Any mom here knows "Enlarged Cisterna Magna"

I was instructed to do another ultrasound in 6 weeks as a precaution follow up. In the 20 weeks' ultrasound,the baby's cisterna magna appears to exceed the 10 mm upper limit.
I did my research online for Enlarged Cisterna Magna, which seems to indicate potential abnormal chromosome. Has anyone had such issue before, how was your baby turned out? I am eager to hear your story.

Thanks!