sa tat pum-savanam rajñi
prasya vai patyur adadhe
garbham kala upavrtte
kumaram susuve ’praja
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Although the Queen had no son, after eating that food, which had the power to produce a male child, she became pregnant by her husband, and in due course of time she gave birth to a son.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Among the ten kinds of purificatory processes, one is pum-savanam, in which the wife is offered some prasada, or remnants of foodstuff offered to Lord Visnu, so that after sexual intercourse with her husband she may conceive a child.