Important: This article summarizes published research and clinical guidelines. It is not medical advice. Every pregnancy is different. Medical clearance from your OB-GYN or midwife is non-negotiable before continuing or starting a running program during pregnancy, and before returning to running postpartum. If anything in this article conflicts with guidance from your healthcare provider, follow your provider’s advice — they know your situation, we don’t.

Running During Pregnancy

The American College of Obstetricians and Gynecologists (ACOG) recommends at least 150 minutes of moderate-intensity aerobic activity per week during uncomplicated pregnancies. Running falls within this guidance for women who were running before pregnancy.

By Trimester

First trimester: Fatigue and nausea may reduce training capacity even though nothing has visibly changed. Many women can continue their pre-pregnancy running with minor adjustments. Listen to your body — if you need to cut back, cut back. There is no evidence that moderate running increases miscarriage risk in uncomplicated pregnancies.

Second trimester: Many women feel a return of energy and can maintain moderate running. This is often the most comfortable trimester for running. As your center of gravity shifts, balance may change — be aware on uneven terrain.

Third trimester: Biomechanical changes — center of gravity shift, joint laxity from relaxin, pelvic floor loading, and the sheer physical presence of a growing baby — often make running uncomfortable or impractical. This is normal and expected. Switching to walking, swimming, or cycling is not giving up. It’s adapting to your body’s current state.

Guidelines During Pregnancy

  • Use RPE rather than pace or heart rate. Your cardiovascular system is working harder at baseline during pregnancy (blood volume increases by 30-50%). Pace and heart rate targets from before pregnancy no longer apply.
  • Avoid overheating. Skip hot weather runs, stay hydrated, and don’t exercise in extreme heat. Maternal hyperthermia is a real concern, especially in the first trimester.
  • Stop and contact your provider if you experience vaginal bleeding, dizziness, chest pain, calf swelling, regular contractions, or amniotic fluid leakage.
  • Pelvic floor awareness. The pelvic floor is under increasing load as pregnancy progresses. If you experience heaviness, pressure, or leaking during runs, that’s a signal to modify — not to push through.

Returning to Running Postpartum

A 2020 consensus guideline from Donnelly, Goom, and colleagues — published in the British Journal of Sports Medicine — recommends a minimum of 12 weeks postpartum before returning to running. This applies to both vaginal and cesarean deliveries.

Why the Wait

Pregnancy and delivery place significant load on the pelvic floor muscles, which support your organs and manage intra-abdominal pressure during running. Running is a high-impact activity that generates ground reaction forces of 2-3 times body weight per stride. Returning before these tissues have recovered increases the risk of pelvic organ prolapse, stress urinary incontinence, and pain.

The 12-week guideline isn’t arbitrary conservatism. It’s based on tissue healing timelines: the uterus takes 6-8 weeks to return to pre-pregnancy size, and pelvic floor and abdominal wall tissue repair continues well beyond that.

Before You Run Again

Functional milestones matter more than a calendar date:

  • Can you walk for 30 minutes without pain, heaviness, or leaking?
  • Can you do single-leg balance, single-leg squats, and single-leg calf raises without symptoms?
  • Can you hop on one leg without leaking or discomfort?

A pelvic floor physiotherapist can assess readiness in ways that a general practitioner often cannot. If you have access to one, a pre-return assessment is highly recommended.

The Return Protocol

When you do return, start with run/walk intervals and progress conservatively:

  • Weeks 1-2: Run 1 min / Walk 2 min, 3 times per week
  • Weeks 3-4: Gradually increase run intervals, decrease walk intervals
  • Monitor for symptoms at each stage: leaking, heaviness, pelvic pain, or low back pain are signals to pull back, not push through

This is exactly the kind of conservative, gradual progression that Pacewright’s algorithm is designed for. The principles are the same as any return from a break — the ACWR guardrails protect you from doing too much too soon.

A Note on Stress Urinary Incontinence

Leaking during running is reported by approximately 30-45% of female runners who have given birth. It is a treatable musculoskeletal issue, not a permanent condition and not a reason to stop running.

Pelvic floor physiotherapy — working with a specialist who can assess whether the issue is weakness, tension, or coordination — is the most effective treatment. Generic “just do Kegels” advice often misses the mark because the problem isn’t always simple weakness.

If this is happening to you, you’re not alone, and you don’t have to accept it. A pelvic floor specialist is the right first step.