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Iron Status During Early and Late Pregnancy in a Swedish Multiethnic Population
Therese Karlsson1,2, Mathilda Forsby1, Anna Hagman3
1Department of Internal Medicine and Clinical Nutrition Institute of Medicine Sahlgrenska Academy University of Gothenburg Gothenburg Sweden gu.se.
Introduction:
While ethnic differences in maternal iron deficiency (ID) have been documented in other high-resource settings, such differences in Sweden remain unknown. This study assessed iron status and the prevalence of ID and anemia in pregnant women from different countries of birth in Sweden.
Material And Methods:
This secondary analysis included women enrolled in the randomized controlled Pregnancy and Vitamin D Intervention study (2020-2024;). Blood samples were collected in Trimesters 1 (T1) and 3 (T3), and additional data were obtained from questionnaires and medical records. Women were categorized by region of birth: Europe, Asia, and Africa. Anemia was defined as hemoglobin (Hb) < 110 g/L, and ID was defined using two serum ferritin (SF) thresholds: < 15 and < 30 μg/L.
Results:
A total of 128 women (median age 29.8 years) were included in TI, and 89 had blood samples at both T1 and T3. In those with data in both T1 and T3 (n = 89), median SF, serum iron, and Hb were significantly lower in T3 compared with T1 (all p < 0.001). Between T1 and T3, the prevalence of ID increased from 15% to 39% using SF < 15 μg/L and from 53% to 83% using SF < 30 μg/L (both p < 0.001). Anemia prevalence increased from 6% in T1 to 23% in T3 (p < 0.001). In T1, women (n = 128) from Asia and Africa more often had transferrin receptor concentrations > 4.4 mg/L than women from Europe (p = 0.02) but tended only to have a higher prevalence of SF < 15 μg/L (14% and 18% vs. 4%, p = 0.06). Self-reported use of iron supplementation (n = 89) increased from early to late pregnancy. According to medical records, 16% of women had been prescribed iron supplements during gestational weeks 6-12 and 85% by Week 32.
Conclusions:
ID was common and increased throughout pregnancy in this population in a high-resource country. No statistically significant differences were observed by region of birth. Despite prescribed iron supplements, nearly one-quarter were anemic in late pregnancy. This may reflect timing of treatment initiation, adherence, supplement dose, iron absorption, or other unknown contributors, highlighting the need to optimize iron status management during pregnancy. Trial Registration: ClinicalTrials.gov identifier: NCT05329428.