Mixed outcome. Abortion is gradually dropping because of fewer service providers and lagging demand. The GOP panders to its evangelical subset who oppose any aspect of what they consider abortion. However this issue is a great vote and money gainer. The republicans controlled both house, Senate and presidency during the Bush years and did not pass a single abortion bill. They value the votes and money more.
No one knows. Not all republicans are opposed to abortion. If any governments choose to limit accesses to contrception, and more undesired pregnancies occur, then abortion rates may even increase. Republicans ruled during several recent administrations without significant changes in abortion rates. Ideally, every pregnancy should be planned for, desired, and welcomed.