BackgroundIn women of childbearing age, a low dietary supply of iron, calcium, and magnesium is often observed. Minerals deficiency in pregnant women is often associated with abnormal body weight and may impact fetal development disorders. The aim of this study is to determine the relationship between prepregnancy body mass index (BMI) and the dietary intake of iron, calcium and magnesium and their concentrations in serum and hair in pregnant women. MethodThe study involved 97 Caucasian/white low-risk pregnant women at 12 weeks of gestation. The analysis of minerals in serum and hair samples was performed using atomic absorption spectrometry. Pre-pregnancy BMI was calculated based on self-reported weight. The study used a validated questionnaire and a 24-h recall nutrition interview, which were analyzed using Aliant software. ResultsIt was found that overweight and obese women exhibited higher magnesium concentration in serum, while iron content in serum and hair was markedly lower compared to women with normal body weight. The average total supply of iron was below the recommendation in pregnant women. Moreover, an inverse significant relationship was observed between BMI and iron concentration in hair and serum in the whole population. ConclusionIn conclusion, being overweight or obese before pregnancy is associated with low dietary iron intake and low iron concentration in serum and hair during the first trimester of pregnancy in women.