Fetal anaemia

Abstract

Fetal anaemia is a relatively rare occurrence with varied aetiology. Although it may cause reduced fetal activity, or the development of hydrops, or be detected by chance on ultrasound scanning, it may also present with stillbirth or neonatal anaemia, with or without haemodynamic compromise. Broadly speaking, anaemia is caused by one, or a combination, of the following problems: (i) a failure of red cell production; (ii) accelerated red cell destruction; (iii) loss of red blood cells (bleeding). This is also the case for the fetus. Anaemia caused by an acute loss of blood will be accompanied by hypotension and shock, and a significant risk of sudden death, or critical neurological and visceral ischaemia. Conversely, the chronic development of anaemia in the fetus carries no risk of haemodynamic compromise, but will eventually lead to high output cardiac failure, hypoxia, metabolic acidosis and hydrops. The management of fetal anaemia will be determined by the underlying cause, the severity, and the gestation. A conservative ‘wait and see’ approach is suitable in select cases, whereas immediate delivery is mandated in others. Intrauterine transfusion is a highly successful treatment, but is not always considered appropriate, carries some degree of risk, and requires subspecialist skills.