Health authority and social services bosses had asked Mr Justice Cobb to authorise forced entry into the woman's home, the use of ''necessary restraint'' and sterilisation, at a hearing in the Court of Protection - where issues relating to sick and vulnerable people are examined - in London.
They argued such moves were in the best interests of the woman, who is 36.
Specialists said the woman had physical health problems which could put her life in danger if she became pregnant again.
Officials acknowledged that the rulings they wanted were ''extraordinary'' but said the woman's health - and life - could be at ''grave'' risk if action was not taken.
Mr Justice Cobb today granted their applications.
The judge described the case as "exceptional" and said the circumstances were "extreme".
He said the case was not about eugenics and that a further pregnancy could threaten the woman's life.
Mr Justice Cobb did not identify anyone involved.
"The ethical, legal and medical issues arising here are self-evidently of the utmost gravity, engaging, and profoundly impacting upon (the woman's) personal autonomy, privacy, bodily integrity, and reproductive rights," Mr Justice Cobb explained in his written ruling.
"This is, in my judgment, an exceptional case on its facts; the applicants seek a range of relief which is likely to arise only in the most extreme circumstances."
The judge said the woman had a history of concealing or attempting to conceal pregnancies from health professionals.
And he added: "This case is not about eugenics.
"This outcome has been driven by the bleak yet undisputed evidence that a further pregnancy would be a significantly life-threatening event for (the woman).
"The applicants' obstetric, gynaecological and contraceptive experts strongly recommend this treatment for (the woman), jointly expressing themselves in these stark terms: 'The risk to (the woman) of a future pregnancy, especially if concealed, is highly likely to lead to her death'."
Mr Justice Cobb declared that the woman lacked the mental capacity to litigate and make decisions regarding contraception.
The judge concluded that "therapeutic sterilisation" would be lawful and in the woman's best interests.
He authorised medics and social services staff to: "Remove (the woman) from her home and take steps to convey her to hospital for the purposes of the sterilisation procedure."
And he said "necessary and proportionate steps" could include "forced entry and necessary restraint".
The New Oxford Dictionary of English defines "eugenics" as:
The science of improving a population by controlled breeding to increase the occurrence of desirable heritable characteristics. Developed largely by Francis Galton as a method of improving the human race, it fell into disfavour only after the perversion of its doctrines by the Nazis.