Poland's constitutional court has ruled that abortions due to birth defects, which make up a majority of all legal terminations in Poland, are unconstitutional.
The country's laws on abortion were already some of the strictest in Europe.
Abortion will still be allowed if the mother's life or health are at risk and if the pregnancy is a result of a prohibited act, like rape.
The decision means abortion is unconstitutional in cases where the mother risks giving birth to a seriously ill child or one with no chance of survival.
Hours later after the ruling, hundreds of mostly young protesters defied a pandemic-related ban on gatherings and staged a protest before the court with signs saying "You have blood on your gowns" and "Shame".
The demonstrators then walked to the offices of the main ruling conservative Law and Justice (PiS) party, and to the house of party leader and deputy prime minister, Jaroslaw Kaczynski, who is the driving force behind the government's policies. Police cordoned the house off from protesters who were calling for the government to step down.
Officers briefly tussled with some people, took their banners and sprayed pepper gas to disperse the crowd.
PiS MPs issued the legal challenge last year against a 1993 law permitting abortion in cases of severe foetal disabilities. A majority of judges in court for Thursday's ruling were nominated by the ruling party.
A citizen's bill, backed by many in PiS, which moved to tighten abortion legislation in the Catholic country in 2016, was scrapped after when large protests broke out.
The Council of Europe's Commissioner for Human Rights Dunja Mijatovic called it "a sad day" for women's rights.
"Throwing in the topic of abortion and holding a pseudo-tribunal on it in the middle of a raging pandemic is more than cynicism. This is political villainy," said former Polish PM and President of the European Parliament Donald Tusk.
Human rights groups have also hit out against the ruling.
"The result will be agonising for women and their families, forcing some to continue through pregnancies against their will, including in cases of fatal or severe foetal impairment, while others will have no choice but to travel abroad to seek care if they have the financial means to do so, or to seek underground abortions," Irene Donadio from NGO International Planned Parenthood Federation told Euronews in a statement.
NGOs Amnesty International, the Center for Reproductive Rights and Human Rights Watch had said they would send independent monitors to the hearing.
They said in a joint statement: "Given our longstanding and publicly expressed concerns about the human rights of women and girls that are at stake, we view it as essential to observe the proceedings in this important case.
"The constitutional tribunal’s upcoming proceedings take place in the context of repeated government attacks on women’s rights and efforts to roll back reproductive rights, as well as legal and policy changes that have undermined the independence of the judiciary and rule of law in Poland."
The European Commission has expressed serious concerns regarding breaches of the rule of law in Poland and has proposed linking funding for member states to respect for this value.