Tabbylady thats exactly what happened with my friend. Police turned up at her home and escorted her and her dd to hospital. SS turned up. Police hung around, and it was made clear to friend she wouldn't be allowed to leave with her dd. DD was checked, no evidence of abuse found, but SS weren't happy and gave friend the ultimatum.
Friend was concerned that as her dd has SN, she would find it incredibly difficult to be in foster care, and she was worried they wouldn't know how to care for her properly. So friend voluntarily agreed to her sister taking her dd, with friend having supervised visits in a contact centre.
Friend was under the impression that it would only be for a couple of days, but SS went to court, and got some sort of order (I don't now what exactly), that meant that friend couldn't get her dd back without a court hearing.
The hearing kept getting delayed, as SS were preparing reports, didn't have the necessary evidence etc, during this time friend voluntarily attended several courses suggested by SS, as her solicitor said it would help her get her dd back.
It took 6 months to get a court date, at which point SW turned up in court and said there were no concerns about the mother, and they had no objection to the order being overturned and the dd being returned to her.