• genital tract trauma;
  • nulliparity;
  • obesity;
  • gestational weight gain


The purpose of this study was to explore the impact of body mass index (BMI) or pregnancy weight gain on the presence, site, and severity of genital tract trauma at childbirth in nulliparous women.


The present study is a subanalysis of a prospective cohort of healthy nulliparous women recruited during pregnancy and followed through birth. Weight gain during pregnancy and prepregnancy BMI were recorded. At birth, women underwent detailed mapping of genital tract trauma. For analyses, women were dichotomized into obese (BMI ≥ 30) versus nonobese (BMI < 30) at baseline as well as into those who gained weight as recommended by the Institute of Medicine (IOM) and those who gained more than the recommended amount to determine the impact of obesity or excessive weight gain on rates of genital tract trauma.


Data from 445 women were available for analysis. Presence and severity of genital tract trauma did not vary between obese and nonobese women (51% vs 53%, P = .64). Likewise, women who had more than the IOM-recommended weight gain did not have a higher incidence of perineal lacerations (52% versus 53% with perineal lacerations, = .69). Obese women were more likely to gain in excess of the IOM guidelines during pregnancy (75% vs 50% excessive weight gain in obese vs nonobese women, respectively; < .001).


A woman's BMI or excessive weight gain in pregnancy did not influence her risk of genital tract trauma at birth.