Estimates run from 50 to 80 percent, and even some implanted embryos spontaneously abort. The woman might never know she was pregnant.
Assuming that fertilization and implantation all go perfectly, scientists can reasonably disagree about when personhood begins, says Gilbert. An embryologist might say gastrulation, which is when an embryo can no longer divide to form identical twins. A neuroscientist might say when one can measure brainwaves.
airhogg t1_jegt3c7 wrote
Reply to Okay, which one of you took your snow tires off? by aqhamills
I did mine this morning