Too tight to give birth? Assessment of pelvic floor muscle function in 277 nulliparous pregnant women

Abstract

Introduction and hypothesis: Theoretically, tight or strong pelvic floor muscles may impair the progress of labor and lead to instrumental deliveries. We aimed to investigate whether vaginal resting pressure, pelvic floor muscle strength or endurance at mid-pregnancy affect delivery outcome. Methods: this was a prospective cohort study of women giving birth at a university hospital. Vaginal resting pressure, pelvic floor muscle strength and endurance in 300 nulliparous pregnant women were assessed at mean gestational week 20.8 (±1.4) using a high precision pressure transducer connected to a vaginal balloon. Delivery outcome measures (acute cesarean section, prolonged second stage of labor (> 2 hours), instrumental vaginal delivery (vacuum and forceps), episiotomy and 3 rd and 4 th degree perineal tear) were retrieved from the hospital's electronic birth records. Results: Twenty-three women were lost to follow-up, mostly because they gave birth at another hospital. Women with prolonged second stage had significantly higher resting pressure than women with second stage less than 2 hours; mean difference 4.4 cm H 2 O (95% CI: 1.2-7.6), p<0.01, aOR: 1.049 (95% CI: 1.011-1.089, p=0.012). Vaginal resting pressure did not affect other delivery outcomes. Pelvic floor muscle strength and endurance similarly were not associated with any delivery outcomes. Conclusions: While mid-pregnancy vaginal resting pressure is associated with prolonged second stage of labor, neither vaginal resting pressure nor pelvic floor muscle strength or endurance are associated with operative delivery or perineal tears. Strong pelvic floor muscles are not disadvantageous for vaginal delivery.

Does episiotomy influence vaginal resting pressure, pelvic floor muscle strength and endurance, and prevalence of urinary incontinence 6 weeks postpartum?

“…One important factor that may influence PFM variables after childbirth is PFM function before childbirth. However, in a previously published study from the same cohort, we reported that VRP, PFM strength and endurance measured at gestational week 21 were not significantly different in women with or without episiotomy, or women with or without instrumental vaginal delivery . Hence, PFM function before childbirth cannot be considered a confounding factor in relation to VRP, PFM strength and endurance at 6 weeks postpartum in this cohort of primiparous women.…”

Exercise and pregnancy in recreational and elite athletes: 2016 evidence summary from the IOC expert group meeting, Lausanne. Part 2—the effect of exercise on the fetus, labour and birth

“…Risk factors for a prolonged second stage include fetal head position that is not occiput anterior, fetal size, epidural anaesthesia and parity 81 82. A systematic review of five studies, including 879 patients,83 concluded that data are insufficient to draw conclusions about the effect of body position during pushing in women with epidural anaesthesia on the duration of second stage or on the need for instrumented deliveries 84…”

Effects of antenatal pelvic floor preparation techniques on the perineal integrity: a randomized controlled trial protocol

“…Therefore, well conducted stretching techniques for short periods and a controlled muscle strength previously trained by specific exercises, with more muscle awareness, coordination and flexibility, contribute to a lower likelihood of perineal injury. [11][12][13][14][15][16][17][18]29 Few studies have evaluated the effects of Epi-No® in perineal outcomes and on the role of PFM, and the existing results are still inconsistent due to lack of studies with methodological rigor and also directed to the Brazilian population.…”

“…16,30 In addition, uncontrolled activation of MAP, with or without abdominal muscles training, can increase the PFM tension, resulting in a resistance of the delivery canal, representing an obstacle to the passage of the baby. 28,30 However, other studies claim that antenatal TMAP improves flexibility, strength and motor control, facilitating the passage of the baby during the second delivery stage, reducing the need for instrumental delivery and the risk of injury.…”

“…Few studies used PFMT aiming birth outcomes. [11][12][13][14][15][16][17][18] Du et al in a systematic review with meta-analysis found that PFMT during pregnancy was effective in reducing the time of the first and second stages of labor in primiparae. 10 In contrast, it was not found significant association between antenatal PFMT with the reduction in episiotomy rates, need for instrumental vaginal delivery and a reduction at the risk of perineal laceration.…”