diff --git a/nwbinspector/checks/nwbfile_metadata.py b/nwbinspector/checks/nwbfile_metadata.py
index 3137ed5e1..81e4ed903 100644
--- a/nwbinspector/checks/nwbfile_metadata.py
+++ b/nwbinspector/checks/nwbfile_metadata.py
@@ -161,6 +161,18 @@ def check_subject_proper_age_range(subject: Subject):
             )
 
 
+@register_check(importance=Importance.BEST_PRACTICE_SUGGESTION, neurodata_type=Subject)
+def check_subject_age_reference(subject: Subject):
+    """Check if the Subject age reference is one of supported options."""
+    valid_options = ["birth", "gestational", None]
+    if subject.age__reference not in valid_options:
+        return InspectorMessage(
+            message=(
+                f"Subject age reference, '{subject.age__reference}', is not one of the valid options ({valid_options})."
+            )
+        )
+
+
 @register_check(importance=Importance.BEST_PRACTICE_SUGGESTION, neurodata_type=Subject)
 def check_subject_id_exists(subject: Subject):
     """Check if subject_id is defined."""
diff --git a/nwbinspector/internal_configs/dandi.inspector_config.yaml b/nwbinspector/internal_configs/dandi.inspector_config.yaml
index 4463ea1b2..22df25e5e 100644
--- a/nwbinspector/internal_configs/dandi.inspector_config.yaml
+++ b/nwbinspector/internal_configs/dandi.inspector_config.yaml
@@ -5,5 +5,6 @@ CRITICAL:  # All the fields under CRITICAL will be required for dandi validate t
   - check_subject_species
   - check_subject_age
   - check_subject_proper_age_range
+  - check_subject_age_reference
 BEST_PRACTICE_VIOLATION:
   - check_data_orientation  # not 100% accurate, so need to deelevate from CRITICAL to skip it in dandi validate