Can pelvic floor muscles be too tight to give birth?

Women should be encouraged to do regular PFM exercises during pregnancy to prevent urinary incontinence1.  Concern has been expressed that a tight, strong pelvic floor may obstruct or delay labour and result in instrumental or surgical birth, cause muscle and connective tissue detachment, perineal trauma and damage to nerves.

A study By Kari Bo et  al2of women giving birth at a university hospital looked at vaginal resting pressure (VGP), PFM strength and endurance in 300 nulliparous pregnant women assessed at mean gestational week 20.8 using a high precision pressure transducer connected to a vaginal balloon. Women with a significantly higher vaginal resting pressure had a prolonged second stage (defined as more than two hours).

The authors results showed ‘that mid pregnancy VRP may be associated with prolonged second stage of labour. However neither VRP or PFM strength nor endurance was associated with operative delivery or perineal tears, and the clinical relevance of such a small risk can be discussed. PFM strength and endurance did not influence the outcome of the delivery. Strong PFMs are not disadvantageous for vaginal delivery.

This study highlights that PFM strength and endurance are not associated with surgical birth or perineal tears. The authors showed that higher mid pregnancy vaginal resting pressure is associated with a prolonged second stage of labour. Higher vaginal resting pressure is associated with over activity in PFM.

  1. Boyle R, Hay-Smith E, Cody J, Morkved S (2012)Pelvic floor muscle training for prevention and treatment of urinary incontinence and faecal  incontinence in antenatal and postnatal women. Cochrane Database Syst Rev 10:CD007471Doi:10.1002/14651858.CD007471.pub2
  2. Bo et al Too tight to give birth? Assessment of pelvic floor muscle function in 277 nulliparous pregnant women. Int Urogynecol J. (2013) 24:2065-2070