Because of great physiological changes during pregnancy, pregnant women can easily become a high-risk group with the lack or excess of trace elements, resulting in obstruction of normal body activities and abnormalities, especially in the second trimester, fetal function development will rapidly deplete maternal trace element reserves. Meanwhile, low-selenium regions are the high incidence areas of various endemic diseases. In this study, the contents levels of 12 trace elements (Al, Ca, Cd, Cu, Fe, Mg, Mn, Ni, Pb, Se, V and Zn) in hair samples, which were collected from 156 women of child-bearing age (non-pregnant and in the second trimester) living in the 5 townships in Ejin Horo Banner (Ordos City, Inner Mongolia), the influence factors and interaction between Se and other elements were studied by using the inductively coupled plasma-atomic emission spectrometry (ICP-AES) and atomic fluorescence spectrometry (AFS). The results showed that (1) there was a deficiency of Se in all the hair samples, which were related to the fact that the study area was located in China’s low-selenium region. In addition, 92%, 95%, 35% and 60% of women had an lack of Mn, Fe, Cu, and Mg, respectively. It was recommended to increase the production of Se-enriched foodstuff such as wheat, Brazil nuts, garlic, apples and persimmons, and the food of seafood, nuts, and lentils which were rich in Mn, Cu, Mg, and Fe. Whereas 80%, 52% and 34% of women had an excess of V, Cd and Pb, respectively. (2) The content levels of Al, Ca, Cd, Cu, Fe, Pb, V and Se in hair samples of the second trimester women were all lower than those in the non-pregnant group. This may be due to the fact that more nutrition is required for rapid growth and development of the fetus in the second trimester. (3) It is noteworthy that there were two significant positive correlations not only between Se content and age in non-pregnant women but also between Cu content and age in the second trimester. In addition, there was no significant correlation between Ca and Mg in all women in the study area, which may be related to a Ca/Mg ratio higher than 10. (4) We found that there was a significant correlation between Cd-Pb, Ni-Pb and Ni-Cd in the non-pregnant group and the second trimester group, indicating that Cd, Ni, and Pb might have the same source and there was a higher exposure risk in the study area.