Medication, Vaccine, and Folic Acid Use Among Pregnant Women in Belgium: Insights from the BELpREG Cohort

BackgroundSafety data for most medications in pregnancy remain limited, yet pharmacological treatment is often necessary. Evidence on real-world medication use in pregnancy including over-the-counter products and folic acid is scarce, especially in Belgium. MethodsWe conducted a drug utilisation study using self-reported data from BELpREG, a prospective, web-based pregnancy registry established in November 2022. Pregnant individuals aged [≥]18 years receiving healthcare in Belgium can enrol voluntarily at any stage in pregnancy and complete online questionnaires at enrolment and every four weeks until delivery. All participants with follow-up beyond the first trimester were included, and trimester-specific cohorts were constructed based on completion of questionnaires after each trimester. Data were extracted in July 2025. ResultsThis study included 2,096 participants, of whom 1,767 were followed through trimester 2 and 1,136 through trimester 3. Median gestational age at enrolment was 16 weeks. Prevalence estimates of medication use were 80.2% in the six months before conception, 85.8% in trimester 1, 92.0% in trimester 2, and 94.9% in trimester 3. The most common classes were analgesics, vaccines, antihistamines, antianemic preparations, and drugs for acid-related disorders. Paracetamol was most frequently used (35.4% in trimester 1), typically short term (median 3 days), followed by doxylamine-pyridoxine (26.7% in trimester 1). Folic acid supplementation was nearly universal, though only 59.9% met national guideline-concordant criteria. Maternal vaccine uptake was substantial but incomplete, with 67.2% receiving pertussis, 41.5% influenza, and 21.5% COVID-19 vaccination. Exposure to potentially inappropriate or teratogenic medications was rare. ConclusionsMedication use during pregnancy in Belgium was nearly universal, with high use of paracetamol and doxylamine-pyridoxine. Folic acid and vaccine uptake were substantial, but often not guideline-concordant. Key PointsO_LIMedication use during pregnancy in Belgium was nearly universal, with over 85% of participants reporting use in the first trimester and 95% in the third. C_LIO_LIParacetamol (35% in the first trimester) and doxylamine-pyridoxine (27% in the first trimester) were the most frequently used medications. C_LIO_LIFolic acid use was widespread, yet only about 60% of participants followed national timing and duration recommendations. C_LIO_LIMaternal vaccine uptake was substantial, particularly for pertussis (67%), though not universal despite guideline recommendations C_LIO_LIBELpREGs self-reported data capture both prescription and over-the-counter medications, offering a complete picture of real-world use during pregnancy. C_LI Plain Language SummaryThis study looked at how often and when people in Belgium use medications, folic acid supplements, and vaccines during pregnancy. Using data from the BELpREG pregnancy registry, more than 2,000 pregnant participants completed online questionnaires about their health and medication use throughout pregnancy (every four weeks). Almost everyone reported taking at least one medication: 86% during the first trimester and 95% during the third. The most common medicines were paracetamol and doxylamine-pyridoxine. Nearly all participants used folic acid, but only about 60% followed national recommendations for starting timely before pregnancy and continuing through the first trimester. Many received recommended vaccines during pregnancy: about 67% for pertussis, 42% for influenza, and 22% for COVID-19; but uptake was still incomplete. Exposure to potentially inappropriate or teratogenic medications was rare. Because BELpREG collects self-reported data, including both prescribed and over-the-counter products, it provides a comprehensive picture of real-world medication use in pregnant people. Further, these findings help identify gaps between guideline recommendations and actual practice. Social Media QuoteMedication use in pregnancy is nearly universal in Belgium. Paracetamol and doxylamine-pyridoxine top the list. Folic acid and vaccine uptake are high but often not guideline-concordant. BELpREG data reveal unique self-reported real-world patterns. #BELpREG