Objective: The coexistence of underweight (UW) and overweight (OW)/obese (OB) at the population level is known to affect iron-deficiency anemia (IDA), but how the weight status affects erythropoiesis during pregnancy is less clear at a population scale. This study investigated associations between the pre-pregnancy body mass index (pBMI) and erythropoiesis-related nutritional deficiencies. Design: Anthropometry, blood biochemistry, and 24-h dietary recall data were collected during prenatal care visits. The weight status was defined based on the pBMI. Mild nutrition deficiency-related erythropoiesis was defined if individuals had an ID, folate depletion, or a vitamin B12 deficiency. Setting: The Nationwide Nutrition and Health Survey in Taiwan (Pregnant NAHSIT 2017-2019). Participants: We included 1456 women aged 20 to 45 years with singleton pregnancies. Results: Among these pregnant women, 9.6% were UW, and 29.2% were either OW (15.8%) or OB (13.4%). A U-shaped association between the pBMI and IDA was observed, with decreased odds (OR; 95% CI) for OW subjects (0.6; 0.40.9) but increased odds for UW (1.2; 0.82.0) and OB subjects (1.2; 0.81.8). The pBMI was positively correlated with the prevalence of a mild nutritional deficiency. Compared to normal weight (NW), OB pregnant women had 3.4-fold (3.4; 1.48.1) higher odds for multiple mild nutritional deficiencies, while UW individuals had lowest odds (0.3; 0.1-1.2). A dietary analysis showed negative relationships of pBMI with energy, carbohydrates, protein, iron, and folate intakes, but positive relationship with fat intakes. Conclusion: The pre-pregnancy weight status can possibly serve as a good nutritional screening tool for preventing IDA during pregnancy.
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