diff --git a/StandardizedClinicalDataTables/OBSERVATION_PERIOD.md b/StandardizedClinicalDataTables/OBSERVATION_PERIOD.md
index d88ec4a..e83bf65 100644
--- a/StandardizedClinicalDataTables/OBSERVATION_PERIOD.md
+++ b/StandardizedClinicalDataTables/OBSERVATION_PERIOD.md
@@ -1,7 +1,7 @@
 The OBSERVATION_PERIOD table contains records which uniquely define the spans of time for which a Person is at-risk to have clinical events recorded within the source systems, even if no events in fact are recorded (healthy patient with no healthcare interactions).
 
 Field|Required|Type|Description
-:----|:----|:-----|:-----
+:------------------------------|:--------|:-----|:----------------------------------------------
 |observation_period_id|Yes|integer|A unique identifier for each observation period.|
 |person_id|Yes|integer|A foreign key identifier to the person for whom the observation period is defined. The demographic details of that person are stored in the person table.|
 |observation_period_start_date|Yes|date|The start date of the observation period for which data are available from the data source.|