Smoking contains carcinogens which are the cancer causing agent and disturbs the respiratory system of the baby. What are the effects of smoking during pregnancy on expecting mom? The most expected health risk is of miscarriage. The chances of stillbirth are also high in such pregnant women. How smoking during pregnancy affects growth of the baby? It slows down the growth of the baby by halting the supply of oxygen and blood to the baby. The limited supply of nutrients through blood may lead to low birth weight of the baby as well. Placental abruption and low lying placenta are also some of the affects of smoking during pregnancy.