lifting guidelines

Recently an employer asked for manual lifting guidelines for pregnant workers.  The reason for their question was because a female employee who was in her first trimester of what appeared to be a healthy, normal pregnancy came to them with a note from her physician stating she should not exceed lifting 20 lbs for the remainder of her pregnancy.  They’ve had several pregnant workers in the past who never brought such a note to them so they wondered if there were new weight limit guidelines or if was a physician that was being very cautious.  Since this company had a number of positions that