First trimester sonographic dating formula for the Nigerian obstetric population. 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 aims of this study are therefore 3-fold: To derive an ethnic-specific CRL dating formula for the Nigerian population To determine the systematic prediction error of the formula, i. Inclusion criteria were regular menstrual periods between 21 and 35 days in the preceding months before site chicago, last normal menstrual period, and first trimester sonographic dating with fetal CRL measurement. The performance of our best-fit model and derived formula was then tested against those of the nigeria dating published CRL dating formulae in the new set of patients which are as follows: The menstrual age for each fetus was compared with the GA calculated using the three established formulae and the locally derived formula, and the mean difference in estimated GA was used to quantify the systematic prediction error the error that could be expected in the best "point" estimate of GA for a given CRL.