title: Using anovaginal distance at the beginning of labor to predict the likelihood of instrumental delivery.
abstract: OBJECTIVE
  To investigate whether anovaginal distance in parturients has an impact on the instrumental delivery rate.
  
  
  METHODS
  In this study with prospective data collection and a convenience sample, 400 parturients planning for vaginal delivery at term with a singleton fetus in vertex presentation were enrolled. Anovaginal distance was measured in the lithotomy position during the latent phase of labor or early first stage. This distance is thought to reflect the angle of inclination of the birth canal axis.
  
  
  RESULTS
  At the cutoff point of 25 mm for anovaginal distance, the odds ratio for instrumental delivery was 2.5 (95% CI 1.48-6.6, p<0.05). A final model of instrumental delivery, controlling for various confounding variables, correctly predicted 91.38% of the instrumental deliveries (p<0.0001). The variables anovaginal distance >25 mm (OR 2.9, 95% CI 1.2-6.7, p=0.01), parity (OR 0.54, 95% CI 0.29-0.99, p=0.046) and duration of second stage of labor (OR 1.01, 95% CI 1.004-1.01, p=0.001) significantly contributed to the prediction of instrumental delivery after controlling for the other parameters.
  
  
  CONCLUSIONS
  Women with an anovaginal distance of >25 mm at the beginning of labor was 2.5 more likely to undergo instrumental delivery than were women with an anovaginal distance of <25 mm.
authors.affiliation: Department of Obstetrics and Gynecology, Edith Wolfson Medical Center, Holon, Israel. drslurie@hotmail.com
authors.forename: Samuel
authors.initials: S
authors.lastname: Lurie
authors.forename: Mona
authors.initials: M
authors.lastname: Boaz
authors.forename: Oscar
authors.initials: O
authors.lastname: Sadan
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000033:anatomy & histology*; D001837:Body Weights and Measures; D005113:Extraction, Obstetrical; D005260:Female; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D014621:Vagina / Q000033:anatomy & histology*