Exploring the influence of perineal biometrics and stiffness measured by elastography during pregnancy on perineal...

This study aimed to describe the biometrics and elasticity of the perineal body and the anal sphincter in the ninth month of pregnancy and explore their association with the risk of perineal tears during childbirth.

In this prospective observational study, pregnant women at 36-40 weeks of gestation were included. Using transperineal 2D-mode ultrasound and shear wave elastography (SWE), we measured the biometrics and stiffness of the perineal body (PB), external anal sphincter (EAS), internal anal sphincter (IAS), and anal mucosa (AM) at rest and during Valsalva maneuvers.

Of the 16 women, five (31.2 %) were nulliparous and 10 (62.5 %) underwent a perineal tear. All were first degree perineal tears. Women with perineal tear had statistically a higher perineal body area at rest (0.9 ± 0.1 cm² versus 0.7 ± 0.1 cm², p = 0.03), a thicker EAS at 9 o'clock at rest (0.6 ± 0.2 cm vs 0.4 ± 0.1 cm, p = 0.03), a smaller anteroposterior diameter (1.7 ± 0.2 cm vs 2 ± 0.2 cm, p = 0.047), a smaller lateral diameter (1.4 ± 0.2 cm vs 1.6 ± 0.1 cm, p = 0.05) and a thinner IAS in average at rest (0.2 ± 0.0 cm vs 0.3 ± 0.0 cm, p = 0.007) and at 12 o'clock at rest (0.2 ± 0.1 cm vs 0.3 ± 0.0 cm, p = 0.002). The PB, EAS, IAS and AM elastic modulus in the ninth month of pregnancy tended to be higher in women with a perineal tear.

Assessing perineal and anal sphincter biometrics and stiffness via ultrasound and SWE is feasible and may indicate a risk of perineal tears.

The study was registered on (NCT05556304).