A young woman with learning difficulties who faced the prospect of a court deciding if her pregnancy should be terminated has the capacity to decide herself, the high court has ruled.

The woman, who cannot be named for legal reasons, has sickle cell disease which has already caused her to have a series of strokes, and is 18 weeks' pregnant.

The declaration that she has the capacity to decide whether to continue or terminate the pregnancy came after concerns were raised that it might be appropriate for the court of protection to intervene and decide what was in her best interests.

Mr Justice Hedley, sitting in the court of protection, said the woman, who is from the south of England, "manifestly lacked capacity" to participate in legal proceedings at the present time and required the assistance of the Official Solicitor to act as her "litigation friend".

But an independent expert in psychiatry, Dr Stephen Tyrer, said she did have capacity "to decide whether or not to continue with, or terminate, pregnancy".

The judge said it was now also the position of all parties and all witnesses that she had capacity, and, "that being so, the court of protection has no jurisdiction to engage in an assessment of her best interests".

"It is right to observe that both expert and professional and family evidence in the case is it would be in her best interests to continue with the pregnancy, but that is outwith the jurisdiction of this court."

He said it was important to bear in mind that people with severe learning difficulties, who might not be able to function independently in the community in many other aspects of their lives, "may very well retain the capacity to make deeply personal decisions about how they conduct their lives". This could include decisions about choice of partners, the extent of sexual activity, making permanent relationships, "and decisions about their own medical care including, as in this case, the continuation or termination of pregnancy".

The woman was born with sickle cell disease, a lifelong genetic medical condition which resulted in her requiring medical treatment and made her prone to strokes. A number of strokes had left her with learning difficulties and placed her in the bottom 1% of the population in terms of intellectual functioning.

She had sued over her treatment and received a substantial award in settlement of a claim.

Her disadvantages meant she required deputies to act as administrators on her behalf – one being her mother, the other a firm of solicitors. She lives with her mother, sister and other members of her family.

Towards the end of last year she discovered she was pregnant and the matter was brought to the attention of the court. There was a belief that the father was known, but it would not be right for the court to make any observation about that, the judge said.

"However, entirely respectable anxiety was raised about her capacity to deal with these matters, in particular her capacity to decide whether or not she wished to continue with the pregnancy".