You could cause birth defects and a low birth weight. You could also get lung cancer and die a miserable slow painful death for purposely hurting your unborn child.

Smoking and pregnancy Not only does tobacco seriously damage maternal health, it also affects the health of their babies. Women who smoke have more difficulty becoming pregnant than non-smokers. They are also more prone to spontaneous abortion. Babies born to smoking mothers have lower survival rates, and those who survive are more likely to be sickly. Exposure to smoke also increases the risk of respiratory diseases in babies and small children. When a pregnant woman smokes, her unborn child smokes with her. She passes carbon monoxide and nicotine to the bloodstream of the fetus, lessening the supply of oxygen and accelerating its heart beat. In addition, her newborn child is likely to be underweight by an average of 300 grams. Nicotine is transmitted in the milk of a lactating mother to her infant. The risk of developing bronchitis or pneumonia during the first year of life is doubled if the parents smoke. The risk of otitis (inflammation of the ear) is also increased in the children who live with smokers compared to those who do not. How does smoking affect the baby? a. Risk of spontaneous miscarriage in early pregnancy is 2 times higher compared to the non-smokers. This may result partly from an increased number of abnormal embryos, with which smoking is associated. b. Risk of preterm labour and prematurity of baby. c. Risk of birth defects. Most studies show a relatively higher risk for babies of smoking mothers. d. Increased risk of abruptio placentae. This is a serious condition where the placenta separates itself prematurely from the uterus before birth, causing abdominal pain and bleeding from the vagina. This condition can lead to danger and even death for both mother and child. e. Delayed physical and intellectual development in the child. f. Adverse effects on maternal health e.g. an increased risk of cancer; gut, heart and lung diseases. g. Possible risk for Sudden Infant Death Syndrome (SIDS). How does low birth weight affect the baby? Infants of smoking mothers weigh on average 300 grams less than those of non-smoking mothers. Low birth weight in babies is not due only to prematurity but also to intrauterine growth retardation (poor growth of the baby in the womb). A growth-retarded baby is one who is not growing well in the mother's womb because of the lack of nutrients and oxygen. Such a baby faces an increased risk of fetal death in the womb and may require an early or emergency delivery by induction or caesarean section. The baby also has a higher chance of dying in the early period after birth compared to a normal, healthy baby. Other problems which a growth-retarded or immature baby may suffer from include low blood sugar, low temperature and aspirating meconium in the womb or when it is born, and respiratory difficulties from immature lungs. How does smoking affect the baby's growth in the womb? Smoking reduces the transfer of oxygen and nutrients to the baby while it is in the womb. Low birth weight, one of the effects of smoking, may be due to the following: a. Nicotine found in tobacco smoke constricts and reduces the placental bed blood vessel flow. b. Carbon monoxide, also found in tobacco smoke, binds preferentially to fetal haemoglobin excluding oxygen. The higher level of carboxyhaemoglobin (a combination of carbon monoxide and haemoglobin) reduces oxygen supply to fetal tissues. c. The toxic effect of smoking damages the placenta villi and barrier (the attachment lining between the placenta and the womb), thus reducing the transfer of amino acids and other nutrients to the fetus. Source: http://www.kkh.com.sg/PatientHealthLibrary/WomensHealth/Pregnancy/smoking.htm