The Pelvic Floor and Childbirth: What Really Happens and What Helps

By Dr Natalie Hutchins

Childbirth places one of the greatest physiological demands a woman’s body will ever experience on the pelvic floor. Yet despite how common postnatal pelvic floor symptoms are, many women remain unprepared for what happens during pregnancy and birth, and unaware that effective prevention and treatment exist.

Understanding how the pelvic floor functions, how it can be affected by childbirth, and what evidence-based care looks like can make a meaningful difference to recovery and long-term pelvic health.

What is the pelvic floor?

The pelvic floor is a group of muscles and connective tissues that form the base of the pelvis. These muscles:

• support the bladder, uterus and bowel

• contribute to urinary and bowel continence

• play a role in sexual function

• work as part of the core alongside the diaphragm and abdominal muscles

A healthy pelvic floor is not simply “strong”; it must also be coordinated, flexible and able to relax.

How does pregnancy affect the pelvic floor?

During pregnancy, the pelvic floor is exposed to increasing load from the growing uterus, changes in posture, and hormonal effects on connective tissue. Rising levels of the hormones relaxin and progesterone increase tissue compliance, which is necessary for birth but can also reduce support temporarily.

Many women experience pelvic floor symptoms during pregnancy, including urinary leakage, heaviness, or pelvic discomfort.

Evidence shows that pelvic floor muscle training during pregnancy reduces the risk of urinary incontinence during pregnancy and after birth, particularly in first-time mothers.¹

What happens to the pelvic floor during vaginal birth?

During vaginal birth, the pelvic floor must stretch significantly to allow the baby’s head to pass through the pelvic outlet. This stretch can exceed three times the muscle’s resting length, making childbirth one of the most extreme musculoskeletal events in human physiology.

Potential pelvic floor changes include:

• muscle overstretching or weakness

• nerve stretch or temporary denervation

• injury to connective tissue and fascia

• perineal tears or episiotomy

• levator ani muscle injury (levator avulsion)

Levator avulsion

Levator avulsion refers to partial or complete detachment of the levator ani muscle from its pubic bone attachment. It occurs almost exclusively during vaginal birth and is associated with an increased lifetime risk of pelvic organ prolapse.²

Importantly, avulsion cannot currently be surgically repaired, but early identification allows preventative strategies to reduce symptom progression.

Perineal tears: what matters clinically

Most perineal tears are first- or second-degree and heal well. Third- and fourth-degree tears (referred collectively as obstetric anal sphincter injuries, OASI as they involve the anal sphincter) are uncommon but clinically significant.

• Third-degree tears involve the anal sphincter

• Fourth-degree tears extend through the anal sphincter into the rectal mucosa

The most important thing is that they are identified and repaired correctly, and if this happens and is followed by specialist pelvic health care, many women recover well. Early pelvic floor physiotherapy and bowel management are essential to optimise outcomes.³

Can pelvic floor injury be reduced?

Evidence-based strategies shown to reduce pelvic floor injury risk include:

1. Perineal massage

A Cochrane review found that antenatal perineal massage from 34–36 weeks’ gestation reduces the risk of severe perineal trauma, particularly in first vaginal births.⁴

2. Birth position and sacral mobility

Positions that allow the sacrum to move freely (such as side-lying or upright positions) increase the pelvic outlet diameter and may reduce pelvic floor strain compared with supine positions.

3. Coordinated pushing

Teaching women how to relax and open the pelvic floor during the second stage of labour, rather than reflexively contracting it, is associated with a more efficient second stage and may reduce injury risk. Emerging evidence and clinical practice increasingly support antenatal pelvic floor assessment and coaching.⁵

Caesarean section: what does it protect against?

Caesarean delivery significantly reduces the risk of levator avulsion and pelvic organ prolapse compared with vaginal birth.⁶ However, it does not eliminate the risk of urinary incontinence later in life, particularly urgency and overactive bladder symptoms, which increase around menopause regardless of birth mode.

Decision-making around mode of birth should involve balanced, non-fear-based counselling, considering pelvic floor risk alongside obstetric, neonatal, and maternal factors.

Postnatal pelvic floor recovery: what is normal and what isn’t

In the early postnatal period, many women experience temporary pelvic floor symptoms that improve with time.

However:

• persistent urinary leakage

• ongoing pelvic heaviness or bulging

• difficulty emptying bladder or bowels

• pelvic pain or pain with sex

are not things women should simply accept.

Early pelvic health physiotherapy assessment allows clinicians to identify whether the pelvic floor is:

• weak

• overactive or tight

• poorly coordinated

• affected by scar tissue or nerve injury

Crucially, not all postnatal pelvic floor problems are due to weakness. In some women, particularly after difficult births, overactivity and guarding predominate, and indiscriminate strengthening (e.g. kegels or stimulation devices) can worsen symptoms.

The role of pelvic health physiotherapy

Pelvic health physiotherapy is a first-line, evidence-based intervention for postnatal pelvic floor dysfunction and includes:

• individualised pelvic floor rehabilitation

• coordination and relaxation training

• bowel and bladder management

• scar and tissue care

• guidance on safe return to exercise

• pessary fitting where appropriate

Multiple randomised controlled trials support its effectiveness in improving continence and prolapse symptoms and quality of life.⁸

Key take-home message

Pelvic floor changes during childbirth are common but long-term dysfunction is not inevitable. With informed preparation, early assessment, and evidence-based care, many pelvic floor problems can be prevented, improved, or managed effectively.

Further resources

• NHS – Pelvic floor exercises

  
  

• Royal College of Obstetricians and Gynaecologists – Pelvic floor health

  
  

• Pelvic Obstetric and Gynaecological Physiotherapy (POGP)

  
  

• National Childbirth Trust (NCT)

  
  

• International Urogynecological Association

  
  
  
  

References

1. Mørkved S, Bø K. Effect of pelvic floor muscle training during pregnancy and after childbirth on prevention and treatment of urinary incontinence. BMJ. 2003;327:1–5.

2. DeLancey JOL et al. Levator ani muscle injury, pelvic floor disorders, and childbirth. Am J Obstet Gynecol. 2007.

3. RCOG. The Management of Third- and Fourth-Degree Perineal Tears. Green-top Guideline No. 29.

4. Beckmann MM, Garrett AJ. Antenatal perineal massage for reducing perineal trauma. Cochrane Database Syst Rev. 2006.

5. Bø K, Sherburn M. Evaluation of pelvic floor muscle function after childbirth. Neurourol Urodyn. 2005.

6. Gyhagen M et al. Mode of delivery and pelvic floor disorders. BJOG. 2013.

7. MacLennan AH et al. Pelvic floor disorders and menopause. Climacteric. 2011.

8. Dumoulin C et al. Pelvic floor muscle training versus no treatment for urinary incontinence. Cochrane Database Syst Rev. 2018.