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AQA GCSE Biology · 8461
AQA 8461 · 4.2.2.6 Lifestyle and Disease Check the specification (PDF) (opens in a new tab)
Discuss the human and financial costs of non-communicable diseases locally and globally.
Explain the effect of lifestyle factors (diet, alcohol, smoking) on disease incidence.
Identify risk factors and causal mechanisms for cardiovascular disease, diabetes, liver/brain function, and lung disease/cancer.
Explain the effects of smoking and alcohol on unborn babies.
Understand the principles of sampling in epidemiological data.
A developing foetus needs oxygen and nutrients but cannot obtain them independently. The placenta, attached to the wall of the uterus and connected to the foetus by the umbilical cord, allows useful substances to pass from the pregnant person's blood towards the foetus. Waste substances such as carbon dioxide pass in the opposite direction.
The two blood supplies do not normally mix directly. Substances cross between them through the placenta. However, the placenta is not a perfect barrier: alcohol, carbon monoxide and other harmful chemicals from cigarette smoke can also cross it. The lifestyle of a pregnant person can therefore affect the environment in which the foetus develops.
Maternal and foetal blood do not mix directly, but substances cross the placental tissue: oxygen, nutrients and some harmful chemicals pass towards foetal blood, while carbon dioxide passes towards maternal blood.
When tobacco smoke is inhaled, carbon monoxide and other harmful chemicals travel from the lungs into the bloodstream. They can then cross the placenta and enter the foetus's body.
Carbon monoxide causes the foetus to struggle to obtain enough oxygen. Oxygen is needed for aerobic respiration, which releases energy for cell processes. A reduced oxygen supply can therefore restrict normal growth and development. Smoking during pregnancy is associated with an increased risk of outcomes including miscarriage, premature birth and low birth weight. Breathing in second-hand smoke can also expose a pregnant person and the foetus to harmful chemicals.
This is a chain of cause and effect:
cigarette smoke inhaled → harmful chemicals enter maternal blood → chemicals cross the placenta → less oxygen is available to the foetus → growth and development may be impaired
Alcohol enters the pregnant person's bloodstream after it is absorbed from the digestive system. It can cross the placenta, so the developing foetus is exposed to alcohol as well. The foetus cannot process alcohol as effectively as an adult, making its developing cells and organs particularly vulnerable.
Alcohol can interfere with development of the brain, spinal cord and other parts of the body. Drinking during pregnancy, especially during the first three months, increases the risk of miscarriage, premature birth and low birth weight.
Exposure to alcohol before birth can also cause foetal alcohol spectrum disorder (FASD). Its effects may last throughout life and can include poor growth, characteristic facial abnormalities, learning difficulties and behavioural problems. The type and severity of harm can vary, so an individual outcome cannot be predicted simply from knowing that exposure occurred.
Smoking and alcohol are risk factors: exposure increases the probability of harmful outcomes, but it does not guarantee that every pregnancy will be affected in the same way. The effect can depend on factors such as the amount and timing of exposure, as well as other biological and environmental influences.
Nevertheless, there are clear biological mechanisms connecting these substances with harm. Cigarette smoke can reduce the foetus's oxygen supply, while alcohol can disrupt the development of the brain and other body structures. For this reason, NHS guidance advises avoiding smoking and alcohol during pregnancy.
The placenta allows exchange between maternal and foetal blood supplies, but it is not a complete barrier. Harmful substances can cross it even though the two blood supplies do not normally mix directly.
Smoke inhaled → carbon monoxide and other toxins enter the blood → cross the placenta → foetus receives insufficient oxygen → impaired growth and development.
Risks include miscarriage, premature birth and low birth weight. Second-hand smoke can also cause exposure.
Alcohol enters maternal blood → crosses the placenta → is processed poorly by the foetus → developing organs may be damaged.
Risks include miscarriage, premature birth, low birth weight and FASD. FASD can cause lifelong problems with growth, facial development, learning and behaviour.
Smoking mainly harms development by exposing the foetus to toxic chemicals and reducing its oxygen supply. Alcohol can directly disrupt the development of the brain and other body parts. Both increase risk rather than determining one certain outcome.
Link each substance to a route and an effect: it enters the pregnant person's blood, crosses the placenta and interferes with foetal development.
For smoking, make the oxygen link explicit: carbon monoxide reaches the foetus, so it receives less oxygen for growth and development.
Do not write that the placenta blocks all harmful substances or that maternal and foetal blood mix directly.
Use risk language accurately: smoking or drinking alcohol increases the chance of harmful outcomes; it does not mean that every exposed pregnancy will have the same outcome.
Keep the two mechanisms distinct: cigarette smoke reduces the foetus's oxygen supply, whereas alcohol can directly disrupt the development of the brain and other body parts.
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Last updated
Placenta
A temporary organ attached to the wall of the uterus where substances are exchanged between the pregnant person's blood and the developing foetus.
Foetus
The stage of human development from about eight weeks after fertilisation until birth.
Carbon monoxide
A poisonous gas in cigarette smoke that can pass through the placenta and reduce the oxygen available to the foetus.
Foetal alcohol spectrum disorder (FASD)
A range of lifelong physical, learning and behavioural difficulties caused by exposure to alcohol before birth.
Miscarriage
The loss of a pregnancy before the baby is able to survive independently.
Premature birth
Birth before the pregnancy has reached its usual full length.
Put your knowledge into practice — try past paper questions for Biology
Placenta
A temporary organ attached to the wall of the uterus where substances are exchanged between the pregnant person's blood and the developing foetus.
Foetus
The stage of human development from about eight weeks after fertilisation until birth.
Carbon monoxide
A poisonous gas in cigarette smoke that can pass through the placenta and reduce the oxygen available to the foetus.
Foetal alcohol spectrum disorder (FASD)
A range of lifelong physical, learning and behavioural difficulties caused by exposure to alcohol before birth.
Miscarriage
The loss of a pregnancy before the baby is able to survive independently.
Premature birth
Birth before the pregnancy has reached its usual full length.