Single Artery Umbilical Cord?

Christy • Mommy of Hunter, Madalynn, and our angel baby Blake born sleeping at 39w. Our rainbow baby girl is due July 15, 2016!
Yesterday during my second anatomy scan (because our baby boy would not cooperate during the first) they saw that the umbilical cord has only one artery instead of two. Now we are being referred to a specialist and I am so worried now that something maybe wrong or something is going to happen. Is anyone else going through this???