportionate to effort
How to work with me during pregnancy
I program prenatal training in three buckets: maintain (1st trimester), build (2nd trimester), prep (3rd trimester). Group classes have prenatal modifications baked in. 1-on-1 sessions are fully customized to your week and your OB's guidance. See prenatal training, or DM me with questions about where you are.
