If you will give copper mid-pregnancy, as you may need to do depending on your sheep breed(s) and local deficiencies, then you may need to be cautious about giving chelated or otherwise longlasting copper now
If you are using a chelated - ie top quality - drench mid-pregnancy then you can probably use a cheaper one now.
Which one depends on your local conditions and the breed and condition of your sheep... Up here we would mostly give a short-term copper-cobalt-selenium drench now, or without copper for Texel sheep, with the full-blown chelated drench mid-pregnancy.