Smoking
Nicotine, tar, and carbon monoxide are chemical substances associated with smoking. If you smoke before or after your baby is born, you risk your health and your baby's. The sooner you quit, the better it will be for your baby.

It is a good idea to encourage your partner and other family members to quit too, because smoke from other people's cigarettes can put you and your baby at risk.

Caffeine and alcohol
Coffee, tea, cola and some other soft drinks, chocolate, and some nonprescription drugs contain caffeine. Caffeine travels into the blood of the baby but it does not appear to cause birth defects. However, you should limit the amount of caffeine you consume, because very high amounts of caffeine may contribute to some complications of pregnancy.

When you drink alcohol, it quickly goes through your bloodstream to your baby's bloodstream. It is best not to drink alcohol at all while you are pregnant. If you choose to consume alcohol, limit it to an occasional drink. Don't drink every day, and don't drink a lot in a short time.

Drugs
Many types of drugs can affect your baby, and some can cause severe birth defects or other problems for the baby.

Be sure your physician or health advisor knows about any drugs you were taking before your pregnancy. Also, you should not take any drugs—prescription or nonprescription—without the advice of a health care professional.