1.   As many congenital abnormalities can be prevented, these developmental defects should not be considered an irreducible component of perinatal mortality.

2.   Lethal and severe defects together constitute major congenital abnormalities.

3.   Most of these would be as a result of late tests for congenital abnormalities.

4.   Physicians must report children with congenital abnormalities.

5.   Prevalence of each congenital abnormality entity after prevention was calculated from the birth prevalence and the percentage effectiveness of prevention.

6.   Some preventive methods overlap but only one was considered for each congenital abnormality entity.

7.   There is a well established role for termination of pregnancy in certain congenital abnormalities.

8.   The cause is unknown but seems to be related to congenital vascular abnormalities.