Recurrent Miscarriage

Question 1

What percentage of recognised pregnancies miscarry? Of these, what percentage are chromosomally abnormal?

Answer 1

~15-20%, of which 50% are chromosomally abnormal

Question 2

If a particular trisomy recurs in a couple, what may there be a risk of?

Answer 2

Gonadal mosaicism

Question 3

How do miscarriages occur in the context of balanced rearrangements?

Answer 3

The balanced rearrangement is passed on in unbalanced form to the egg or sperm resulting in a genetically unbalanced conception

Question 4

When is there a risk of having abnormal children when an inverted chromosome is involved?

Answer 4

If the inverted segment is big, includes the centromere and the end sections are very small

Question 5

What are the product differences between the inversion loop in a paracentric and pericentric inversion?

Answer 5

• both produce a Normal chromosome and an Inverted chromosome
• a pericentric inversion produces dup p distal and dup q distal recombinant chromosomes
• a paracentric inversion produces dicentric and acentric recombinant chromosomes

Question 6

In what scenario may an apparently balanced translocation carrier be clinically abnormal?

Answer 6

If the translocation breakpoint disrupts a gene

Question 7

What is the purpose of segregation analysis?

Answer 7

To assess whether there is a risk of balanced translocation carriers having liveborn unbalanced offspring or whether all unbalanced products will miscarry