Non-narcotic analgesics. Use in pregnancy and fetal and perinatal effects.

Aspirin and related non-narcotic analgesics such as paracetamol (acetaminophen) are present in almost every 'Western' household and are so commonly used that the public often does not think of them as drugs. Although the toxic effects of overdoses are well recognised by the medical and related professions, the potential adverse effects of repetitive dosing, within the commonly recommended therapeutic range, are not. This is particularly true during pregnancy, where the relative overall general safety of the agents is overshadowed by the possible subtle but potentially pervasive effects on the fetus. Marketing publicity, particularly about recently introduced related agents, has at times failed to take into account these less obvious, but nevertheless potentially lethal, side effects. It is now likely that aspirin and/or paracetamol are used during pregnancy by most women and that the earlier figures are underestimates. Although animal studies have shown significant effects of non-steroidal anti-inflammatory agents (NSAIDs) on the fetal circulation, particularly on the developing pulmonary circulation, the data on human pregnancy are less convincing. Nevertheless, the possible association of these drugs with prolonged gestation, and an increased incidence of the syndrome of persistent pulmonary hypertension of the newborn and of intracranial haemorrhage, demand that prudence be exercised when using these drugs during pregnancy. At the very least, more conclusive evidence is necessary that fetal and neonatal complications are not increased.