[Multiple birth and Down's disease].

Area of Science:

• Reproductive biology
• Genetics
• Perinatology

Context:

• Down's syndrome (trisomy-21) is a genetic disorder associated with intellectual disability.
• Twinning rates vary significantly across populations and ethnicities.
• Maternal age is a known risk factor for chromosomal abnormalities like Down's syndrome.

Purpose:

• To investigate the frequency of twinning in newborns diagnosed with Down's syndrome.
• To determine if specific types of twinning (e.g., dizygotic vs. monozygotic) are more prevalent in Down's syndrome cases.
• To explore potential contributing factors, such as maternal age, to the observed twinning rates.

Summary:

• The study found a significantly higher frequency of twinning (2.11% +/- 0.6%) in newborns with Down's syndrome compared to the general population (0.73% +/- 0.3%).
• This increase is primarily attributed to a nearly threefold excess in dizygotic (fraternal) twin pairs.
• The elevated rate of dizygotic twins with Down's syndrome is explained by the combined influence of increased dizygotic twinning probability and a higher incidence of trisomy-21 births, particularly with advanced maternal age.

Impact:

• Findings suggest a potential biological link between twinning mechanisms and the occurrence of Down's syndrome.
• Highlights the role of maternal age as a critical factor influencing both twinning and trisomy-21 risk.
• Provides valuable data for genetic counseling and prenatal risk assessment for families with concerns about Down's syndrome and multiple births.