diff --git a/paths/qoc_checkupList_{setKey}.yaml b/paths/qoc_checkupList_{setKey}.yaml
index eb32c23..c40a43b 100644
--- a/paths/qoc_checkupList_{setKey}.yaml
+++ b/paths/qoc_checkupList_{setKey}.yaml
@@ -19,6 +19,17 @@ get:
       required: false
       schema:
         $ref: ../schemas/date.yaml
+    - name: birthMonth
+      in: query
+      description: |-
+        Restricts the patient list to those born in the specified month and those with no birthdate (rare case). The list of gp's is limited to those who are responsible to the patients in the restricted list. The initial calculation of the call-up list is not affected by the parameter.
+
+        If the parameter is omitted or specified outside its boundaries, then all patients are returned.
+      required: false
+      schema:
+        type: integer
+        minimum: 1
+        maximum: 12
     - name: addr
       in: query
       required: false