Dependence of maternal serum [AFP]/[hCG] median ratios on age of gestation: comparison of trisomy 21 to euploid pregnancies

N. Marcus-Braun, O. Birk, E. Manor, D. Segal, G. Harari, I. Toma, S. Shalev, Z. U. Borochowitz, Y. Yaron, R. Sharony, D. Itzhaky, R. Shtoyerman, Z. Appelman, G. Braun

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


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.

Original languageEnglish
Pages (from-to)1130-1134
Number of pages5
JournalPrenatal Diagnosis
Issue number12
StatePublished - 1 Dec 2009
Externally publishedYes


  • AFP
  • Down syndrome
  • Gestational age
  • Maternal serum markers
  • Trisomy 21
  • hCG

ASJC Scopus subject areas

  • Obstetrics and Gynecology
  • Genetics(clinical)


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