Is it permissible for the husband to go to bed with his wife after the expiration of her Nifas (bleeding that…

Is it permissible for the husband to go to bed with his wife after the expiration of her Nifas (bleeding that occurs after childbirth, miscarriage, or abortion), which is ten days, and the continuation of discharge of an Istihadha type, noting that bleeding continued for some eighteen days?