The Compendium of Caraka 6.14.5_2

6.14.5_2

tatra dvividho bījopataptau hetuḥ---mātāpitrorapacāraḥ, pūrvakṛtaṃ ca karma; tathā 'anyeṣāmapi sahajānāṃ vikārāṇām/

Here, the cause of the seed's defect is two-fold: the misconduct of the mother and father, and deed done in a previous life; and so it is for other congenital disorders as well.