How does apoptosis aid in normal embryo development?

Apoptosis - programmed cell death - is very important in embryo development. DNA replication is not 100% error proof. Since embryo development calls for a high rate of DNA duplication due to the numerous cell divisions occurring in the embryo as it develops, some cells may bear some DNA mutations due to error in DNA duplication by DNA polymerase. The cells have mechanisms to detect such errors and if they are irreparable, apoptosis is initiated, destroying these damaged cells. This protects the integrity of the embryo ensuring cells with damaged DNA do not divide and result in abnormalities.