Question

why few foetus with chromosomal trisomies survive to birth

Answer 1

Explanation:

But if meiosis doesn't happen normally, a baby may have an extra chromosome (trisomy), or have a missing chromosome (monosomy). These problems can cause pregnancy loss. Or they can cause health problems in a child. A woman age 35 years or older is at higher risk of having a baby with a chromosomal abnormality.

Answer 2

Answer:

likewise, almost all fetuses with autosomal trisomies die before birth ... those that survive usually have multiple physical malformations , mental retardation and relatively short lives. the most well known and most common autosomal abnormality is down syndrome.