The production of physical defects in the FETUS by a drug or chemical agent, often one that would cause no harm to an adult. Whether and how the EMBRYO is affected depends on what stage of development it has reached when the drug is given. The age of early differentiation – that is, from the beginning of the third week to the end of the tenth week of pregnancy – is the time of greatest susceptibility. After this time the likelihood of CONGENITAL malformation resulting from drug treatment is much less.

Although the risks are nil or very small with most drugs, no medication should be given to a pregnant woman, particularly during the first few months of pregnancy, unless it is absolutely essential for her health or that of her unborn child. Alcohol is regarded as ‘medication’ in this context as it can lead to FETAL ALCOHOL SYNDROME.