Use of Vitamins and Supplements During Pregnancy and Their Association with Maternal and Birth Outcomes: A Prospective Cohort Study.

Background: Previous research shows that sufficient maternal nutrition is essential for good maternal and fetal outcomes; however, maternal use of prenatal supplements might vary. Objective: The study tracks the type and the patterns of maternal supplement use in a Jordanian cohort, evaluating rates of adherence through pregnancy and exploring maternal and birth outcomes. Methodology: A prospective cohort study was conducted from February 2023 until March 2025 with 199 pregnant women enrolled through convenience sampling from the second trimester up to delivery, at Gynecologic and Pediatric Mafraq Government Hospital, Jordan. Assessment was done through structured interviews and medical record reviews at baseline, at monthly antenatal visits, and a clinical assessment at month seven of gestation. Information collected included sociodemographic data, medical and obstetric history, details of supplement use, maternal and neonatal outcomes. Results: Among the participants, the most used supplements were folic acid (82.9%) and iron (71.9%). Overall adherence to supplements was 63.8% with fluctuations across trimesters of pregnancy. Seven significant univariate associations were identified: low birth weight with multivitamin non-use, urinary tract infection (UTI) with calcium use, gestational hypertension with non-use of magnesium, iron, folic acid, and omega-3, and cesarean delivery with non-use of calcium and vitamin D (p<0.05). Only iron and magnesium were shown to be significantly associated with gestational hypertension (adjusted p=0.019) following Benjamini-Hochberg FDR adjustment for multiple comparisons; the other associations are considered exploratory. Following multivariable adjustment for covariates, calcium continued to be associated with increased odds of UTI (aOR=2.70) and decreased odds of cesarean birth (aOR=0.52), whereas iron and omega-3 continued to be associated with lower odds of gestational hypertension (aOR=0.13 and 0.09, respectively). Conclusion: Appropriate use of vitamins and supplements during pregnancy appears important, as insufficient intake of some supplements was associated with negative pregnancy and neonatal outcomes. Despite that the study findings do not establish causality; they support the importance of promoting proper supplement intake and adherence during pregnancy to prevent deficiency-related outcomes. Further studies are needed to confirm these associations.