Bmus fetal size and dating
The scatter plot of the raw data for the best-fit fractional polynomial regression model showing the estimated GA by CRL expressed in days and mm, respectively, for the first group of 322 subjects is shown in [Figure 1].
The hospital records of 322 pregnant women who presented for early booking in the first trimester were reviewed.The Korean formula has the largest systematic error, of overestimation of about 4 days (i.e., 0.572).In this study, we established a dating formula for use in the Nigerian population for accurate first trimester dating of naturally conceived pregnancies that had lower systematic prediction error than for established formulae.It has been shown that ethnicity has a significant influence on fetal biometry, the published CRL dating formulae are derived predominantly from Caucasian population and may not be applicable in our environment.
The study was a two-stage procedure; the first stage was to develop a formula establishing a local reference for GA (in weeks) and the CRL (in mm).The estimated GA was calculated from the Last Menstrual Period (LMP) and corrected for cycle length for each CRL. At the point of measurement we ensured that the fetus was horizontal on the screen so that the line between crown and rump was 90 to the ultrasound beam.