Yes, there would be a risk of defects in wanted pregnancies, in contraceptive failures or sexual assault. As for anatomy during pregnancy, the mothers body DOES see the fetal placenta as foreign, which is why the immune system is suppressed by various mechanisms during pregnancy, so thar her body doesn't attack the fetus. My background is biochemistry and embryology so I DO know a lot about anatomy and maternal vs fetal behavior. The most practical and kind approach would be for anti choice people to not interfere in things they know nothing about. Let the doctor and the woman make decisions about her life and body.