An algorithm to identify pregnancies in BIFAP Primary Care database in Spain: Results from a cohort of 155 419 pregnancies.

Purpose: There has been a notable progress on the development of methods for identification of pregnancies using primary care databases. We aimed to evaluate the prescription of medications during pregnancy applying a novel algorithm.

Methods: We identified pregnancies in women aged 15 to 49 years registered in the Database for Pharmacoepidemiological Research in Primary Care (BIFAP) between 2002 and 2015. The algorithm applied sequential cycles that searched in hierarchical order for indicators of conception, delivery or pregnancy loss, and other codes suggestive of pregnancy. Length of pregnancy was assessed by searching for last menstrual period (LMP) date, gestational age, and outcomes of pregnancy. Prescription of specific drugs during the pre-pregnancy period and first trimester and time trends during pregnancy were evaluated.

Results: We identified a total of 155 419 pregnancies during the study period (77.5% completed pregnancies, 21.5% pregnancies losses, 0.8% ectopic pregnancies, and 0.2% stillbirths). Excluding vitamins and supplements, 43.8% of women received at least one prescription during the pre-pregnancy period and 68.4% during the first trimester. During the first trimester, the most commonly drugs prescribed were analgesics (16.3%) followed by antibiotics (11.8%). From 2002/2003 to 2014/2015, there was an increase of prescriptions for thyroid hormones (1.0% vs 4.7%), H2 blockers (1.0% vs 2.2%), and PPIs (1.4% vs 2.2%). While antidepressants (2.0% vs 1.5%) and benzodiazepines (3.1% vs 2.4%) decreased in the last period.

Conclusion: Having in mind the challenges of identifying pregnancies in health care databases, this study demonstrates the usefulness of BIFAP database for studies on drug utilization during pregnancy.