Abstract

introduction: Vitamin D 25(OH)D deficiency is common in Latin America (52% in Chile).The Chilean state has been fortifying milk and flour with vitamin D3 starting in July 2024. objective: To evaluate 25(OH)D deficiency in pregnant women at childbirth and to identify associated risk factors. Material and methods: Cross-sectional study in 84 women from 2018 to 2019. Blood levels of 25(OH)D were measured at delivery. Data were collected on sociodemographic variables, health, and exposure to sunlight. Data were analyzed to identify frequency of 25(OH)D deficiency and risk factors. Results: The median age was 26.5 years, with 41.7% of first-time births and 83% of vaginal delivery. Sixty-three percent were overweight/obese at birth; 70.2%had plasma levels of 25(OH)D ? 12 ng/dl (severe deficit),the median level of 25(OH)D was 8.9 ng/ml (IQR: 6.5-13.3 ng/ml). The risk factors found were gestational diabetes (aOR: 7.03; 95%CI: 1.3-37.9) and weight gain in pregnancy over p75 (aOR: 4.29; 95% CI: 1.02-17.9). Working outdoors was found to be a protective factor (aOR: 0.14; 95%CI: 0.03-0.65). Conclusions: In Puerto Montt, 70.2% of pregnant women had a severe deficit of 25(OH)D at delivery. The deficit was associated with gestational diabetes and excessive weight gain during pregnancy. Outdoor maternal work reduces risk. © 2025 Sociedad Chilena de Obstetricia y Ginecologia. All rights reserved.