Drugs used in obstetrics merit special mention because they have their effects on two patients rather than one. This chapter provides an understanding of the drugs commonly used by obstetricians, including drugs to increase uterine contractions, ergometrine, prostaglandins, tocolytics, atosiban, nifedipine, and beta2-adrenergic agonists. Oxytocin is a nonapeptide used to induce and augment labour and also to minimise post-delivery blood loss. The main use of tocolytics is to stop premature labour. They have also been used to facilitate delivery during Caesarean section by uterine relaxation and to treat uterine hyperstimulation, preventing fetal distress. Antihypertensive agents are widely used during pregnancy but they all cross the placenta and the available evidence does not always suggest that they are of benefit. Increasing the number of antenatal exposure of steroids is associated with reduced cognitive function, an increase in behavioural disorders and reduced birth weight.