Why would a pregnant woman not be able to eat soft cheeses?
Everybody has different rules for what pregnant women should and should not eat, and you definitely should clarify with the individual.  

Usually the concern with cheese is over bacteria.  The typical rule about cheese is to avoid softer, raw milk cheeses for fear of listeria, which can affect the baby.

There is more information here: http://americanpregnancy.org/pregnancycomplications/listeria.html