I just read an article earlier about a woman who ran a marathon and then started feeling weird after, she assumed she over exerted herself and went to the hospital to get a check up and they found a fetal heatbeat. She ended up having the baby within five minutes of being set up in a room!
There is a show called I didnt know I was pregnant. It is pretty interesting. Some women go up to the birth without realizing they are pregnant. Strange I know!
One of my friends had her period every month while she was pregnant with both of her kids. Not sure why and doctors didn't either...apparently that's normal for her. But she found out at 10 wks because of morning sickness.