Is it dangerous to have mice?

hiya. i have got mice problems they are doing building work at the end of the street and the mice has escaped into the houses i got an exterminator to lay down poisen and i think that has killed one the smell is so bad and worst of all its died somewere between the toilet which hasnt even got a window i have got a seven month old daughter and just found out i am pregnant :) but i hve still got mice and a stench of the dead one is the smell harmfull to my baby and my pregnancy thankyou verry much for answerng