Exercise During Pregnancy: What's Safe, What's Not, and What Your Body Actually Needs

The fear problem

Pregnant women receive more conflicting exercise advice than any other population. One source says strength training is fine through the third trimester. Another says avoid anything that raises your heart rate above 140 bpm (a guideline the American College of Obstetricians and Gynecologists abandoned in 1994 — yet it persists in gym culture three decades later). A third says just walk and do yoga.

The result is that most pregnant women either stop exercising entirely (out of fear) or continue their exact pre-pregnancy program (out of defiance). Neither approach is optimal. The body changes during pregnancy — structurally, hormonally, and biomechanically — and training should adapt to those changes. Not stop. Adapt.

This guide covers what actually changes, when, and how training should respond. No fear-based restrictions. No generic “listen to your body” non-advice. Specific modifications based on specific structural changes, supported by the current evidence.

What the research actually says about exercise during pregnancy

The evidence base for prenatal exercise is large and consistent. ACOG, the Canadian Society for Exercise Physiology (CSEP), and the Royal College of Obstetricians and Gynaecologists (RCOG) all recommend 150 minutes per week of moderate-intensity exercise for uncomplicated pregnancies. This is not a tentative suggestion — it is a strong, evidence-based recommendation.

The benefits are measurable:

• Gestational diabetes risk: 25-30% reduction with regular exercise (Davenport et al., 2018, systematic review of 103 studies)
• Preeclampsia risk: 40% reduction with regular moderate exercise (Aune et al., 2014)
• Excessive gestational weight gain: 32% reduction (Muktabhant et al., 2015, Cochrane review)
• Cesarean delivery: 15% reduction in scheduled cesareans (Di Mascio et al., 2016)
• Postpartum depression: Significant reduction in incidence (Davenport et al., 2018)
• Labor duration: Active labor 50-90 minutes shorter in women who exercise regularly (Perales et al., 2016)

The risks of exercise during uncomplicated pregnancy — meaning no placenta previa, no cervical insufficiency, no preeclampsia, no preterm labor risk — are minimal. The risk of not exercising is substantially higher.

Structural changes by trimester

Pregnancy produces specific, predictable structural changes. Understanding these changes is the foundation for smart programming modifications.

First trimester (weeks 1-12)

Hormonal changes: Relaxin levels begin to rise. Relaxin increases ligamentous laxity throughout the body, not just the pelvis. Joint stability decreases, particularly at the sacroiliac joint, pubic symphysis, and smaller joints (wrists, ankles).

Structural implications: Most structural changes are not yet visible. The uterus remains within the pelvis. Center of gravity has not shifted. The primary concern is relaxin-mediated joint laxity, which means:

• Avoid maximal or near-maximal loading (> 85% 1RM). The ligamentous system is less stable, and heavy loading increases injury risk at the SI joint and lumbar spine.
• Reduce ballistic movements (box jumps, plyometrics) — landing forces are distributed across joints that are now less stable.
• Maintain current training intensity but cap it at RPE 7-8 rather than pushing to failure.

What stays the same: Exercise selection can remain largely unchanged. Squats, deadlifts, pressing, pulling, rowing, carrying — all appropriate at moderate loads.

Second trimester (weeks 13-27)

Structural changes: The uterus rises above the pelvis. The center of gravity shifts anteriorly. The anterior pelvic tilt increases. Lumbar lordosis increases to compensate. Thoracic kyphosis often increases as a downstream compensation. Abdominal wall stretching begins (diastasis recti typically starts becoming measurable around week 16-20).

This is where modifications matter most:

Supine position: After week 16-20, avoid prolonged supine exercise (more than 2-3 minutes). The uterus can compress the inferior vena cava, reducing venous return and causing dizziness or hypotension. This does not mean supine exercise is banned — short sets of supine pressing or bridging are fine. But extended supine holds (long stretching, floor-based core work) should be replaced with side-lying or inclined alternatives.

Anterior loading: As the anterior pelvic tilt increases, exercises that increase lumbar extension load should be modified:

• Back squat → goblet squat or front squat (shifts load anterior, reduces lumbar extension demand)
• Conventional deadlift → sumo deadlift or trap bar deadlift (wider stance accommodates belly, reduces lumbar moment arm)
• Standing overhead press → seated or incline pressing (reduces demand on lumbar stabilization)

Core training: Traditional crunches, sit-ups, and planks should be replaced by:

• Pallof press (anti-rotation)
• Side plank (anti-lateral flexion)
• Bird-dog (anti-extension with contralateral demand)
• Diaphragmatic breathing with pelvic floor engagement

The goal shifts from generating force through the anterior core to maintaining tension and position. The abdominal wall is stretching to accommodate the growing uterus — loading it concentrically (shortening) creates pressure on the linea alba and increases diastasis risk.

Balance: Center of gravity shifts create balance challenges. Single-leg work should include external support (hand on a wall, TRX strap). Not because single-leg work is dangerous — because falling is dangerous.

Third trimester (weeks 28-40)

Structural changes: Maximum anterior shift. Significant lordotic increase. Pelvic floor load is at its highest. Relaxin levels peak. Joint laxity is maximum. Breathing mechanics are compromised — the diaphragm cannot descend fully because the uterus occupies much of the abdominal cavity.

Programming priorities shift to maintenance and preparation:

• Intensity: Reduce to RPE 6-7. The cardiovascular system is working harder at baseline (cardiac output increases 30-50% during pregnancy). Subjective effort scales are less reliable because baseline effort has increased.
• Volume: Reduce total training volume by 20-30% from second trimester levels. Recovery is slower. Sleep is compromised. Training is medicine, not punishment.
• Exercise selection: Focus on movements that reinforce the positions needed for labor and postpartum recovery:
  • Deep squats (with support if needed) — practice the position the body will use during labor
  • Hip hinge patterns — maintain posterior chain strength for carrying an infant
  • Pulling patterns — upper back strength for breastfeeding posture
  • Pelvic floor work — both engagement (Kegels, but with proper coordination) and release (equally important and often overlooked)

What to stop: High-impact activities (running, jumping) if there is pelvic floor symptoms (leaking, heaviness, pressure). Contact sports. Activities with fall risk. Heavy Valsalva maneuvers.

The pelvic floor: the most neglected structure

The pelvic floor is the structure that bears the most direct load during pregnancy and the structure that receives the least attention in most training programs. It is not a single muscle — it is a group of muscles that form a sling at the base of the pelvis, supporting the bladder, uterus, and rectum.

During pregnancy, the pelvic floor bears progressively increasing load as the uterus grows. A full-term uterus weighs 4-5 kg (including baby, amniotic fluid, and placenta). That load sits directly on the pelvic floor for months.

Pelvic floor training during pregnancy

The standard advice is “do Kegels.” This is incomplete. Pelvic floor training during pregnancy requires two components:

1. Contraction (engagement)

Standard Kegel — contract the pelvic floor as if stopping urination, hold for 5-10 seconds, release for 10 seconds, repeat 10 times. Three sets per day. This maintains pelvic floor strength and endurance under increasing load.

2. Relaxation (release)

Equally important and rarely taught. The pelvic floor must be able to relax and lengthen during labor. A hypertonic (overly tight) pelvic floor is associated with longer pushing stages and higher rates of perineal tearing.

Release practice: Deep diaphragmatic breath while consciously relaxing the pelvic floor on the exhale. The sensation is the opposite of a Kegel — instead of lifting and tightening, allow the pelvic floor to soften and expand downward. Practice in a deep squat position or child’s pose.

When to see a pelvic floor physiotherapist

Every pregnant woman benefits from at least one pelvic floor physiotherapy assessment. Specifically, seek assessment if:

• Any urinary leaking during exercise, coughing, or sneezing
• Pelvic heaviness or pressure, especially after exercise or at the end of the day
• Pain during intercourse
• Difficulty activating or releasing the pelvic floor voluntarily
• History of pelvic floor dysfunction, prior birth injury, or chronic constipation

Absolute contraindications: when to stop exercising

These are non-negotiable. If any of the following are present, exercise stops until cleared by an OB-GYN:

• Vaginal bleeding
• Regular painful contractions before 37 weeks
• Amniotic fluid leakage
• Persistent dizziness or chest pain during exercise
• Calf pain or swelling (rule out DVT)
• Diagnosed placenta previa after 28 weeks
• Cervical insufficiency or cerclage
• Preeclampsia or pregnancy-induced hypertension

These are not common. Most pregnancies are uncomplicated, and exercise is not just safe but strongly recommended. But screening for these conditions should happen at every prenatal visit, and any new symptoms should be reported immediately.

What about abs? Diastasis recti explained

Diastasis recti abdominis (DRA) — separation of the rectus abdominis muscles along the linea alba — occurs in virtually every pregnancy. Studies show 100% prevalence at 35 weeks and 30-40% prevalence at 6 months postpartum.

The separation is normal. The linea alba stretches to accommodate the growing uterus. The question is not whether it happens but how wide it gets and whether it recovers postpartum.

What influences DRA severity:

• Genetics: Connective tissue quality varies between individuals
• Previous pregnancies: Each pregnancy tends to increase separation
• Exercise selection during pregnancy: Heavy anterior core loading (crunches, planks, sit-ups) can increase separation
• Abdominal pressure management: Breath-holding under load (Valsalva) increases intra-abdominal pressure and loads the linea alba

What helps during pregnancy:

• Avoid exercises that create a visible “coning” or “doming” of the abdominal midline
• Practice exhale on exertion (breathe out during the hardest part of the lift) rather than holding breath
• Favor anti-extension and anti-rotation core work over concentric core work
• Maintain posterior chain and lateral core strength to reduce anterior demand

Postpartum recovery:

DRA recovery is a postpartum topic, but the foundation is laid during pregnancy. Women who maintain appropriate core training during pregnancy (modified, not eliminated) tend to recover faster than those who either train aggressively through the core or stop all core work entirely.

Sample week: second trimester training

This is a template for a previously active woman in weeks 16-24 of an uncomplicated pregnancy. Adjust loads and volume based on individual assessment and how the body responds day to day.

Day 1 — Lower body

• Goblet squat: 3 x 10 @ RPE 7
• Romanian deadlift (DB): 3 x 10 @ RPE 7
• Lateral band walk: 3 x 12 each direction
• Side-lying clamshell: 3 x 15 each side
• Pelvic floor: 10 contract-release cycles

Day 2 — Upper body

• Incline DB press: 3 x 10 @ RPE 7
• Seated cable row: 3 x 12 @ RPE 7
• Half-kneeling single-arm press: 3 x 10 each side
• Band pull-apart: 3 x 15
• Pallof press: 3 x 8 each side

Day 3 — Full body / movement

• 20-minute walk
• Sumo deadlift: 3 x 8 @ RPE 6
• Supported single-leg RDL: 3 x 8 each side
• Bird-dog: 3 x 8 each side (slow, 3-second holds)
• Deep squat hold (supported): 3 x 30 seconds
• Pelvic floor: 10 contract-release + 5 release-emphasis cycles

Day 4 — Active recovery

• 30-minute walk or swim
• Gentle stretching focusing on thoracic extension and hip opening
• Diaphragmatic breathing: 5 minutes

The postpartum bridge

What you do during pregnancy sets up postpartum recovery. Women who maintain strength, ROM, and pelvic floor awareness during pregnancy return to full training faster and with fewer complications than those who stop training entirely.

The structural assessment framework applies equally to postpartum recovery. Pregnancy creates measurable structural changes — increased anterior pelvic tilt, altered thoracic position, pelvic floor changes. A postpartum assessment provides the baseline for structured recovery rather than guessing at when it is “safe” to return to running, lifting, or sport.

Pregnancy is not an injury. It is a structural event that changes the body in predictable, measurable ways. Train for it. Adapt through it. Recover from it with data, not guesswork.

---

Pregnant and want to train smart? Find an AKMI-certified coach experienced with prenatal and postpartum programming, or learn about our assessment method.