The role of nicotine in these instances is unclear. Much more is known about the dangerous effects of smoking on the foetus. It is believed that the presence of nicotine in the body while pregnant can lower a baby's birth weight. Nicotine has also been observed to cause an increased heart rate in pregnant women as well as a decrease in foetal breathing movements, depending on the nicotine intake. There have been a few reports of spontaneous abortion occurring during NRT and the possible role of nicotine in these instances cannot be dismissed out-of-hand. In rare cases miscarriages have been reported. The causal role of nicotine, however, has not yet been ascertained.You should not undertake a course of NRT if you are pregnant or intend on becoming pregnant during the course of the programme. In a specific case it is possible, however, that after a detailed consultation with you doctor, they may suggest that you engage in NRT. This is more likely if you have proven unable to give up smoking while pregnant and this is considered a greater danger to the foetus than NRT.