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Dependence of maternal serum [AFP]/[hCG] median ratios on age of gestation: comparison of trisomy 21 to euploid pregnancies
Author(s) -
MarcusBraun N.,
Birk. O.,
Manor E.,
Segal D.,
Harari G.,
Toma I.,
Shalev S.,
Borochowitz Z.U.,
Yaron. Y.,
Sharony R.,
Itzhaky D.,
Shtoyerman R.,
Appelman Z.,
Braun G.
Publication year - 2009
Publication title -
prenatal diagnosis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.956
H-Index - 97
eISSN - 1097-0223
pISSN - 0197-3851
DOI - 10.1002/pd.2366
Subject(s) - trisomy , aneuploidy , gestation , gestational age , obstetrics , medicine , alpha fetoprotein , down syndrome , human chorionic gonadotropin , gynecology , pregnancy , andrology , biology , endocrinology , chromosome , hormone , genetics , psychiatry , hepatocellular carcinoma , gene
Background Current risk calculations for trisomy 21, which are based on multiples of median (MoM), do not take into account possible differences between euploid and trisomy 21 pregnancies that may develop with gestational age. In order to optimize the predictive value of screening tests, we calculated the ratio between maternal serum concentration of alpha‐fetoprotein (AFP) and that of human chorionic gonadotropin (hCG) in euploid and in trisomy 21 pregnancies. Methods The medians of the concentration ratios, [AFP]/[hCG] at 16–21 weeks of gestation, were plotted as a function of gestational age for 307 cases of trisomy 21 and were compared with the medians of 30 549 normal karyotype cases. Results [AFP]/[hCG] ratio medians were independent of body weight and maternal age. There was a significant difference in the [AFP]/[hCG] ratio when comparing trisomy 21 and euploid pregnancies at each week. This difference became greater with advancing gestational age ( P < 0.01). Conclusion There is a significant difference in ratios of [AFP]/[hCG] between euploid and trisomy 21 pregnancies, which may be used to improve detection rates of Down syndrome screening. Copyright © 2009 John Wiley & Sons, Ltd.