Should homeless women be "bribed" to have contraception implants?

In a programme on Radio 4 on Thursday  "Inside the Ethics Committee" a doctor had proposed that homeless women should be offered £20 to have an implant which would keep them from conceiving for three years.  This was considered very, very controversial, but what struck me about the discussion was the it concentrated on the rights or otherwise of the women and did not at all address the rights of the unborn child which would, almost by definition, be taken into care at birth.  Some of the women mentioned had had five or six children, all taken away from them.  Surely it isn't fair to let a child be born knowing that it will not have a family and a home.  I find it totally moral to offer this £20 and wonder if others feel the same.