Smoking contributes to infertility and decreases the chance of conception whether you are a man or woman. Men who smoke are found to have a reduced total sperm count in addition to a decrease in the sperm's ability to fertilize an egg. Smoking diminishes the capacity of an ovary to create eggs that are capable of healthy fertilization. If you are pregnant and a smoker, you increase the risk of a low-birth-weight or preterm baby. An estimated 20 to 30 percent of low-birth-weight babies and 14 percent of preterm births are attributed to smoking in pregnancy, according the U.S. Surgeon General’s report on women and smoking. There is a higher chance your baby will have asthma if you smoked during pregnancy. Even some full-term babies will have diminished lung function if you smoked while pregnant.