Smoking has been associated with a number of pregnancy complications. One is an increased risk of ectopic pregnancy. In an ectopic pregnancy, the embryo becomes implanted in a fallopian tube or other abnormal site instead of the uterus. With the rarest of exceptions, these pregnancies do not result in the birth of a baby, and must be removed surgically or with drug treatment to protect a woman's life.
Cigarette smoking also appears to double a woman's risk of developing placental complications (which occur in about 1 percent of pregnancies). These include placenta previa, a condition in which the placenta is attached too low in the uterus and covers part or all of the cervix; and placental abruption, in which the placenta separates from the uterine wall before delivery. Both can result in a delivery that jeopardizes the life of mother and baby.
Smoking during pregnancy also increases the risk of stillbirth, miscarriage, and severe vaginal bleeding.