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 alpha-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 weight-correction 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.