Cigarettes contain over two thousand five hundred different chemicals. One of these chemicals is nicotine.
Nicotine is the drug that makes people want more cigarettes. This drug can pass through the placenta to an unborn baby.
Nicotine affects blood vessels - the tubes that carry blood and oxygen through a person's body. Nicotine makes blood vessels smaller, so they carry less blood and oxygen to an unborn baby.
Another poison released by cigarette smoking is carbon monoxide. When a pregnant woman smokes, carbon monoxide enters her blood.
It takes the place of some of the oxygen in her blood. This means an unborn baby is not getting the oxygen she needs. 下载全新《每日英语听力》客户端，查看完整内容