Haematology of pregnancy

Physiological changes which occur during pregnancy are generally of benefit to mother and fetus but may also cause problems peculiar to that state. The close proximity of fetal and maternal circulations enables effective transfer of nutrients and oxygen but teratogenicity may arise from maternal drug treatment and fetal antigenic material passing into the maternal circulation may cause maternal alloimmune sensitisation syndromes. Iron deficiency and lack of other haematinics may result from increased demand. Haemorrhage at the time of placental separation may be substantial due to the massive increase in uterine blood flow and vascular compliance necessary to maintain the blood supply for the developing fetus. Changes in coagulation factors help to combat this risk but increase the potential for systemic thromboembolic events. Women with pre-existing haematological disease may be at particular risk during pregnancy or the pregnancy may be compromised by the underlying state. Whilst the majority of pregnancies progress without complication, management of high risk cases should be coordinated in joint obstetric haematology clinics.