Effects of Maternal Vitamin D Levels on Prematurity: Feasibility Study in a Multicenter Observational Pilot

Background: Numerous studies have shown that hypovitaminosis D is linked to adverse maternal and infant health outcomes, such as intrauterine growth restriction, preeclampsia, cholestasis, hypertension, and gestational diabetes, all of which are potential causes of prematurity. Recognizing the significance of this issue and its impact on maternal–infant health, the VitDTracking research project was designed and registered on 4 March 2024, in the ClinicalTrials.gov database (Identifier: NCT06292195). The project includes a large-scale multicenter observational study, targeting a minimum initial sample size of 1800 participants. This paper describes the pilot study aimed at assessing the feasibility of the full-scale study. Methods: A multicenter observational pilot study was conducted in public health organizations in the Alentejo region, adhering to the research protocol. Data collection included 67 parameters: 37 obtained from a questionnaire and 30 from clinical records, with particular focus on maternal 25(OH)D levels and maternal–infant health outcomes. Feasibility was assessed through predefined outcome indicators and success criteria. Results: The pilot study enrolled 30 pregnant women and successfully met all feasibility criteria. The global recruitment rate was 73.17%, with an eligible recruitment rate of 88.2%. The refusal rate was low (11%), and adherence, retention, and completion rates were all 100%, indicating strong participant engagement. The questionnaire comprehension rate was 86.6%. Participating centers demonstrated the capacity to implement the study, adhering to the protocol with a compliance rate exceeding 90%. The study also highlighted a concerning prevalence of hypovitaminosis D and identified cases of premature birth and miscarriage. Conclusions: The pilot study confirmed the feasibility of recruitment methodologies and procedures, supporting the implementation of the large-scale observational study. The planned study will recruit approximately 1800 pregnant women to achieve an eligible cohort of 1000 samples, and a statistically significant final sample of 100 cases meeting the prematurity criterion.