GSTM1 and sickle cell disease: A study carried out in Natal, Rio Grande do Norte, based on 1,940 umbilical cord bloodsamples from newborns of three maternity hospitals in the city, identified 37 cases ofabnormal hemoglobin (prevalence of 1.9%), of which 29 (1.5%) had sickle cell trait(HbS), six (0.31%) had C trace (HbC), one (0.05%) had sickle cell anemia (HbSS) and one(0.05%) had Hb Bart's (suggesting alpha thalassemia trait).