Well, that is a good guess...
Carpal Tunnel Syndrome (CTS) involves the median nerve where it is
compressed at the site where it courses through a tight fascial
sheath in the palmar aspect of the hand. In pregnancy, accumulation
of fluid in that area will cause the nerve to be pressurized and
irritation accompanied with pain and numbness will be felt in the
fingers (specifically, the thumb, the index, the middle and half of
the ring finger)... 
