Thanks for the query.
with progression of gestational age
the size of uterus increases leading to stretching of the skin over abdomen.
This leads to separation of collagen
fibers which causes dryness and itching.
For more details:http://srsree.blogspot.in/2012/05/itching-over-abdomen-in-pregnancy.html
As liver disease can also cause severe itching
better to get it done blood tests also which will rule out that possibility.