diff --git a/R/Export.R b/R/Export.R
index 97ae2ad..5c542be 100644
--- a/R/Export.R
+++ b/R/Export.R
@@ -256,6 +256,7 @@ exportExposuresOutcomes <- function(outputFolder, exportFolder) {
 
     exposuresOutcomeSet <- tibble(
       exposuresOutcomeSetId = i,
+      nestingCohortId = eso$nestingCohortId,
       outcomeId = eso$outcomeId
     )
     sccsExposuresOutcomeSet[[length(sccsExposuresOutcomeSet) + 1]] <- exposuresOutcomeSet
diff --git a/inst/csv/resultsDataModelSpecification.csv b/inst/csv/resultsDataModelSpecification.csv
index 2b80332..146e9cc 100644
--- a/inst/csv/resultsDataModelSpecification.csv
+++ b/inst/csv/resultsDataModelSpecification.csv
@@ -21,6 +21,7 @@ sccs_era,era_name,varchar,No,No,No,A name for the era. Is NULL for eras derived
 sccs_era,database_id,varchar,Yes,Yes,No,Foreign key referencing the database.
 sccs_exposures_outcome_set,exposures_outcome_set_id,int,Yes,Yes,No,A unique identifier for a set of exposures and an outcome.
 sccs_exposures_outcome_set,outcome_id,int,Yes,No,No,A cohort ID.
+sccs_exposures_outcome_set,nesting_cohort_id,int,No,No,No,A cohort ID.
 sccs_exposure,exposures_outcome_set_id,int,Yes,Yes,No,A foreign key referencing the sccs_exposures_outcome_set table.
 sccs_exposure,era_id,int,Yes,Yes,No,A foreign key referencing the sccs_era table.
 sccs_exposure,true_effect_size,float,No,No,No,"If known, the true effect size. For negatitive controls this equals 1."
diff --git a/inst/sql/sql_server/migrations/Migration_2-v5_1_0.sql b/inst/sql/sql_server/migrations/Migration_2-v5_1_0.sql
new file mode 100644
index 0000000..f9cfe06
--- /dev/null
+++ b/inst/sql/sql_server/migrations/Migration_2-v5_1_0.sql
@@ -0,0 +1,5 @@
+-- Database migrations for version 5.1.0
+-- This migration updates the schema:
+ -- 1. Adds the nesting_cohort_id to the sccs_exposures_outcome_set table
+
+ALTER TABLE @database_schema.@table_prefixsccs_exposures_outcome_set ADD nesting_cohort_id FLOAT