Trisomy 21 mosaicism and maternal age

Area of Science:

• Genetics
• Reproductive Biology
• Medical Research

Background:

• Trisomy 21 (Down syndrome) is a common chromosomal disorder.
• Mosaic trisomy 21 involves a mix of cells with and without an extra chromosome 21.
• Understanding risk factors for mosaic trisomy 21 is crucial for genetic counseling.

Purpose of the Study:

• To quantify the maternal age-specific risk for trisomy 21 mosaicism.
• To compare risk factors between trisomy 21 mosaicism and simple trisomy 21.
• To investigate the role of maternal age and fetal sex in trisomy 21 mosaicism.

Main Methods:

• Utilized data from the National Down Syndrome Cytogenetic Register (1989-2009).
• Analyzed 322 cases of trisomy 21 with mosaicism and 27,943 cases of simple trisomy 21.
• Compared maternal ages and assessed the influence of maternal age and fetal sex on mosaicism.

Main Results:

• Mean maternal age for mosaic trisomy 21 was 33.1 years, versus 35.0 for simple trisomy 21.
• Sixty-seven percent of mosaic trisomy 21 cases showed maternal age dependency, but at a lower risk (0.8%) than simple trisomy 21.
• Thirty-three percent of mosaic trisomy 21 cases were not maternal age dependent, indicating other risk factors.
• Mosaic trisomy 21 was more frequent in females, with no association between fetal sex and maternal age.

Conclusions:

• Maternal age is a significant, yet not exclusive, risk factor for trisomy 21 mosaicism.
• Fetal sex is associated with trisomy 21 mosaicism, independent of maternal age, suggesting other contributing factors.
• Further research is needed to elucidate the non-maternal age-related factors influencing trisomy 21 mosaicism, particularly in relation to fetal sex.