Northern Ireland's strict abortion law breaches the UK's human rights commitments, the High Court in Belfast has ruled.
Sarah Ewart, 29, hailed a "massive victory" following a six-year legal battle since she was refused a termination in 2013.
She travelled to a London clinic to end her pregnancy after doctors said her unborn child would die in the womb or shortly after birth.
Following Thursday's judgment she said: "Today's ruling is a turning point for women in their campaign against the outdated laws prohibiting abortion in Northern Ireland.
"It should never have come to this.
She said the case had been "a massive stress emotionally on all the family".
Mrs Justice Siobhan Keegan said her testimony had been compelling.
She decided it was not right that another young woman would be required to pursue litigation and face the same "trauma and pain" in the future.
She said: "I cannot see that this would serve any benefit or it would be right to ask another woman to re-live the trauma.
"In my view her personal testimony is compelling."
The judge said a formal declaration of incompatibility would not be made at this stage.
Abortion is likely to be legalised in Northern Ireland next year unless Stormont's Assembly is restored within weeks.
MPs at Westminster voted for the measure earlier this year.
The devolved institutions at Stormont have been suspended for two-and-a-half years and that has contributed to inaction over the matter.
Ms Ewart's child was diagnosed with a fatal fetal abnormality; her brain was not properly developed and she would have died during pregnancy or soon after birth.
The young mother was told she could not have a termination in Northern Ireland and was given no advice about where to find one.
The judge said: "She has had to modify her behaviour in that she could not have medical treatment in Northern Ireland due to the risk of criminal prosecution."
She has since had two children but wants to have more and fears a similar situation could happen again, the judge said.
Abortion is only permitted in Northern Ireland if a woman's life is at risk or if there is a risk of permanent and serious damage to her mental or physical health.
Rape, incest or diagnoses of fatal fetal abnormality are not grounds for a legal abortion.
Northern Ireland's chief medical officer has criticised the law surrounding cases similar to Ms Ewart's.
The case was taken in Belfast after an earlier abortion challenge in the Supreme Court was dismissed on the technicality that the Northern Ireland Human Rights Commission did not have legal standing to bring the judicial review.
In response Ms Ewart launched proceedings in Belfast.
She said: "It is a massive emotional relief.
"This has not been an easy journey."