Hi yes very much necessary. Baby's internal parts will be seen to check if there is any issues.

It can be delayed for a week or more.. but you should do it.

<span style="color:#3B5998;"><b><a href="http://app.babychakra.com/article/3395">Scans Recommended For Every Mom During Second Trimester</a></b></span>

Yes it is if adviced by doctor