Infertility – if either partner in a marriage is infertile, there is evidence that early Irish law permitted the other to acquire a child elsewhere. The husband of an infertile wife may thus impregnate another woman in a lower form of marriage. The wife of an infertile husband may likewise leave him temporarily so as to become pregnant by another man. The resultant child is treated as belonging to the husband. A wife may divorce her husband with retention of the bride-price if he is impotent or becomes so fat that he is incapable of intercourse. If the mother of a child develops a wasting-sickness (anbobracht), the father is solely responsible for the rearing of the child, whether he is married to her or not. He is similarly responsible if she becomes leprous (clam) on the grounds that the child may become infected by her sores.
Extract from Medicine and early Irish law by F. Kelly