Agniveshyagrihyasutra 2.1.2.2

2.1.2.2

prathamagarbhāyāścaturthe māsyāpūryamāṇapakṣe puṇye nakṣatre agnimupasamādhāya vyāhṛtiparyantaṃ kṛtvā dhātā dadātu no rayim iti catasro dhātrīrjuhoti \

For a woman pregnant for the first time, in the fourth month, in the waxing fortnight, under an auspicious lunar mansion, having set up the fire, having performed [the ritual acts] up to the mystic utterances, he offers four Dhātṛ oblations with, 'May Dhātṛ give us wealth.'