What is the difference between a woman's right to an abortion and the right to postpone it?

The abortion decision is different not only because [ ] a pregnancy decision fundamentally affects the subsequent course of a woman's life, but also because, unlike a decision concerning marriage or sterilization [ ], the abortion decision is highly time sensitive. Although marriage and sterilization can be postponed to adulthood, the option of abortion "effectively expires in a matter of weeks from the onset of pregnancy." (Bellotti v. Baird, supra, 443 U.S. 622, 642, 99 S.Ct. 3035, 3047, 61 L.Ed.2d 797.) "[T]he abortion decision is one that simply cannot be postponed, or it will be made by default with far-reaching consequences." (Id. at p. 643, 99 S.Ct. at p. 3048.)