Is nicotine gum safe for pregnant women?

My freind is a heavy smoker that is trying to quit and just found out she is pregnant- she switched from the patch to the gum- part of me is still uneasy about this. But I have always wondered b/c I myself struggled quitting cold turkey when I found out- is it safe?

32+ wks pregnant w/ lil girl
22 month old son
My freind is about 6-7 wks along