Steroid sulphatase deficiency is a recently recognised genetically determined inborn error of metabolism. Originally identified as an enzyme disorder of the placenta (commonly termed placental sulphatase deficiency), it is now known that the progeny of affected pregnancies have a generalised steroid sulphatase deficiency and that the enzyme defect persists throughout life. The disorder is characterised clinically by markedly low maternal oestrogen excretion in the presence of normal fetal growth and development. The importance of antenatal diagnosis lies in the differentiation of this disorder from the more ominous fetal defects that result in low oestrogen concentrations. This paper summarises the relevant literature and describes a case in which biochemical tests were used for the antenatal diagnosis of steroid sulphatase deficiency. The pregnancy resulted in a healthy baby boy delivered vaginally after a spontaneous labour.