manifestation of connective tissue disorder in utero?

I am 36 years old and 27 weeks pregnant. My baby was diagnosed with a dilated ascending aorta at 22 weeks gestation. Only the aorta is dilated, the valves, root and walls of the aorta are fine. So is the blood flow. The z score is 2.3 at 22 weeks. (5.3mm).  The widest point of the aorta had grown from 5.3mm to 6.2mm in 5 days.   My partner and I have no sign or immediate history of a connective tissue disorder or BAV. The baby does not have a bicuspid vavle either.  Has anyone evercome across anything like this? My cardiologist siad this is very rare to see in utero.  I have another scan next week to see how much it has grown.  My first baby has down syndrome and a hole in her heart, I have been told that this is no way connected and is most likey a connective tissue disorder of some kind.  we are having a test done on the baby for marfans syndrome but this will take a month for the results and could be inconclusive.  I am so worried and would appreciate any information or knowledge anyone has.