First, u r gay will address drinking however both are extremely devastating:
"When a woman is pregnant, drinking is one of the most potentially harmful things she can do.
The reason? Fetal Alcohol Syndrome (FAS). Doctors tell us that FAS is one of the leading causes of birth defects and developmental disabilities in the United States." 
Now for the smoking, it looks to me like both are equally as bad:
"The nicotine in cigarettes can cause artery spasms. Because blood is sent to the placenta via these arteries, these spasms can reduce the amount of oxygen and nutrients that the baby receives. As a result of nutrient and oxygen deficiency, the child is more likely to have a low birth weight. In fact, women who smoke heavily are twice as likely to give birth to a baby weighing less than 5 ½ pounds. Additionally, smoking can also increase the risk of premature delivery, which can lead to health conditions such as mental retardation, cerebral palsy and even death. The good news, however, is that women who stop smoking by the end of their second trimester drastically reduce their risk of having a premature or low birth weight baby." 
Now the reference for both drinking and smoking mixed: "Cigarette smoke and alcohol can damage the health of unborn babies.
Smoking by pregnant women is associated with low birthweight and premature birth, as well as higher rates of illness (colds, bronchitis, ear infections, etc.), breathing problems, and sudden infant death syndrome (SIDS) in their babies. Birth defects of the heart, brain, and face are also more common among babies born to smokers. Children whose mothers smoked during pregnancy tend to be physically smaller than children of non-smokers, and may continue to have higher rates of respiratory illness, such as asthma, for many years." 
'BASICALLY IF YOU ARE PREGNANT DON'T SMOKE OR DRINK ALCOHOL IT IS NOT VERY WISE!'