The effect of lifestyle on some non-communicable diseases: The effects of smoking and alcohol on unborn babies.

The idea

Substances in tobacco smoke and alcohol can cross the placenta from the mother's blood into the fetus. Smoking reduces the oxygen supply to the fetus because carbon monoxide binds to haemoglobin and nicotine narrows blood vessels, so the fetus may grow more slowly and have a lower birth mass. Alcohol crosses the placenta and can damage the developing brain and other organs, leading to fetal alcohol syndrome, which may cause learning difficulties, distinctive facial features and behavioural problems. Because the fetus cannot detoxify these substances as effectively as an adult, the effects can be severe and permanent. The risk generally increases with the amount consumed, so avoiding smoking and alcohol during pregnancy reduces the chance of harm. These effects are examples of how lifestyle factors can affect health, and the resulting conditions are non-communicable.

What earns the marks

• Carbon monoxide in tobacco smoke binds to haemoglobin, reducing the oxygen carried to the fetus and slowing growth.
• Nicotine narrows blood vessels in the placenta, reducing blood flow and the supply of oxygen and nutrients to the fetus.
• Smoking during pregnancy increases the risk of low birth mass and premature birth.
• Alcohol crosses the placenta and can damage the developing brain and organs, causing fetal alcohol syndrome.
• Fetal alcohol syndrome can lead to learning difficulties, behavioural problems and distinctive facial features.
• The fetus cannot break down alcohol or tobacco chemicals as effectively as an adult, so the effects may be permanent.

Common mistakes and how to put them right

• Thinking the placenta filters out all harmful substances.

  Put it right: Alcohol, nicotine and carbon monoxide can cross the placenta.

• Believing only heavy drinking is harmful.

  Put it right: Any alcohol during pregnancy carries risk, and the safest approach is to avoid it.

• Confusing low birth mass with prematurity.

  Put it right: Low birth mass is a measure of size, while premature birth means being born before the expected date.

Exam tips

• Name the specific substance and its effect, for example carbon monoxide reduces oxygen transport.
• Use the term placenta correctly when explaining how substances reach the fetus.
• Link lifestyle choices during pregnancy to the health of the unborn baby rather than giving vague advice.