Apart from low Hb, also elevated Hb levels are associated with adverse perinatal outcome.4,15–17 As a result of poor plasma expansion, blood viscosity increases, leading to a reduction in blood flow and fetomaternal exchange of oxygen and nutrients in the placenta.15,16 High Hb concentrations are associated with pregnancy-induced hypertension and preeclampsia.15–17. The gene discussed is GSTM1; the disease is preeclampsia.