Modern medical science has nothing to do with pregnancies lasting 9 months. Full fetal development is at 9 months. The heart isn’t even developed until about 4 weeks and not detectable until around 6 weeks by ultrasound. Sometimes we can’t even see a heartbeat at that point. I’m an ultrasound tech, I scan them every day. Birthday is in regard to the day you’re born. Which, you know, you just decided to post this to rage bait.