Let’s start with the belief that life starts at conception. With this belief, a fetus is equivalent in protection to a newborn. Following this, voluntarily ending it is murder.
Then what about miscarriage? If a newborn were to die under unknown circumstances, there should be an investigation. Should then all pregnant people be investigated for potential negligence or abuse for this already traumatizing situation? 1/3 to 1/2 of all fertilized eggs never implant. Should these be scrutinized? I cannot see how one can say a fetus and newborn deserve equivalent protections and then fail to give them.
Further, what about support for abortion exceptions for incest or rape? If the pregnancy in this scenario went to term and the child was born, one wouldn’t then support that murdering the newborn was OK.
If you don’t believe these things, then you don’t believe newborns and fetuses deserve equal protection. You only happen to believe specific fetuses deserve one specific protection.