We describe new charts and tables for dating pregnancies derived from
data collected in a study designed to enable the construction of these
and charts of fetal size. This was a prospective study in which 663 f
etuses seen in the routine ultrasound clinic in a London teaching hosp
ital were scanned once only for the purpose of this study. We discuss
the statistical methodology in detail and compare the new charts with
other published charts. We suggest that the differences seen may be du
e to variation in study methodology.