The reduction in drug use in pregnancy is probably driven by the continued attention in the news media to drug-induced fetal abnormality. Another important feature is that with the increasing age at which women elect to have children, more women are already on long-term medication for chronic conditions at the time they embark on pregnancy. Medication taken in pregnancy can harm the unborn child through teratogenic effects. Teratogenesis is defined as dysgenesis of fetal organs, either in terms of structural integrity or function. Pharmacokinetics refers to the absorption, distribution, metabolism and excretion of a drug; variables that can be influenced by maternal physiological adaptation to pregnancy. Gastrointestinal transit time is prolonged due to slower emptying of the stomach and reduced gut motility, hence the rationale of parenteral administration of drugs in labor. In pregnancy, renal plasma flow, glomerular filtration rate and creatinine clearance all increase, which in turn leads to more rapid elimination of water soluble drugs, such as Lithium and ampicillin, which are excreted unchanged. In terms of breastfeeding, chloroamphenicol is best avoided in breastfeeding due to the risk of grey baby syndrome, while tetracyclines should also be avoided due to the risks of dental discoloration. Calcium channel blockers effectively control antenatal and postnatal hypertension. Paracetamol is safe in pregnancy and lactation. Neuroleptics are unlikely to be prescribed in pregnancy, but women on long-term treatment or prophylaxis for functional psychosis may present with pregnancy. In the management of depression, tricyclic antidepressants appear to be the drugs of choice along with fluoxetine as an alternative. Alternatives to lithium in the treatment of mania or bipolar affective disorder in pregnancy are chlorpromazine and haloperidol. Fetal malformations associated with teratogens affect the CNS, cardiovascular system, arms and legs, orofacial clefting and multisystem defects.