The prevalence of anaemia classified as Hb < 130 g/L versus the WHO classification of Hb < 110 g/L from all causes was 57.4% versus 6.1% at first hospital appointment, 94% versus 26.1% in third trimester, and 66.0% versus 12.2% preoperatively. Here, GSTM1 is linked to anemia (phenotype).