Upper house MPs will this week consider a raft of proposed amendments on the bill to decriminalise abortion, more than a month after it passed the lower house 59-31.

The draft legislation would allow terminations up to 22 weeks - and later, with the consent of two doctors.

Liberal and Labor MPs have been allowed a conscience vote on the private member's bill, with opponents raising concerns about late-term abortions, conscientious objection, gender-based terminations and the way in which the bill was introduced.

A cross-party group of MPs, which includes Shooters MP Robert Borsak, One Nation MP Mark Latham, Labor MP Courtney Houssos and Liberal MP Natasha Maclaren-Jones, is pushing a number of proposed amendments in the upper house.

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Under their amendments, medical practitioners wouldn't perform terminations believed to be for sex selection, and they would take all reasonable steps to ensure neonatal care for babies born alive from a termination.

Another change would require that terminations after 20 weeks are only done to save the life of a mother or another unborn child.

But the amendments have been criticised by the NSW Pro-Choice Alliance, which says they would "devastate" women's access to healthcare.

"The Reproductive Health Care Reform Bill as it stands is an appropriate and conservative approach to decriminalising abortion and regulating it as the health procedure it is," alliance chair Wendy McCarthy said.

Rallies both in favour and against the bill were held over the weekend, with a pro-choice event on Saturday and anti-abortion event on Sunday in Hyde Park.

Protesters supporting the bill urged politicians to forgo the proposed list of amendments, saying many could "make things worse for women than they currently are".

Those who demanded the withdrawal of the bill, such as ex-prime minister Tony Abbott, called the draft laws "infanticide on demand". Ex-Nationals leader Barnaby Joyce said abortion was "the slavery debate of our time".

NSW Premier Gladys Berejiklian - who voted in favour of the bill in the lower house - said she was confident amendments would be passed in the upper house.

"I can assume that there'll be amendments passed in the upper house - whether or not they satisfy every single person, I can't make that judgement," she told 2GB on Friday.

Australian Associated Press