iOS Core Data - Deletes not reflected until App Restart

I am successfully adding and updating records in my core data on a second thread without issue.

However, deletes don't seem to take effect until I stop and restart the App. So the delete is obviously working to a extent. I read the data before loading the tableview and don't do anything different for when there has been a deletion.

The code I'm using is

....fetch records....
BOOL deleteGem = FALSE;
if ([[attributeDict objectForKey:@"headline"] hasPrefix:@"VOID"])
    deleteGem = TRUE;

    if ([mutableFetchResults c开发者_开发问答ount] == 0) {
    // not there so create a new one    
        if (!deleteGem) {
            // so create a new one unless it needs deleting
            gem = (Gem *)[NSEntityDescription insertNewObjectForEntityForName:@"Gem" inManagedObjectContext:managedObjectContext];
            [gem setID:[attributeDict objectForKey:@"ID"]];
        }
    } else {

        // already exists so either get it and then update or delete it
        gem = [mutableFetchResults objectAtIndex:0];

        if (deleteGem) {
            // delete it if required
            [managedObjectContext deleteObject:gem];
            gemDeletes ++;
        }
    }
    .....

Later on I have a method to save any updates including:

    NSError *error;
    if (![self.managedObjectContext save:&error]) { 
    ....

Any ideas warmly welcomed...

Edit - with full answer based on @TechZen's answer..

Register for notifications of updates on the 2nd thread in viewDidLoad

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleSaveNotification:) name:NSManagedObjectContextDidSaveNotification object:nil];

Unregister for notifications in viewDidUnload

[[NSNotificationCenter defaultCenter] removeObserver:self name:NSManagedObjectContextDidSaveNotification object:nil];

Handle the update in the main thread (a new method in the view controller)

-(void)handleSaveNotification:(NSNotification *)aNotification {
    [managedObjectContext mergeChangesFromContextDidSaveNotification:aNotification];
}

You have to merge the background context with the foreground context if you want the changes made in the background context to show up in the foreground context.