Altered sex hormone regulation in women with obesity can lead to subfertility, perinatal complications, as well as bodily changes secondary to hyperandrogenism.4 5 Effects of obesity on fertility are irregular periods, reduced number of viable egg cells and disrupted implantation.6 Pregnant women with obesity are at increased risk of miscarriage, gestational diabetes and pre-eclampsia as well as large for gestational age babies, congenital defects and birth complications such as haemorrhage.7 The gene discussed is PLXNA3; the disease is obesity due to melanocortin 4 receptor deficiency.