These include maternal anaemia (Hb <11 g/dl)(82), particularly in the first trimester(83) and when severe (Hb <7 g/dl)(84), gestational diabetes mellitus (GDM)(84), maternal overweight (BMI 25·0–29·9)(11,85) and obesity (BMI ≥ 30)(11,12,85), antenatal depression(86) and chronic hypertension (pre-existing or hypertension diagnosed before 20 weeks)(11,85) (see also online Supplementary Table S3). Here, GSTM1 is linked to gestational diabetes.