“…tocolysis, analgesia, abnormal vertex presentation, prolonged first stage, prolonged second stage, duration of labor, duration of pushing, pyrexia in labor, episiotomy, forceps, vacuum, birth weight, and head circumference. Among these, the following were significantly associated with anal sphincter laceration: episiotomy (OR, 3 Compared to "no analgesia", local, pudendal, or epidural analgesia all reduced the risk of anal sphincter laceration (Table 1). Interestingly, women who smoked and those with a BMI ≥ 30 kg/m 2 had a significantly lower risk of anal sphincter laceration (Fig.…”