Racial/ethnic variations in perineal length and association with perineal lacerations: A prospective cohort study

Objective: To examine the association between race/ethnicity, perineal length and the risk of perineal laceration. Methods: This is a prospective cohort study of a diverse group of women with singleton gestations in the third trimester of pregnancy. Perineal length was measured and mean values calculated for several racial/ethnic groups. Chi-squared analyses were used to examine rates of severe perineal laceration (third or fourth degree laceration) by race/ethnicity among women considered to have a short perineal length. Further, subgroup analyses were performed comparing nulliparas to multiparas. Results: Among 344 study participants, there was no statistically significant difference in mean perineal length by race/ethnicity (White 4.0±1.1cm, African-American 3.7±1.0cm, Latina 4.1±1.1cm, Asian 3.8±1.0cm, and other/unknown 4.0±0.9cm). Considering parity, more multiparous Asian and African-American women had a short perineal length (20.7 and 23.5%, respectively, p=0.05). Finally, the rate of severe perineal lacerations in our cohort was 2.6% overall, but was 8.2% among Asian women (p=0.04). Conclusions: We did not find a relationship between short perineal length and risk of severe perineal laceration with vaginal delivery, or a difference in mean perineal length by maternal race/ethnicity. However, we did find that women of different racial/ethnic groups have varying rates of severe perineal laceration, with Asian women comprising the highest proportion.