Haematology of pregnancy

The physiological changes that occur during pregnancy, to meet the needs of the developing fetus, can lead to complications in vulnerable patients.Close proximity of fetal and maternal circulations enables effective transfer of nutrients and oxygen but passage of certain substances can also have disastrous consequences for mother or baby. For example, teratogenicity may arise from maternal drugs, and fetal antigenic material passing into the maternal circulation may cause maternal alloimmune sensitization syndromes. Iron deficiency and lack of other haematinics may result from increased demand. The massive increase in uterine blood flow and vascular compliance, necessary to maintain the blood supply for the developing fetus, can lead to significant haemorrhage at the time of placental separation. 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.