I didn't have that with any of my pregnancies, but I have read that it's not that uncommon, and you certainly don't have to have diabetes to have it.
If everything else looked good with baby, then that sounds positive
When I was pregnant, I looked at sites about health problems in pregnancy (because I wanted to read about mums with diabetes) and I saw a number of women who had a single umbilical artery. Of course, it's far better to speak to your consultant than look on Google, but none of those women had diabetes so it can happen to anyone, as I understand it.
Wishing you all the best X