(315) The BELpREG Registry on Perinatal Medication Exposure and Mother-Infant Outcomes: Preliminary Insights into this unique Pregnancy Cohort in Belgium

Background: BELpREG is the Belgian pregnancy registry collecting real-world data on perinatal medication exposure and mother-infant outcomes via online self-reported questionnaires. Upon enrollment, women complete a first questionnaire, after which they receive follow-up questionnaires each four weeks until eight weeks postpartum. Additionally, mothers receive questionnaires on child development at 6 and 12 months after birth.

Objectives: To determine the characteristics of the cohort included in the first year of the BELpREG registry, including prevalence estimates and type of medication used as well as longitudinal follow-up rates.

Methods: Data collection started in November 2022. All pregnant women, ≥18 years, and followed up by any Belgian healthcare service can enroll. On December 7th, 2023, data were extracted for this cross-sectional, descriptive analysis. Characteristics of participants were compared with Belgian population statistics.

Results: In total, 656 women consented for participation, with overall 549 having fully completed the enrolment questionnaire (83.7%). Most participants were between 25-34 years (84.8%) and were recruited via social media (53.8%) or healthcare professionals (22.9%). Median gestational age at enrolment was 18 weeks. Completion rates for the 1st, 2nd and 3rd follow-up during pregnancy and the two postpartum questionnaires were 81.1%, 74.4%, 73.1%, 88.1% and 81.0%, respectively. Compared to the non-pregnant population, more participants had a high educational level (85.2% vs. 52.0%) and more women were employed (97.0% vs. 82.2%). More pregnancies following a fertility treatment were included (18.6% vs. 8.2%). A chronic condition before the start of the pregnancy was reported by 36.4% of women, mainly allergic conditions (9.9%), asthma (4.3%), and migraine (4.2%). In the first questionnaire, 87.1% indicated having used a medication since the start of the pregnancy. Analgesics (45.0%), systemic antihistamines (37.5%), vaccines (18.9%), drugs for acid-related disorders (15.2%) and antianemic preparations (13.4%) were the most frequently reported categories, with paracetamol (43.1%) and doxylamine/pyridoxine (26.1%) as the most often reported active compounds. BELpREG also contains cases with less studied medicines in pregnancy (e.g., lacosamide and tacrolimus), and inappropriate medicines in pregnancy (e.g., oral ibuprofen and pseudo-ephedrine).

Conclusions: Perinatal medication exposure and outcome data are being collected in the BELpREG registry. The registry's capacity to collect data on less studied medications, along with the growing engagement of participants in recent months, underscore its potential as a promising research tool.