Legislation to pardon women who have been convicted of illegal abortions has passed its final parliamentary hurdle, paving the way for a landmark change in the law in England and Wales.

The amendment to the crime and policing bill, which will also expunge the police records of those arrested and investigated over illegal abortions, was considered in the House of Lords during a phase of parliamentary ping-pong, where a bill passes back and forth between the Lords and Commons.

The bill is expected to receive royal assent – meaning it will become law – in the coming weeks. The same legislation will also put an end to prosecutions of women who terminate their own pregnancies, with a clause in the bill introduced in the Commons last year by the Labour backbencher Tonia Antoniazzi.

“I’m very pleased that parliament has approved a protection for women already harmed by outdated criminal law related to abortion. This will mean a great deal to these women who have been through an awful ordeal,” Antoniazzi said.

“Automatic pardons for convictions or cautions, and expunging the records of arrests and investigations, will enable these women to participate fully in society again, seeking the jobs and careers they’ve always wanted without having to repeatedly disclose and rehash their ordeal, travelling to places they wish to,” she added. “They can move through life without this hanging over them in the form of a record.”

Julia Porter Burke, a doctoral candidate at Columbia University writing a dissertation on the crime of abortion in England and Wales in the 19th century, found that “over a century, in all English and Welsh assize courts with extant records, only 20 women were charged with procuring their own abortions.”

While data on more recent abortion cases is patchy, figures suggest that as many women have been charged over the past 20 years as were in the entire 19th century.

Among the women who stand to be pardoned, as uncovered in Burke’s doctoral research, is Fanny Warboys, who in 1862 was the first woman criminalised under the 1861 Offences Against the Person Act.

Warboys was a widow who had a backstreet abortion and ended up grievously injured. After being told that she was likely to die, she told her doctor, and then the police, about the backstreet provider who had harmed her.

However, she survived – and was promptly put on trial and found guilty by a jury. “The prisoner, on hearing [the maximum sentence was penal servitude for life], here sank into the arms of the gaoler in a state of insensibility. On her recovery, the learned Judge sentenced her to three months’ imprisonment.”

Mary Jane Baynon, 32, was jailed for three months in 1891. A widow with children, she had travelled 500 miles, from her home in Sligo in western Ireland to London, to find a surgeon to provide an abortion.

While she sat waiting for her appointment, the man telephoned the police. It later transpired that he wasn’t a surgeon, but instead had been jailed for perjury and fined for falsely representing himself as a doctor.

As she was led away, Baynon addressed him in court, saying: “You might have let me go, if you didn’t intend to do it.”

There was also evidence in the court records of 19th-century judges showing compassion for women who found themselves before the courts.

In 1881, Emma Sarah Rice, 25, was found guilty of an illegal abortion, but she was still pregnant and in ill health, and was sentenced to just one day without hard labour. “His Lordship said he thought the woman was more to be pitied than condemned, and as far as punishment, it appeared to him that had been more than adequate already,” it was reported at the time.

However, while women will no longer be prosecuted, and those already convicted will be pardoned, there are concerns that women who are currently under investigation may still face criminalisation – even though their cases may not come to court until after the law has changed.

“Parliament has been clear that no woman should be criminalised for abortion and this is now set to become law,” Antoniazzi said.

“The police and CPS [Crown Prosecution Service] must hear that and stop current investigations – wasting public money investigating and prosecuting women for a crime which will no longer be a crime and for which they will then be automatically pardoned is, frankly, ludicrous.”

The CPS and the National Police Chiefs’ Council were approached for comment.