RESUMO
INTRODUCTION: Estimation of the risk of Down syndrome pregnancy by the triple marker test is performed on women once at anytime during the 15-21 weeks of gestational age. The triple marker test is based on the distribution of the alpha-fetoprotein (AFP), chorionic gonadotropin (CG) and unconjugated estriol (uE3) of the different pregnancy. In spite of the logical excellencies, various factors can affect the result of the test in practical field. We compared differences of the risk of Down syndrome pregnancy based on the specimen obtained from two visits during the 15-21 weeks of gestational age. METHOD: We measured the AFP, CG and uE3 with Access (Beckman Coulter, USA) from the sera of 104 pregnant women who visited two times about 2 weeks of interval during 15-21 weeks of gestational age. We calculated log (MoM) of AFP, CG and uE3 of each marker between two visits, and compared differences of each biochemical marker and difference of risk of Down syndrome pregnancy between two visits. RESULT: Mean+/-SD of log (MoM) of AFP, CG, uE3 of the 1st visit were 0.019+/-0.156, -0.016+/-0.224, 0.002+/-0.138, respectively, and those of AFP, CG, uE3 of the 2nd visit were 0.010+/-0.140, -0.076+/-0.205, 0.057+/-0.138, respectively. CG and uE3 showed statistically significant difference (P<0.001, P<0.001, respectively) but AFP did not (P=0.328). Risk of Down syndrome pregnancy of the 1st visit was 8.017x10(-4)+/-1.6241x10(-3), and that of the 2nd visit was 5.667x10(-4)+/-1.6241x10(-3), with no significant difference statistically (P=0.094). CONCLUSION: The risk of Down syndrome based on the sera of woman who visited two times about 2 weeks of interval between 15-21 weeks of gestational age did not show significant difference. It is resonable that triple marker test is performed on women once at anytime during the 15-21 weeks of gestational age in practical base.