The two main objectives of this study were: (i) to estimate the prevalence of anemia at the end of pregnancy among women followed-up in a reference maternity unit in France and (ii) to identify what were the clinical factors and biomarkers at the first trimester of pregnancy (including Hb, mean corpuscular volume (MCV), SF, STfR, SF/STfR ratio and Hepc) that best predicted anemia at the end of pregnancy. The gene discussed is GSTM1; the disease is anemia (phenotype).