Ultrasound imaging of the pelvic floor: changes in anatomy during and after first pregnancy

Abstract

Objectives To describe changes in the absolute values of levator hiatal dimensions and in the contractility and distensibility of hiatal dimensions during pelvic floor contraction and Valsalva maneuver using three/four‐dimensional (3D/4D) transperineal ultrasound in women during and after their first pregnancy. Methods 280 nulliparous pregnant women underwent ultrasound examination at 12 weeks’ gestation, 36 weeks’ gestation and six months postpartum. Hiatal dimensions were measured at rest, on pelvic floor contraction and on Valsalva maneuver. The contractility and distensibility were determined by the difference between hiatal dimensions at rest and on contraction or Valsalva. Data at 36 weeks’ gestation and six months postpartum were compared with 12 weeks’ gestation. Results At 36 weeks’ gestation, the absolute values of hiatal dimensions and the contractility and distensibility of hiatal dimensions were significantly increased compared with 12 weeks’ gestation. Women who delivered vaginally showed a persistent significant increase in hiatal dimensions on Valsalva, while women who delivered by prelabor or first stage Cesarean section showed no significant changes in hiatal dimensions on Valsalva. Both after vaginal and Cesarean childbirth, there was a persistent increase in the distensibility of hiatal dimensions during Valsalva compared with early pregnancy. Conclusions During first pregnancy, the absolute values of levator hiatal dimensions and the contractility and distensibility of hiatal dimensions increase. Independent of delivery mode, increased distensibility of hiatal dimensions during Valsalva persists after childbirth. This increased pelvic floor distensibility may play a role in the development of pelvic floor dysfunction in later life.