Fetal anaemia is a rare condition which can result from a failure of production of fetal red blood cells, accelerated haemolysis, or fetal bleeding. The three most common causes are red cell isoimmunisation, fetomaternal haemorrhage and Parvovirus B19 infection. There have been major advances in the diagnosis and management of fetal anaemia over recent decades. Having established successful techniques for intrauterine therapy, it is particularly important that cases amenable to treatment are not missed. Detection of at-risk cases has been enhanced by free fetal DNA technology. Middle Cerebral Artery Doppler has transformed the surveillance of affected pregnancies, avoiding the risks of invasive testing by amniocentesis.

Irrespective of the aetiology of potential fetal anaemia, the aim of surveillance of at-risk pregnancies is to predict anaemia before the onset of hydrops. Middle Cerebral Artery Peak Systolic Velocity (MCA-PSV) measured by ultrasound Doppler is currently recommended to be used as the primary technique to detect and monitor fetal anaemia. Pregnancies with a fetus at significant risk for fetal anaemia are to be delivered at 37-38 weeks of gestation unless indications develop prior to this time.