The Federal Government has no plans to phase in the increased baby bonus, despite academics' fears it will cause some women to delay birth to get the extra money.
Health Minister Nicola Roxon has also rejected as unfair criticisms that she and other female Cabinet ministers have abandoned women by referring the issue of paid maternity leave to the Productivity Commission.
Ms Roxon said yesterday that the "dates are fixed" for the July 1 change to the baby bonus, which will increase to $5000 from $4187.
Research by Australian National University economist Andrew Leigh and Melbourne University's Professor Joshua Gans suggests about 1000 babies that would have been born in June 2004 had their arrival delayed until July when the bonus was introduced mainly by postponing caesarean sections and inductions. This caused a bout of unhealthily heavy babies, they said.
Ms Roxon said the issue was a " bit overstated".
"I would be absolutely confident that doctors will be giving their patients the best clinical advice," she said on Meet the Press.
"It's obviously not sensible for people to make decisions based on financial arrangements rather than what's in the best interests of the child.
"But I really think that this is around the margins, probably a matter of a day or two, rather than there being some serious issues of doctors advising women to wait an extra month.
"Nature doesn't allow it, and it would of course be a risky thing to do."
Ms Roxon and other female federal cabinet ministers were also criticised yesterday by former sex discrimination commissioner and now NSW state Liberal MP Pru Goward over their handing of paid maternity leave.
She said Labor had effectively dropped the issue after gaining government. "To refer it to the Productivity Commission, which is not designed to look at anything other than business-related and microeconomic measures, for a year, is a sign a: that they're not sincere and b: that when they do it, they will probably impose it as a cost upon business," she said on ABC.
Ms Roxon said the criticism was unfair and the Productivity Commission would work out how to pay maternity leave in a way that would "work best both for mothers and their families, but also for the economy and for business".
ACT Health Minister Katy Gallagher said it was appropriate for a new government to get advice on a proposed model and the costs involved. However, there were "lots of women around the country who would like to see one in place sooner rather than later".
"I think it is progress forward, but it is slow," she said. "I think a fully funded paid maternity leave scheme in Australia is inevitable and it should be managed by the Federal Government, but again it is going to be a matter of time and cost."
Democrats Senator Natasha Stott Despoja welcomed Ms Roxon's commitment to introduce a paid maternity leave system. "The Australian Democrats have been calling for the Government to commit to introducing paid maternity leave after the Productivity Commission inquiry reports, but until now they have refused to make this commitment," her spokeswoman said.
However, the spokeswoman said the Democrats were concerned the Productivity Commission would further delay action on the issues, following examinations by both the Human Rights and Equal Opportunity Commission and a Senate inquiry.