OK, so, hypothetical: Let's say there was a law passed that banned all abortions after two weeks.
Now, that's not the ideal situation. We'd rather a law that banned all o them. That said, it is certainly the case that anyone who waited longer than 2 weeks would not get a chance to have an abortion. Which would be a lot of people. Many children would be saved. Would you dispute this?
As 20 weeks, its so late that it barely matters. That said, those few people who would actually otherwise wait longer than 20 weeks might find out that its too late.
If we legalized the murder of children up until age 5, do you think that some parents would have "More time to decide" and so would spare their children? The answer is that its irrelevant. The unfortunate fact that the murder of some kids is legal is no excuse for keeping the murder of even more kids legal. I support this law. It sucks, its useless, but passing the law is better than not passing it.