Women’s groups in Brazil are set to challenge the abortion laws this summer in the hope of making a safe and legal termination possible for women at risk of delivering a baby born with defects after exposure to the Zika virus.

“Women should be able to decide and have the means to terminate pregnancies because they are facing serious risks of having babies with microcephaly and also suffering huge mental distress during their pregnancies. They should not be forced to carry on their pregnancies under the circumstances,” said Beatriz Galli, a lawyer on bioethics and human rights who works for Ipas, a group dedicated to ending unsafe abortion.

Lawyers for the organisations will present a legal challenge at the supreme court in the first week of August, when the court sits again after the winter break. They are co-ordinated by Anis Instituto de Bioética, which campaigns for women’s equality and reproductive rights.

The groups have obtained an opinion from lawyers at Yale University in the US, who argue that the Brazilian government’s policies on Zika and microcephaly have breached women’s human rights. The government “has failed to enact adequate measures to ensure that all women have access to comprehensive reproductive health information and options, as required by Brazil’s public health and human rights commitments”, says a review from the Global Health Justice Partnership, which is a joint initiative of the Yale Law School and the Yale School of Public Health.It is also critical of Brazil’s handling of the epidemic. Its “failure to ensure adequate infrastructure, public health resources and mosquito control programmes in certain areas has greatly exacerbated the Zika and Zika-related microcephaly epidemics, particularly among poor women of racial minorities”, the review says.

As of 7 July, there have been 1,638 cases of reported microcephaly – an abnormally small head – and other brain defects in Brazil, according to the World Health Organisation. Women who do not want to continue their pregnancy because they have been infected, even if they have had a scan confirming brain defects in the baby, are unable to choose a legal termination. There is evidence of a rise in early abortions using pills obtainable online and fears that unsafe, illegal abortions will be rising too.

Galli said there were already about 200,000 hospitalisations of women who have undergone a clandestine termination every year, and a suspected 1 million illegal abortions before the epidemic. “We know that there are clinics operating in the very low-income poor settings in Rio and women are paying a lot of money and are risking their lives,” she said.

Campaigners who want to change the law are encouraged by a ruling the supreme court handed down in the case of babies with anencephaly in 2012. This is a condition where the foetus develops without a brain, making it impossible for the baby to be born alive. The case took eight years, but eventually the court voted eight to two in favour of making abortion legal in those circumstances.

Before the ruling, there were two exceptions to the ban on termination in Brazil – when the pregnant woman’s life was at risk and when she had been raped. Anencephaly became the third, but campaigners acknowledge that it is not a simple precedent.

Debora Diniz, co-founder of Anis and professor of law at the University of Brasilia, said she was confident the court would understand that the situation is an emergency. They were not asking for the legalisation of abortion, she said, but “to have the right to abortion in the case of Zika infection during the epidemic”.

“It is not an abortion in the case of foetal malformation. It is the right to abortion in case of being infected by the Zika virus, suffering mental stress because you have this horrible situation and so few answers on how to plan and have a safe pregnancy,” she said.

Campaigners have five demands: good information for women in pregnancy, improvements in access to family planning, giving women mosquito repellents, better social policies to help children born with birth defects because of Zika and financial support for parents.

Diniz points out that the worst hit are the poor. “The feeling in my well-to-do neighbourhood [in Brasilia] is that everything is fine,” she said. People have never met a woman with Zika or seen a baby with neurological defects. But when she goes to clinics in hard-hit areas such as Campina Grande in the north-east, everything revolves around Zika.

“We have two countries in one country,” she said. “This is an emergency of unknown women. The trouble is they were unknown before the epidemic. I’m not being an opportunist. We have an epidemic and the epidemic shows the face of Brazilian inequality.”