All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
You and the woman mentioned in your question should hasten to make a sincere repentance from adultery. It is a heinous and great sin. It is reported from Ibn Mas'ood that he asked the Prophet said: "O Allaah's Apostle! Which is the most hideous sin?" He said, "To set up rivals to Allaah by worshipping others though He alone has created you". I asked, "What is next?" He said, "To kill your child lest it should share your food". I asked, "What is next?" He said, "To commit illegal sexual intercourse with the wife of your neighbor."
The punishment you deserve, if you declare your adultery, is to be stoned till death, if both of you were ever a married and consummated the marriage. If you are not married then the punishment is to be flogged with a hundred stripes and exiled for a year. The evidence is that 'Ubaadah Ibn As-Saamit said that the Prophet said: "If a virgin male commits fornication with a virgin female, flog them with a hundred stripes and exile them for a year. If two people commit adultery and none of them is virgin flog them with a hundred stripes and pelt them both with stones to death." [Muslim]
But you have to conceal your sin; declaring sin is not a condition for the acceptance of the repentance. The Prophet said: "Whoever was inflicted by (committing) any of these dirts (i.e. sins), he should hide his sins and conceal them just as Allaah did not expose his sins." [Al-Haakim and Al Bayhaqi]
As for aborting the fetus or inciting the woman to take divorce from her husband, are additional sins and evils. So, you should not think about them at all.
The Prophet said: "Any woman who seeks divorce from her husband without being harmed in any way the smell of
Aborting the fetus without any reason that is acceptable in Islam is forbidden even if it is before infusing life in the fetus. Abortion after the life has been infused is a killing an innocent soul. So, it is not permissible to have an abortion during a certain stage; it is considered as a major sin.
Know that the child is traced back to the husband as long as he does not deny him by performing Li'aan' (the separation occurred after taking an oath by both the husband and the wife when he accuses his wife of committing illegal sexual intercourse). The Prophet said: "The boy is for the owner of the bed and the stone is for the person who commits an illegal sexual intercourse." [Al-Bukhari and Muslim]
In brief, you have to make sincere repentance, keep away from this woman. She is also required to do the same; conceal her sin and should not abort the fetus. The child will be traced back to the husband.
Allaah knows best.