I am pregnant with twins for the 3rd time and YES they do often recommend this FOR A PERIOD OF TIME. To quit cold turkey during a high risk pregnancy can cause stress to the fetus(s) causing a miscarriage. With my first set of twins I smoked prior and they put me on a strict schedule to quit even though it made me sick to even think about smoking. I would have quit cold turkey had the doctors let me. HOWEVER... I have never heard of them being ok with it thru the entire pregnancy. I've also never heard of them recommending it for a normal-risk pregnancy but I've had high risk all 3 times due to multiples so I have no experience with that I guess.