Objective: To investigate the impact of dietary and underlying factors on the iron status of women in early pregnancy and to provide evidence for preventing iron deficiency and iron deficiency anemia, thereby reducing the incidence of associated adverse outcomes. Methods: From November to December 2018, women in the first trimester of pregnancy (< 12 weeks gestation) who established prenatal records at the Shunyi District Maternal and Child Health Hospital, Beijing, were enrolled in this study, in which 388 participants were accessed for data including demographic characteristics, anthropometric measurements, parity, biomarkers reflecting iron status, and food-frequency questionnaire. SPSS 26.0 were used for statistical analysis. Dietary patterns were extracted using principal component analysis, and factor scores of each dietary pattern were calculated. Two-sided Fisher exact probability test and one-way ANOVA were conducted to access differences in iron status among the groups, and the differences were significant if P < 0.05. Iron deficiency was defined as serum ferritin(SF) < 30 μg/L. To analyze the potential role of dietary factors on iron deficiency during the first trimester, the collected data listed above were adopted as independent factors for the cross-sectional Logistic regression. We used Logistic regression to analyze the potential effects of baseline characteristics and dietary factors on iron status. Results: Among the 388 participants included in the analysis, 121 (32.2%) were iron deficient, in which 107 (27.6%) were iron depletion (ID), 8 (2.1%) were iron deficiency erythropoiesis (IDA), 6(1.5%) were iron deficiency anemia. The mean SF concentration was (50.4±35.3) μg/L. Multiparity(OR=3.9, 95%CI: 1.81-8.42, P=0.001)was a risk factor for iron deficiency during early pregnancy. No significant iron status differences were found among the participants with different educational levels and anthropometric measurements. In contrast, age (OR =0.96, 95%CI: 0.94-0.97, P < 0.001) was a protective factor. For multiparas, taking iron-containing supplements might have a protective effect for iron deficiency (OR=0.27, 95%CI: 0.09-0.83, P=0.022). The balance-diet pattern (OR=0.81, 95%CI: 0.66-1.00, P=0.054) only showed a marginally significant effect. Conclusion: Increasing attention should be paid to the iron status of pregnant multiparas and young pregnant women. For those women of reproductive age with the risk factors listed above, especially for multiparas, iron-containing supplements should be recommended to prevent gestational iron deficiency. The effect of the "balance" dietary pattern on iron status in the first trimester and following requires further research and discussion.