Well, the cigarette butt contains many different types of carcinogens and a carcinogen is a cancer causing agent. So it's a molecule that when reacts with molecules in the cells of our body, can basically lead to cancer and cancer cells. So when that individual smokes, they inhale all those different carcinogens and those carcinogens eventually end up in the blood of that individual. Now, the problem with that is, remember, the placenta is the organ that basically exchanges nutrients and gas products between the fetal blood and that placenta and that mother's blood. The problem with these carcinogens is they can easily cross across that placental membrane. And so all those carcinogens that end up in the blood can also end up within that developing fetus.