My sis 24 yrs, pregnant by 2 months, has chicken pox, docs asking to abort, is it needed?how serious is it?pls guide

Difficult issue: About 2% of those infants born to mothers with chickenpox during the first 20 wks of pregnancy will have the fetal varicella syndrome.The risk may be higher in the earlier weeks. The effects include mental deficiency with or without seizures, brain shrinkage, small heads, eye defects, limb and skin defects. This is a difficult position to be in for anyone, but these are the current facts.