Aim:  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.