What are the implications for the husband if he discovers a congenital defect in his wife after the marriage contract, and he was not informed of it, and he wishes to divorce?

If your wife has a defect among those that mandate the option of annulment, and you were unaware of it before the marriage contract and did not consent to it after learning of it, then you have the option either to retain her or to annul the marriage, and she is not entitled to any of the Mahr (dowry). However, if the defect is not among those mentioned, then you do not have the option of annulment. If you divorce her before consummation, she is entitled to half of the stipulated Mahr, and if you divorce her after consummation, she is entitled to the full Mahr.