How medicines can affect pregnancy

How medicines affect you and your baby depends on several factors. These include:

• How far along your pregnancy is.
• The strength and dose of the medicine.
• How easily the medicine can pass through the placenta.
• Genetic factors that affect your body's response to the medicine.
• Your overall health.

The way a medicine impacts a pregnancy depends on the medicine itself. There are several ways medicines can affect the fetus, including:

• No effect. Many medicines don't have any impact on pregnancy.
• Direct impact. Some medicines affect the fetus directly, causing damage, birth defects or death.
• Indirect impact. Some medicines indirectly affect the fetus. For example, some medicines lower the parent's blood pressure, which can reduce blood flow to the placenta.
• Altering the function of the placenta. Some medicines affect how the placenta functions. This can lead to reduced oxygen and nutrient supply to the fetus and cause an underweight or underdeveloped baby.
• Causing muscle contractions of the uterus. Some medicines cause muscles in the uterus to contract forcefully. These contractions can harm the fetus or trigger preterm birth.

Some medicines can stay in the body after you stop taking them and may cause birth defects. Ask your healthcare professional how long any medicines you take will stay in your body.