The Compendium of Bheḷa 4.3.1

4.3.1

ihāsamānagotrāntu[vai] ṛtusnātāṃ striyaṃ vrajet | medhāvinamarogaṃ[di-] sā putramevaṃ prasūyate ||

Here, one should approach a woman of a different gotra who has bathed after her fertile period; / thus she gives birth to an intelligent, healthy son.