Anatomy ultrasound

I am 21w3d and had my anatomy ultrasound yesterday. Baby is a healthy baby boy but they told me there is a problem w the umbilical cord. If I remember correctly what the dr told me (I was stressed and freaking out obv) there are supposed to be 2 veins and 1 artery in the umbilical cord to support baby. In mine, there is only 1 of each. I haven't done much research on it yet but he says usually baby is fine. I have to make an appt to go see a high risk specialist for another ultrasound. Anyone else currently going through this/ had this before and what was the outcome? I'm so worried now. 😟