I found out at my 20 week anatomy scan that my daughter has only one artery in her umbilical cord, just like my first child ( I didn't find out about this until I left the army and received an ultrasound at 37 weeks since I was high risk). She was originally measuring two days behind at all of our ultrasounds but at the 20 week she measured eight days behind which is very similar to my first born. They checked her heart which has all four chambers and the circulation is good, her organs are all present and in the right place everything looks good so I try not to worry. I am wondering since this is my second child that if having children with one artery is a natural occurrence for me? All of the girls born on my mother's side are small. Usually between 5 pounds flat and 6 and a half pounds. My mother said measuring behind is to be expected herself including my grandmother experienced it with all the girls while the boys were all eight pounders but they don't remember anything about the umbilical cords.