唐氏筛查结果hCGb和AFP值都偏低

出生年龄:1987-09采样孕周:16周4天   体重是57Kg（医院给打成47Kg）  之前一切检查都正常      这次数值有点低标记物         结果        单位       校正MoM       参考范围AFP            24.30      U/mL        0.63          0.7-2.5hCGb           3.674      ng/mL       0.23          0.25-2.5uE3            3.638