Karyotyping - is it done to check all pregnant women over age 35years?

Not always. The decision to do an amniocentesis in order to do karyotyping is a personal decision and carries up to a 1 in 200 miscarriage rate. The information obtained would classically be used to decide upon termination or not as there is no treatable or correctable chromosome abnormality. At 35 years old and above, the risk of a chromosome defect is 1 in 200 or greater.