What should I do, as I committed adultery with a Christian woman and feared she might become pregnant, so I asked her to marry me, but she refused, saying that if she gets pregnant, she will not abort the child?

Adultery is one of the most heinous sins, but Allah accepts sincere repentance, which is achieved by refraining from the sin, regretting it, and resolving not to return to it, while concealing oneself. Marriage to the woman with whom one committed adultery is not a condition for repentance. If you repent sincerely, Allah will forgive you, and the child resulting from adultery will not be attributed to your lineage. Occupy yourself with achieving repentance, drawing closer to Allah, and marrying a righteous woman.