Diagnosis of sex chromosomal abnormalities in neonatal intensive care units

Neonates are hospitalized in the neonatal intensive care unit for complications arising during delivery or for the treatment of congenital anomalies. Some anomalies may warrant chromosomal analysis. We investigated all cases of neonates hospitalized in the NICU at Dokkyo Medical University Hospital between January 1990 and May 2011. Over the study period of 21 years and 5 months, 169 of 6,159 neonates (2.74%) were diagnosed with chromosomal abnormalities. Autosomal chromosomal aberrations were observed in 165 neonates (2.68%), and sex chromosome abnormalities in only 4 neonates (0.07%). Compared with previous studies, we found a much lower prevalence of sex chromosome abnormalities, despite a similar overall prevalence of chromosomal abnormalities. This seems to be due to the fact that sex chromosome abnormalities are likely to be clinically invisible in the NICU.