Markandeyapurana 35.48

35.48

eṣa eva vidhirdṛṣṭo janmanyapi hi sūtake /
sapiṇḍānāṃ sapiṇḍeṣu yathāvatsodakeṣu ca //

This same ordinance is applied also to the impurity caused by the birth of sapiṇḍas, among sapiṇḍas and properly among sahodakas also. When a son is born, the father must bathe with his clothes on. And if, after one child has been born there, another should be born, the purification in that case also is prescribed according to the days of the elder-born child.