# Adapting the European Concerted Action on Congenital Anomalies and Twins (EUROCAT) Guide 1.5 for Use in Post‐Authorisation Safety Studies Using US Data

## TL;DR

This paper adapts a European guide for identifying birth defects into a US-friendly format using ICD-10-CM codes for safety studies.

## Contribution

The novel contribution is adapting the EUROCAT guide into a US-specific ICD-10-CM code list for congenital malformation classification.

## Key findings

- A final code list with 916 ICD-10-CM codes was created for 744 major and 172 minor malformations.
- The code list includes classifications and disease categories based on EUROCAT guidelines.
- The adapted list is ready for use in US post-authorization safety studies involving pregnancy.

## Abstract

Many post‐authorization safety studies focus on congenital malformations and rely on diagnosis codes found in US data sources. However, no authoritative standards exist for identifying and classifying malformations in these data. To address this, we translated an existing public health surveillance guide, the European Concerted Action on Congenital Anomalies and Twins (EUROCAT), into an ICD‐10‐CM code list for use in studies using US administrative healthcare data. The EUROCAT guide was selected for its decisive major or minor classification of each code. However, translation was required for use in US data sources since EUROCAT utilizes ICD‐10‐BPA which differs from ICD‐10‐CM (the coding system commonly encountered in US data sources).

We mapped EUROCAT to ICD‐10‐CM. For each code, manual review was conducted by two or more researchers, and major/minor classification was based on code descriptions since some codes differed between coding systems.

A final code list was created, containing 916 ICD‐10‐CM codes for 744 major and 172 minor malformations. The code list contains ICD‐10‐CM codes, their corresponding descriptions, their major or minor classification and disease category according to EUROCAT, and variables indicating anomalies caused by genetic or infectious diseases unlikely attributable to a medication.

We adapted the EUROCAT Guide 1.5 into an ICD‐10‐CM code list for use in pregnancy studies using US data sources. This list includes new ICD‐10‐CM codes available in 2024. As new ICD‐10‐CM codes become available, or as the EUROCAT Guide is updated, further updates to this list will be needed.