Kerry Robertson, 17, who has mild learning difficulties, has been told that she will not be allowed to bring up her own child, who she has already named Ben.
Last month Miss Robertson was prevented from marrying her fiancé Mark McDougall, 25, after council officials claimed that she “did not understand the implications of getting married”.
She has now been warned that she will only be allowed a few hours with her baby, which is due in January, before it is taken into foster care.
After hearing the news, Miss Robertson, of Dunfermline, Fife, who is 26 weeks pregnant, said: “I couldn't believe it. I am so upset – I can't stop crying.”
Mr McDougall, an artist, said he wants to take on full responsibility for his son but claims that he is powerless because he is not married to Miss Robertson.
He added: “Social Services are ruining our lives. As we are not married – because social workers would not let us marry – it seems I have no rights as a dad at all.
“Kerry's gran is trying to apply for custody of Ben but social services have already told us it is unlikely she will be successful. We feel helpless.”
The extraordinary case first came to light last month when the couple’s wedding was halted 48 hours before Miss Robertson was due to walk up the aisle.
Under Scottish law, a registrar may refuse to marry a couple if they believe one or both the parties lack the mental capacity to understand what the institution of marriage is about.
In a highly unusual step, Dunfermline Register Office refused to sanction the marriage after Fife council wrote a letter of objection.
Miss Robertson was brought up by her grandmother from the age of nine months because her parents were unable to look after her and her welfare has since been overseen by the council’s social workers.
She met Mr McDougall, from Arbroath, in January and the couple planned to get married after Miss Robertson became pregnant.
Two days before the ceremony, two social workers visited their flat and told them that the marriage was illegal because of Miss Robertson’s learning difficulties.
The service and reception for 20 guests had to be called off despite the couple having already bought rings and a wedding dress.
At the time, Miss Robertson said: “I know what marriage is. It is when two folks want to spend the rest of their lives together. I love Mark and I want to get married to him.”
Mr McDougall added: “Despite arguing that we loved one another and didn't want our baby to be born to unwed parents, they would not budge. It's a nightmare.”
He claims that social services have exaggerated the extent of Miss Robertson’s learning difficulties and that she is hoping to go back to college to catch up academically.
The council said it does not comment on individual cases. But Stephen Moore, the council's executive director of social services, said: “Much of the work we do is governed by legislation. Complex decisions are made that balance risk and welfare while supporting people at times of personal or family need.
"We will always work with people for the best outcome for all involved.”
In May it was disclosed that Rachel Pullen, 24, had her three-year-old daughter taken away from her by social services when she was six months old after Nottingham City Council officials deemed her too stupid to look after the child.
