I was watching a Customs enforcement show from the US and they rejected entry of a Nigerian woman because she was very pregnant. They assessed she and her husband were only coming there to gain citizenship for the child and basically a free birth. She put on a plane and sent back home and he was allowed in. If they intend to have the child here whether they can pay or not their entry should be rejected.
I was actually quite surprise of the outcome and would guess it would be different without the cameras.