MPs will have to contend with dozens of amendments to the abortion decriminalisation bill on Thursday, as supporters and opponents were on Wednesday night frantically drafting changes.

It is expected one of the co-sponsors of the bill, Nationals MP Leslie Williams, will move amendments in a bid to allay concerns over late-term abortions.

Gladys Berejiklian is not expected to speak during the debate on decriminialising abortion. AAP

It is understood Premier Gladys Berejiklian, who has previously said she would support the bill, has concerns around late-term abortions.

Other amendments are also likely to come from Labor and Liberal backbenchers, as well as independent MP Joe McGirr, who is a medical doctor.

One senior government source said: "There will be a whole bunch of well intentioned amendments that contradict each other and you could well end up with something that is unreadable that becomes law."

Ms Berejiklian is unlikely to speak on the bill to decriminalise abortions, but is expected to support some amendments amid an intensifying debate over the regulation of late-term abortions.

It comes as the NSW Australian Medical Association (AMA) warned the bill risked being "derailed by unfounded fearmongering on abortion", and slammed a raft of amendments proposed by NSW Attorney General Mark Speakman and Planning Minister Rob Stokes.

The AMA said the amendments, which impose additional requirements around abortions performed after 22 weeks, "go against the spirit in which the bill was introduced – in fact, they are a perversion of it."

"[I]f voted into law, they would mean access to abortion in NSW would become very restrictive by Australian standards," the AMA said in a statement.

The "most concerning" amendment, the AMA said, was the move to require "a hospital advisory committee" comprising a four-person panel approve all terminations after 22 weeks.

"This would place women at significant risk of unnecessary delay and only add to their suffering, particularly women in regional and rural areas."

The Royal Australian and New Zealand College of Obstetricians and Gynaecologists also criticised the amendments, saying they "call into question the standards and ethics of the medical profession."

Anti-abortion campaigners protesting outside NSW Parliament on Tuesday. Louise Kennerley

Liberal MP Kevin Conolly has also proposed a package of amendments, which include lowering the threshold to 20 weeks, and a requirement that women be offered counselling.

Deputy Premier John Barilaro will also not speak, but has said he will "support the bill in full."

Labor leader Jodi McKay will support it. Ms McKay said a woman's decision to have an abortion "is a deeply personal one between her and her doctor.

"How she justifies that decision and the path that leads her to it is a matter for her and her alone."

MPs from across the political divide have indicated they will support amendments, as many put on the record their concerns with the bill's regulation of abortions after 22 weeks.

These include Treasurer Dominic Perrottet, Customer Service Minister Victor Dominello, Labor's TAFE spokesman Jihad Dib, and Shooters, Fishers and Farmers MPs Roy Butler and Philip Donato.

Mr Donato and Agricultural Minister Adam Marshall were among those who said they supported decriminalisation, but were still likely to support some amendments.

Mr Stokes, on Tuesday night, said the amendments would "ensure that late-term abortions are only conducted by highly qualified specialists with appropriate peer review."

The amendments will also require termination after 22 weeks to be performed by a "specialist medical practitioner" in a public hospital, or in a private hospital approved by the Health Minister.

They will also include a legislative requirement for women to give "informed consent", something the AMA said was "unnecessary and insulting" as doctors were required to obtain consent.

Local Government Minister Shelley Hancock, who is supporting the bill, hit out at her Liberal colleagues for attempting to change the bill.

"I implore many of the men in this chamber who have moved amendments to stop dabbling in the lives of women. Stay out of the lives of women," Ms Hancock said.

"There are no complications in this bill. None."

She added she would consider "sensible amendments" but not those "designed to defeat and defer this bill".

The decriminalisation bill, introduced by independent MP Alex Greenwich, allows abortion on request for women up to 22 weeks' gestation performed by a registered doctor.

Women beyond 22 weeks would need the consent of two doctors.

Mr Greenwich said he was "concerned" about how the amendments would impact "women's access to safe and legal abortion" and was working with the proponents, alongside medical and legal experts, to "address and resolve these concerns".