title: Rate of postdates induction using first-trimester ultrasound to determine estimated due date: Wellington Regional Hospital audit.
abstract: OBJECTIVE
  The aim of this audit was to examine the effect of using first-trimester (<14 weeks) ultrasound scan to determine EDD (US EDD) on the rate of induction for postdates pregnancies at Wellington Regional Hospital.
  
  
  METHODS
  Women with singleton live pregnancies who had postdates (≥41 weeks) induction at Wellington Hospital during January 2009 to November 2009 were identified using a computerised database [Perinatal Information Management System (PIMS)]. The first-trimester ultrasound images and reports for these women were retrieved and reviewed by a specialist in obstetric ultrasound. Only ultrasound studies that had technically satisfactory images at <14 weeks were included.
  
  
  RESULTS
  A total of 329 women with a singleton live pregnancy were induced for postdates during the study period. Of these women, 50 (15.2%) were not ≥41 weeks on PIMS EDD and therefore on the best available evidence should not have been induced for being postdates. Of the remaining 279 women, 158 had first-trimester scans available for review. Forty-three of 158 (27%) were <41 weeks when US EDD was used.
  
  
  CONCLUSIONS
  The rate of postdates inductions at Wellington NRH could be decreased by 38% if induction was limited to women over 41-week gestation and by using US EDD as opposed to last menstrual period EDD. The use of early gestational scans (<14 weeks) to estimate EDD lowers the rate of postdates induction. This is very similar to the observed findings in literature.
authors.affiliation: Obstetrics and Gynaecology, Women's Health Service, Wellington Public Hospital, Wellington South, New Zealand.
authors.forename: May
authors.initials: M
authors.lastname: Tun
authors.forename: Jeremy
authors.initials: J
authors.lastname: Tuohy
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005865:Gestational Age; D006801:Humans; D007751:Labor, Induced; D008485:Medical Audit; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011273:Pregnancy, Prolonged / Q000000981:diagnostic imaging*; D016216:Ultrasonography, Prenatal; D055815:Young Adult