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ISRN Obstetrics and Gynecology
Volume 2012 (2012), Article ID 938583, 6 pages
Research Article

Ultrasound Reference Chart Based on IVF Dates to Estimate Gestational Age at 6–9 weeks’ Gestation

1Department of Obstetrics and Gynaecology, Monash University, Clayton, VIC 3168, Australia
2Mercy Hospital for Women, University of Melbourne, Heidelberg, VIC 3084, Australia
3Springfield Hospital, Lawn Lane, Essex, Chelmsford CM1 7GU, UK
4Monash Ultrasound for Women, Monash Surgical Private Hospital, Clayton, VIC 3168, Australia
5Monash IVF, Monash Surgical Private Hospital, Clayton, VIC 3168, Australia

Received 3 April 2012; Accepted 14 May 2012

Academic Editors: A. Martin-Hidalgo, G. Rizzo, and K. Yang

Copyright © 2012 Pavitra Delpachitra et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Accurate determination of gestational age underpins good obstetric care. We assessed the performance of six existing ultrasound reference charts to determine gestational age in 1268 singleton IVF pregnancies, where “true” gestational age could be precisely calculated from date of fertilisation. All charts generated dates significantly different to IVF dates ( 𝑃 < 0 . 0 0 0 1 all comparisons). Thus we generated a new reference chart, The Monash Chart, based on a line of best fit describing crown-rump length across 6 + 1 to 9 + 0 weeks of gestation (true gestational age) in the IVF singleton cohort. The Monash Chart, but none of the existing charts, accurately determined gestational age among an independent IVF twin cohort (185 twin pairs). When applied to 3052 naturally-conceived singletons scans, The Monash Chart generated estimated due dates that were different to all existing charts ( 𝑃 ≀ 0 . 0 0 4 all comparisons). We conclude that commonly used ultrasound reference charts have inaccuracies. We have generated a CRL reference chart based on true gestational age in an IVF cohort that can accurately determine gestational age at 6–9 weeks of gestation.