Prenatal diagnosis of mos45,X/46,X,+mar in a fetus with normal male external genitalia and a literature review

Taiwan J Obstet Gynecol. 2009 Sep;48(3):292-5. doi: 10.1016/S1028-4559(09)60307-7.


Objective: Prenatal diagnosis of mos45,X/46,X,+mar is difficult in genetic counseling. Patients with the presence of a Y-derived marker may manifest male or female external genitalia. Here, we report a fetus with phenotypically male external genitalia of mos45,X/46,X,+mar. In addition, the cases with prenatally detected mos45,X/ 46,X,del(Y)(q11.2) and normal male external genitalia are reviewed.

Case report: A 30-year-old, primigravid woman was referred for amniocentesis because of an abnormal Down syndrome screening result at 20 weeks' gestation. Cytogenetic analysis showed mos45,X/46,X,+mar without a normal Y chromosome. Prenatal ultrasound detected symmetric intrauterine growth restriction and normal male external genitalia. After termination of the pregnancy, a phenotypically normal male fetus was delivered smoothly without apparent structural defects. Based on conventional G-banded analysis, the marker chromosome appeared as a Y chromosome that originated with a deleted Yq, designated as del(Y)(q11.2).

Conclusion: Based on a literature review, the addition of fluorescence in situ hybridization and molecular analysis to the conventional cytogenetic techniques can provide more accurate identification of a Y chromosome aberration in the prenatal detection of mos45,X/46,X,+mar, thus allowing more appropriate genetic counseling for the family.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Adult
  • Chromosomes, Human, X
  • Chromosomes, Human, Y
  • Female
  • Genetic Markers*
  • Genitalia, Male*
  • Humans
  • In Situ Hybridization, Fluorescence*
  • Male
  • Pregnancy
  • Prenatal Diagnosis*
  • Sex Chromosome Aberrations*


  • Genetic Markers