Right lateral ventricle is mildly prominent size 10mm of fetus

The size of 10mm regarding either or both lateral ventricles is, to add more to the confusion you already are in, just around the limit what is considered normal. That is why it's very important to continue monitoring the further development, especially because there was no other sign that would point to any kind of abnormality - this just might be some developmental stage at which some things are a little bit out of limits. You will have to have additional ultrasounds, just to make sure, but still, your baby is fine overall - that is why your doctor said you'll have to wait. Baby's development goes at its own rhythm and since there are no major reasons to concern, try to keep yourself calm as much as you can and even though its hard when your baby is in question. Keep us posted on how things go and wish you both the best!