Dating biometry during the first trimester: accuracy of an every-day practice

Abstract Objective : The goal of this study was to determine the accuracy of an every-day practice for assessing gestational age by ultrasound measurement of the greatest embryonic length (GEL). Design : This retrospective study used measurements taken during the first trimester. Subjects : We considered all births in this hospital between 1 January 1992 and 31 December 1994 from pregnancies that began by an in-vitro fertilization procedure (IVF). We examined 143 consecutive files, containing 257 measurements made by 72 different operators. Methods : The precision of seven embryo growth curves was compared. We calculated for each curve its ability to predict (95% prediction interval) the date the pregnancy began, using these dated pregnancies. Result : For GEL measurements between 3 and 80 mm, which includes most of our population, Robinson and Wisser (2) were the most appropriate curves. The 95% prediction interval was 9.5 and 10.2 days respectively. Conclusion : Dating pregnancies in every-day practice with GEL is nearly as accurate as prospective studies with only one or two scanners.