Some, because they were ignorant of what was really happening, may have done so thinking they were really not putting an end to a human life. It is done in some cases to hide immoral conduct. In other ways it is done because someone does not want the burden of having to raise a child at this time in their life. There may then be many reasons why a woman would chose this course of action. God spoke to Israel about what they should know before they entered Canaan. He did not want them to behave like those in Canaan, hence destroy all their idols and places of worship. One thing that those in Canaan engaged in was to burn their own children in fire to Molech. God did not give His permission for them to do that to their children; so drive out the Canaanites (Leviticus 18:21).
One of the great blessings in coming to Jesus the Christ is the forgiveness of sins (Acts 22:16). Paul was guilty of condemning Christians to death and Onesimus was a runaway slave (Acts 26:10; book of Philemon). There is no sin that cannot be removed by the blood of Christ (Ephesians 1:7). After one becomes a Christian, there is no sin that cannot be dealt with by that same blood (I John 1:7). The difficult part would be to admit the wrong that has been done. If the knowledge of the act is private then under the law of Christ we have no man on earth who intercedes for us. Our Advocate is Jesus the Christ and in non public matters we can go to Him in the “privacy of our closet” and find forgiveness.
It may also be true in our times that a person does not have to confess the wrong. That is unscriptural. We do confess to God whether in private or public, the departure from His way. If we confess, forsake, then we can arise to live or begin anew a new life in Christ Jesus. There is then no sin that cannot be forgiven with the result of the person finding peace in Jesus (Romans 5:1).