It's a joke on pro-abortion movements in the left wing political spectrum.
The joke plays on the exaggerated view that modern left wing or "liberal" women don't want kids and will therefore try to abort every pregnancy they have in favour of being independent and adopting (more) cats. Following that logic, it becomes a "minimum requirement" for babies of modern left wing women to be able to fence off the abortion equipment (here: coathanger hook) in the womb to have a chance of being carried to term and be born.
bye