My sister's fetus' umbilical cord is swollen, should we be worried? is this dangerous?

Hard to tell: In the past I have seen cords very from scrawny thin to very fleshy and thick. The scrawny ones were more associated with troublesome pregnancies.Your use of the term swollen implies a worrisome issue but i don't see it that way.I see it as an incidental finding of uncertain relevance.

Swollen fetal cord: A swollen fetal umbilical cord may indicate a problem her obstetrician may want to do more tests to determine if a problem really exists.