I understand. Roe doesn't set any threshold for making abortion illegal. It says states cannot prohibit abortions the first trimester, they can regulate but not prohibit the second trimester, and can prohibit the third trimester. It is up to the states whether they do so or not.
Roe was based on viability, and since medical science has extended viability, it would make sense to lower it. However, one reason I didn't like Roe was because I don't think the Constitution sets any time limits for such an issue--that is a reason stretch for the court to suggest that is a constitutional issue.
The right to privacy would be one such example. It's between the woman and her doctor.