Jahm bin Dinar (may Allah have mercy on him) narrates from Ibrahim (may Allah have mercy on him) that when a man declares himself a liar after the li'an, he is to be given the prescribed punishment, the child is to be attributed to him, and the two of them will never be together again.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب اللعان / 15360