It worked in the short term. "A" got him to live with her, she had to go out partying with him to keep him remotely interested but she didn't do drugs or drink she just got to watch him doing so while she got bigger and bigger throughout the pregnancy and desperately tried to stay attractive to him.
Then he walked out when the baby was 5 weeks old. She came to stay with me for a month at that point as she had become suicidal after he left. We (my first husband and I) were living abroad in a lovely beachy area so she stayed for a lovely holiday and went back calm and clear headed.
Unfortunately, once back in the country she continued to chase him, and this became and on and off thing for a couple of years.
She then moved to another country which had always been her dream, he happily signed off on her removing his son from the UK when the boy was about 2 years old. But then the prospect of a shag and a nice long holiday loomed large so followed her out there for a one month holiday and while there he proposed.
Then he went back home and dumped her again over the phone, upon which she chased him back to the UK, removing her son from his nursery, leaving her good job and the Australian weather and lifestyle and moving back in with her mum in a council flat.
It was absolutely horrific to be honest, the whole thing. Just heartbreaking and terrible. I found her on FB a few years ago (I am not on FB anymore), I didn't contact her but I saw she had a new second name, was married with more kids and seemed to be doing ok. I do hope she found happiness because what he put her through and what she put herself through by chasing after him was honestly soul destroying.
The other one, C, managed to pester him into marrying her. He loved to cheat and even came on to me on one occasion. I didn't tell her because at that point she had already told me about him repeatedly cheating and I figured she'd dump me and not him and be even more isolated. Then he hit her, at least once. She got divorced a couple of years later and seems to be ok on her own, though I haven't heard from her in a long time.
Based on these experiences, I would advise anyone who feels they need to trick a man into fatherhood to hang on to him to think again about the sort of man they are trying to entrap. Good men generally don't need to be caught, and good relationships are founded on shared goals and respect.