Effects on the unborn child
When a pregnant woman breathes in secondhand smoke, chemicals from the smoke can pass through her lungs into the bloodstream. Nicotine, carbon monoxide and other chemicals can cross the placenta affecting her unborn child. Women exposed to secondhand smoke are more likely to have a baby with a low birthweight of less than 2,500g. Overall, babies who are born to mothers exposed to SHS have a slightly lower birthweight than they would otherwise. This would not necessarily adversely affect a healthy baby, but could further compromise a baby with other problems.
The baby of a mother exposed to SHS may also be more likely to have preterm birth, meaning they are carried for less than 37 weeks.
Health effects on infants and children
Children are especially vulnerable to secondhand smoke. It is estimated that 23 Australian children under the age of fifteen died from illnesses related to secondhand smoke in 1998. In households where at least one parent smokes, the best way to protect children from secondhand smoke is by parents ensuring a total ban on smoking inside the home and car.
Infants exposed to secondhand smoke have a greater risk for SIDS (Sudden Infant Death Syndrome or cot death). SIDS researchers have recommended that mothers who smoke should not share a bed with their babies aged under four months old.
The children of parents who smoke have higher rates of lung or airways infections such as bronchitis, bronchiolitis and pneumonia during their first two years of life compared to children of nonsmokers. They are also more likely to develop wheeze illnesses. Children in this age group exposed to secondhand smoke have higher rates of admission to hospital.
Children of smokers are more likely to contract 'glue ear' (otitis media), which is an infection and swelling of the ear common in young children. Children of smokers are more likely to have 'glue ear' multiple times and to have long-term middle ear effusion (leaking of fluid). Middle ear disease is a common cause of hearing loss in children, which can delay speech development.
Children of smokers have a small lowering in lung function, meaning that on average, they cannot breathe in as deeply or breathe out as hard compared to children of nonsmokers. Children of all ages are affected, including adolescents, and some evidence suggests that reduced lung function may even persist into adulthood.
School-aged children of smokers are more likely to have symptoms such as cough, phlegm, wheeze, and breathlessness. Asthma is more common among children of smokers. Children with asthma exposed to secondhand smoke have a greater risk of developing symptoms earlier in life, and having more symptoms and asthma attacks. They are more likely to use asthma medications more often and for a longer period.
Secondhand smoke appears to impair the immune system in both children and adult nonsmokers, which increases their risk of infection. Children exposed to secondhand smoke are more likely to have lung complications during and after surgery involving a general anaesthetic. Children of smokers have an increased risk of meningococcal disease, which can sometimes cause death, mental disability, hearing loss, or loss of a limb. Smokers are more likely to be carriers of the bacteria that causes this disease.
Some evidence suggests that when a pregnant mother and a child is exposed to secondhand smoke before and after birth, her child may have an increased risk for certain childhood cancers, such as leukemias, lymphomas and brain cancer. More research is needed before this can be confirmed.
Effects of secondhand smoke that can lead to heart disease may begin in childhood and adolescence.
Even though some symptoms from SHS become less common with age, it is still important to protect children of all ages from secondhand smoke.