Re: Start of pregnancy
When they calculate fetal age (which is 38 weeks average), they do it based on conception.
My understanding is that the original OBGYN definition of pregnancy started at conception, and it was changed to implantation so that things like the pill were not considered abortion-inducing. So, yes, there are a whole bunch of moral and political implications based on how you answer that question.
Creighton Model FertilityCare Teacher
Helping others to appreciate their fertility whether trying to avoid or conceive