We also found a significantly higher risk of adverse outcomes such as preterm birth, very low birthweight and transfer to higher care or stillbirth for those with high Hb result, as has been found in other studies,[26, 27] possibly due to inadequate plasma volume expansion, or the impaired response to inflammation and infection,[5, 26] or possibly due to high Hb levels before pregnancy. This evidence concerns the gene GSTM1 and infection.