Medknow Publications on behalf of Indian Society of Human Genetics
Abstract
Background: Down syndrome (DS) and sex chromosomal aneuploidy (SA) are
common chromosomal anomalies causing congenital malformations and
mental retardation in humans. The well-established risk factor,
advanced maternal age, was not found in many of the DS and SA cases in
India, while the other possible risk factors have not been well
studied. In view of this, the present study has been made. Materials
and Methods: During the last 5 years, 150 clinically suspected DS and
25 SA cases were referred to our laboratory for chromosome
investigation from major hospitals of Mysore city. Chromosome
preparations were made from these patients after informed consent was
obtained. Well-spread G-banded metaphase plates were analyzed by
automated LEICA KARYO software. Two hundred and 100 randomly selected
families belonging to different religions were used as controls for the
DS and SA cases, respectively. Statistical analysis was carried out
using logistic regression Results: Out of the 150 cases of DS, 122 had
free trisomy 21, two were mosaic trisomy 21, and one had translocation.
Logistic regression of case-control study of DS children revealed that
the odds ratio of uncle-niece marriages, or second cousin marriages, or
parents lived in rural region, or exposure of the parents to chemicals,
or parents education status, or habits (tobacco/ alcohol used) of
father, or mother not undergone prenatal scanning, or mothers with
previous abortions were significant when all the variables of that
category were used one at a time. Exposure of the parents to chemicals,
parents\u2032 educational status, habits (tobacco/alcohol use) of the
father, mother not undergone prenatal scanning, and history of previous
abortions were significant when all the variables of that category were
used one at a time. Similarly, except for consanguinity, history of
previous abortions, and mother not undergone prenatal scanning, all
other factors showed significant odds ratios in SA cases. Conclusion:
Besides the known risk factors, consanguinity, region (rural/urban) of
residence of parents, exposure of parents to chemicals, educational
status of parents, habits of father, prenatal scanning, and
reproductive performance of mother are possible risk factors for
chromosomal aneuploidy