Understanding Slightly Enlarged Lateral Ventricles in Fetal Brains

Question
Hello Dr Rappaport,

I am now 41 yo and pg with my first baby (17 weeks).  I had the integrated screen results today as well as the Level II ultrasound.  All blood results were good except for downs syndrome that came back at 1:100, basically no real difference compared to age related risk.

All looked great on u/sound too except that the lateral brain ventricle was slightly enlarged.  The technician said that this is sometimes seen in boys but it caught the attention of the Dr as being still larger even though we are having a boy.  We have an amnio scheduled for tomorrow.  The nuchal results at 11 wks were good (1.1 mm).

I am scared silly about this and so very upset.  I am petrified that we just saw a soft marker for downs syndrome on our son ...

I wonder if this increases our 1:100 risk given from the blood results ?  Do you commonly see a slightly enlarged brain venticle and if so, how often is this associated with downs syndrome ?

Thankyou for taking the time, I am pretty distraught at the moment.
Regards
Teresa

Answer
If the AFP result is age appropriate, the nuchal transluscency test was normal, and the level II ultrasound showed no "soft" signs of chromosomal abnormalities, I doubt that you should worry, even with a slightly enlarged lateral ventricle. An amnio will give you 100% assurance and a diagnosis if something is there, so do not be upset. I do not put too much credence in "soft" signs of defects because there are too many false positives. The amnio is the definitive test and is recommend for women over the age of 35 even with no risk factors or "soft" signs on sonogram. Be patient, and good luck on the rest of the pregnancy.