The Compendium of Caraka 4.2.12

4.2.12

raktena kanyāmadhikena putraṃ śukreṇa tena dvividhīkṛtena bījena kanyāṃ ca sutaṃ ca sūte yathāsvabījānyatarādhikena//

By excess of blood she gives birth to a daughter, by excess of semen to a son; / when that seed is divided in two, she gives birth to a daughter and a son, through the excess of one or the other of their respective seeds.