So janmanā jāyate śūdraḥ saṁskārād bhaved dvijaḥ. Birth. Birth is not all, everything. The culture, saṁskāra. Saṁskāra means culture. One has to take his birth, rebirth, by culture, by education, by knowledge. That is called cultural birth. So unless one is in the cultural birth, he is to be considered the lower grade person, or the śūdra.
So therefore the system in the, according to varṇāśrama-dharma, that not only by birth, before birth, when the father and mother is going to be combined to beget a child, there are cultural saṁskāras or reformatory measures. How much carefully these things are. They wanted first-class son, not sons like cats and dogs, first-class son. So there is some saṁskāra. There is some purificatory measures, which is called garbhādhāna-saṁskāra. Garbhādhāna means pregnancy, the cultural ceremony before making the mother pregnant. And it is enjoined, you will find in the Bhāgavata, that any family, the brāhmaṇas, the kṣatriyas and vaiśyas, if they give up this garbhādhāna-saṁskāra, birth-giving ceremony, then that family turns immediately to the classification of the śūdras.