First trimester sonographic dating formula for the nigerian obstetric population
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Abstract
Objective: The main purpose of this study is to derive a dating formula for the Nigerian obstetric population, quantify its prediction error, and compare its performance with existing published formulae.
Materials and Methods: The crown-rump length (CRL) of 322 fetuses without risk for fetal growth restriction were plotted against menstrual age to obtain a scatter plot from which we derived the best-fit fractional polynomial regression model for estimating gestational age (GA). The accuracy of the formula was compared with that of existing formula in another data set of 88 fetuses.
Results: The scatter plot yielded a best-fit equation for the estimation of GA (in weeks) from CRL (in mm) as GA=−0.0008 (CRL2) + 0.168 CRL + 5.397, (R2=0.8017). The mean prediction error was 0.13 for our formula, and 0.16 and 0.20 for Nelson’s, and Robinson’s formulae, respectively.
Conclusion: Our dating formula locally derived was more favorably applicable for the Nigerian population. This has implication for prenatal diagnosis in Nigeria.
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