Second-trimester diagnosis of complete trisomy 9 associated with abnormal maternal serum screen results, open sacral spina bifida and congenital diaphragmatic hernia, and review of the literature.

OBJECTIVES

To present the prenatal diagnosis of complete trisomy 9 and to review the literature

CASE

A 25-year-old primigravida woman was referred for amniocentesis at 19 weeks' gestation because of abnormal maternal screen results showing an elevated maternal serum alpha-fetoprotein (MSAFP) level and a low maternal serum free beta-human chorionic gonadotrophin (MSfreebeta-hCG) level.

RESULTS

Genetic amniocentesis revealed a karyotype of 47,XX,+9 in the amniocytes and an elevated amniotic fluid AFP level. Ultrasonography demonstrated intrauterine growth restriction, left congenital diaphragmatic hernia, fetal ascites, a sacral spina bifida, a horseshoe kidney, and absence of amniotic fluid. Ultrafast magnetic resonance imaging scans further depicted detailed anatomical configurations of the major congenital malformations. The pregnancy was terminated subsequently. The proband postnatally manifested characteristic facial dysmorphism, limb deformities, and an open sacral spina bifida with myelomeningocele. Cytogenetic analysis of the skin fibroblasts revealed a karyotype of 47,XX,+9. Molecular studies of various uncultured fetal tissues using microsatellite markers confirmed a diagnosis of complete trisomy 9 resulting from a meiotic I nondisjunction error of maternal origin.

CONCLUSION

Complete trisomy 9 can be identified prenatally with advanced maternal age, sonographically detected fetal structural abnormalities, and abnormal maternal serum screen results. Fetuses with complete trisomy 9 may be associated with congenital diaphragmatic hernia, an open sacral spina bifida, elevated MSAFP, and low MSfreebeta-hCG. We suggest detailed prenatal imaging investigations and genetic analyses of multiple fetal tissues when a prenatal diagnosis of trisomy 9 is made.