Actually, I think it is the 9th and 14th amendment, which states
"No State shall deprive any person of life, liberty, or property, without due process of law." Not allowing a woman to have an abortion is in violation of that. I have also read that when the Supreme court made it legal, they mentioned that a fetus is considered the woman's property and therefore, she can terminate it if she wishes. But when Norma McCorvey wanted to have an abortion, it was because she was raped. I think she only wanted to make it legal in certain circumstances, not like it is now. I found it interesting that after she became prolife, she made the following statement to congress,
"It was my pseudonym, Jane Roe, which had been used to create the "right" to abortion out of legal thin air. But Sarah Weddington and Linda Coffee never told me that what I was signing would allow women to come up to me 15, 20 years later and say, "Thank you for allowing me to have my five or six abortions. Without you, it wouldn't have been possible." Sarah never mentioned women using abortions as a form of birth control. We talked about truly desperate and needy women, not women already wearing maternity clothes."