The influence of maternal weight on human chorionic gonadotropin in the multiple-marker screening test for fetal Down syndrome

Blood levels of human chorionic gonadotropin (hCG) in pregnant women may vary according to women's weight and volume of distribution. An abnormally high level of hCG may indicate a fetus with Down syndrome. Researchers reviewed two genetics databases for cases of women with high hCG levels. Women who weighed over 180 pounds and who were 30 years or older were more likely to have falsely low screen positive rates for hCG levels as compared to women of the same age range weighing less than 180. A weight correction formula effectively distributed the positive screening findings more evenly by age and weight group. The weight correction formula did not change the detection rate of Down syndrome but may prevent underestimation of Down syndrome risk in older pregnant women.