Chinese weight-correction model for maternal serum markers in Down syndrome prenatal screening

Objective: To determine the best weight-correction model by means of analyzing the relationship between maternal weight and maternal serum markers when screening for Down syndrome in China. Methods: Serum levels of (x-fetoprotein (AFP) and free beta-human chorionic gonadotropin (hCG) were measured in 35,917 Chinese women during the second semester of a normal singleton pregnancy and converted to multiple of median (MoM) values. Using 2 methods of statistical analysis, the all-point method and the median regression method, 4 weightcorrection models were then tried, the simple linear, reciprocal, quadratic, and log-linear regression models. Results: The median regression method performed better than the all-point method, and the quadratic regression model showed the best fit for both AFP and hCG in the median regression method, with adjusted R(2)s of 0.987 and 0.988, respectively. Conclusion: The quadratic regression model was found to be the most suitable for Chinese pregnant women. (c) 2006 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.