title: Sonographic nuchal markers for Down syndrome are more common but less ominous in gestations with a male fetus.
abstract: OBJECTIVE
  A change in the normal male-to-female ratio has been reported in some autosomal trisomies (i.e., trisomy 21 or trisomy 18). The objective of the present study was to evaluate the male-to-female ratio in pregnancies with sonographic nuchal markers for Down syndrome.
  
  
  METHODS
  The results of amniocenteses performed for isolated nuchal markers for Down syndrome were grouped by fetal sex and by maternal age. The male-to-female ratio in normal and trisomic gestations was compared.
  
  
  RESULTS
  584 fetal karyotypes were available for analysis. A significantly higher male-to-female ratio was observed. More affected gestations were observed in association with a female fetus. These differences were mainly attributed to the group of patients younger than 35 years that represents more than 80% of our study population. No difference was observed in pregnancies of patients older than 35 years of age.
  
  
  CONCLUSIONS
  In patients younger than 35 years, sonographic nuchal markers for Down syndrome are more frequent (but apparently less ominous) in gestations with a male fetus. If the gender is known, counseling can be modified to include such differential risks.
authors.affiliation: Department of Obstetrics and Gynecology, Rambam Medical Center, Haifa, Israel. a_drugan@rambam.health.gov.it
authors.forename: A
authors.initials: A
authors.lastname: Drugan
authors.forename: A
authors.initials: A
authors.lastname: Weissman
authors.forename: R
authors.initials: R
authors.lastname: Avrahami
authors.forename: R
authors.initials: R
authors.lastname: Zamir
authors.forename: M I
authors.initials: MI
authors.lastname: Evans
mesh_terms: D000328:Adult; D004314:Down Syndrome / Q000000981:diagnostic imaging* / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D011247:Pregnancy; D012307:Risk Factors; D012744:Sex Ratio; D016216:Ultrasonography, Prenatal