If the first child is developmentally delayed, the couple can go to the hospital for a chromosome test before getting pregnant, and if the chromosomes are normal, they can have a second child. If the chromosome test is abnormal, it is not recommended to have a second child. 1. Chromosomal normal: chromosomal normal means that both husband and wife are no hereditary diseases, will not be inherited to the second child, in this case you can have a normal second child. 2. Chromosomal abnormalities: chromosomal abnormalities in parents may cause congenital diseases in the fetus, which may cause fetal development delay, developmental abnormalities, and even cause fetal arrest, this situation is not recommended to have a second child. It is recommended to do a good job of physical health checks during the preparation for pregnancy, do not blindly pregnant, there are any abnormalities should be actively seeking medical treatment before preparing for pregnancy.