HARRISBURG - The battle over proposals to impose tougher standards at Pennsylvania's 20 abortion clinics took a new turn Monday as state senators voted to study what those standards would cost the clinics.

After an hour of heated debate, the Senate approved an amendment that would require the independent Legislative Budget and Finance Committee to conduct a study within 90 days of the bill's becoming law detailing additional costs that would be incurred by abortion clinics.

The amendment would not delay implementing the law, but it would address concerns that abortion providers have voiced that the law would impose such costly physical and staffing requirements that some clinics would be forced to close.

The issue has provoked an unusual running floor battle between two Republican senators - Bob Mensch, a former business executive from Montgomery County, and Pat Vance of Cumberland County, the legislature's only registered nurse.

Monday's 31-19 vote on the "study" amendment, proposed by Vance, was largely on party lines, but with notable Republican defections on sex and geographic lines. The measure picked up support of the majority of Republican women as well as several GOP senators from Southeastern Pennsylvania.

A final vote could come as early as Tuesday.

Vance, the lead sponsor of the original bill, said a study would shed light in the dispute over whether new requirements would shutter clinics. "Some say, 'Yes, it would shut them down'; others say, 'No, it won't,' " she said.

Mensch - who won passage last week of an amendment toughening the restrictions in Vance's original bill - said he was merely following the recommendations of the grand jury report last year that led to murder charges against Philadelphia abortion doctor Kermit Gosnell. That report - which said Gosnell's clinic had gone uninspected for 17 years - prompted calls for tougher scrutiny of abortion clinics.

Mensch's amendment would require clinics that perform abortions after nine weeks of pregnancy to meet the same standards as the nearly 300 "ambulatory surgical facilities" that perform outpatient operations. Those facilities have larger surgical rooms, wider, hospital-grade elevators, and a registered nurse on-site at all times.

Mensch's language would make Pennsylvania's abortion clinic regulations among the nation's most stringent. Ten states, including New Jersey, have similar laws - but they apply only to abortions later in pregnancy.

Mensch said during the Senate debate that there was no evidence clinics would be forced to close by such a law.

In 2009, two researchers who support abortion rights reached the opposite conclusion. They studied the effect of similar laws in two states and published their findings in the American Journal of Public Health.

In Texas, they found, the number of clinics offering abortions after 16 weeks of pregnancy dropped from 20 providers to none in 2004, when the law was imposed. By 2005, two clinics managed to come into compliance, with renovation costs estimated by one administrator at $750,000. By 2007, four clinics qualified as outpatient surgery centers; those clinics' fees increased $200 to $1,000 per procedure.

The researchers said Mississippi's only abortion clinic turned away more than 600 women seeking second-trimester abortions during the 18 months it took to comply with a 2005 law.

At Planned Parenthood of Southeastern Pennsylvania, president Dayle Steinberg oversees four clinics. Of those, she said, only the Northeast Philadelphia clinic could comply with the proposed new requirements because it is on a ground floor and needs no elevator.

Even there, Steinberg said, it would take an estimated two years and $1 million in construction to comply with the proposed new standards by turning four small operating rooms into one big one.

Both sides in the legislative debate have invoked the importance of women's health and safety. In urging the defeat of Vance's amendment, Mensch said the Gosnell grand jury report noted that most abortion clinics already "meet the highest level of care" and wouldn't have to make drastic changes.

Vance disagreed, telling colleagues, "If [the clinics] close down, women won't have health care."

Contact staff writer Amy Worden at 717-783-2584 or aworden@phillynews.com.