The immune systems of pregnant women work less effectively than normal in order to prevent the body rejecting the foetus. One of the effects of this is that pregnant women are more susceptible to traveller’s diarrhoea. Furthermore the pathogens which cause the diarrhoea are not killed off in the stomach as it produces less acid. The working of the bowels also slows down during pregnancy which means the pathogens can live longer than normal. One of the main risks of traveller’s diarrhoea is dehydration, and this in turn reduces the blood flow to the placenta making the maternal blood more acidic. This can jeopardise the pregnancy and even lead to the death of the unborn child.