If the father has the right to determine the primary residence of the child, then he can designate where the child lives-- even if it's with a girlfriend.  Whenever it is a parent's time for possession of the child, he or she can also designate who they want to care for the child during their periods of possession.  So, yes, the father can leave the child to stay with his girlfriend for nine months -- as long as he is not denying you the court ordered periods of your visitation.  The exception to this rule would be the court order itself-- if the order prohibited him from leaving the child with this particular girlfriend or the girlfriend was not an otherwise appropriate caregiver-- then he could not leave the child with her.Even though what he is doing is permissible under the law and the court order, you can petition the court to modify the custody orders to grant you more access to the child while he is away.  You would have a strong policy argument in that it makes more sense to have a child raised by her biological parent than a stranger.  If the girlfriend tried to intervene, your rights would prevail over her's because she's a nonparent.