A prospective observational study on the influence of the difficulty of forceps application and the avulsion of the levator ani muscle

Abstract

Background: To compare the rate of levator ani muscle (LAM) avulsion between normal deliveries (ND) and forceps deliveries (FD) and to determine whether the difficulty of forceps application in FD is related to the occurrence of LAM avulsion. Methods: This prospective observational study included 240 primiparous patients (125 ND and 115 FD). FD were classified according to the difficulty of forceps application. The application was considered difficult if the fetal head was in a transverse position or if it was midforceps (head engaged by the leading part was above +2 stations) with the fetal head in the occipito-posterior position; otherwise, the application was considered easy. Ultrasound evaluation was performed 6 months after delivery, and complete avulsion was diagnosed when there was abnormal insertion of the LAM in all three central slices. Results: There were statistically significant differences between the ND and FD groups in the presence of LAM avulsion (15.6% vs. 38.3%; p < 0.0005), with a crude Odds Ratio (OR) of 3.36 and an adjusted OR of 4.219. However, there were no statistically significant differences in the LAM avulsion rates between the easy and difficult application groups (34.2% vs. 45.2%; p: 0.244). Conclusions: FD have higher rates of LAM avulsion than ND, although the difficulty of forceps application does not have an influence on the rates of LAM avulsion.