When you are pregnant, you are not just "eating for two." You also breathe and drink for two. If you smoke, use alcohol or take illegal drugs, so does your unborn baby.
To protect your baby, you should avoid
Tobacco. Smoking during pregnancy passes nicotine, carbon monoxide, and other harmful chemicals to your baby. This could cause many problems for your unborn baby's development. It raises the risk of your baby being born too small, too early, or with birth defects. Smoking can also affect babies after they are born. Your baby would be more likely to develop diseases such as asthma and obesity. There is also a higher risk of dying from sudden infant death syndrome (SIDS).
Drinking alcohol. There is no known amount of alcohol that is safe for a woman to drink during pregnancy. If you drink alcohol when you are pregnant, your child could be born with lifelong fetal alcohol syndrome disorders (FASD). Children with FASD can have a mix of physical, behavioral, and learning problems.
Illegal drugs. Using illegal drugs such as cocaine and methamphetamines may cause underweight babies, birth defects, or withdrawal symptoms after birth.
Misusing prescription drugs. If you are taking prescription medicines, carefully follow your health care provider's instructions. It can be dangerous to take more medicines than you are supposed to, use them to get high, or take someone else's medicines. For example, misusing opioids can cause birth defects, withdrawal in the baby, or even loss of the baby.
If you are pregnant and you are doing any of these things, get help. Your healthcare provider can recommend programs to help you quit. You and your baby's health depend on it.
Dept. of Health and Human Services Office on Women's Health