"This bill does take it one step further," said Sen. Chuck Winder, R-Boise, who sponsored the legislation on behalf of the anti-abortion group Right to Life of Idaho. "I would think the most basic human right we have to protect is the right to life."
Foes likened the measure, Senate Bill 1387, to George Orwell's dystopian novel, "1984."
"Senate Bill 1387 wants to say, the state knows better," said Sen. Les Bock, D-Garden City. "This is just another version of Big Brother."
Idaho's measure, similar to existing Texas and Virginia laws that have provoked heated debate in those states, requires a doctor performing an abortion or prescribing medication to terminate a pregnancy to conduct a fetal ultrasound.
The woman would have the option of viewing an image of the fetus and listening to its heartbeat.
The measure would also require Idaho's Department of Health and Welfare to make available a list of places in Idaho, typically anti-abortion health care centers, where those considering an abortion could get a free ultrasound.
Still, those women would have to submit to a second ultrasound should they opt for an abortion, according to the measure.
Opponents blasted the bill because it includes no provisions to exempt women or their doctors from the requirement in instances of a medical emergency or when the woman seeking an abortion had been the victim of rape or incest.
Sen. Shawn Keough of Sandpoint, one of the five GOP senators to vote against the bill, said she was a "right-to-life" lawmaker, but couldn't support the encroachment of government into the privacy of the doctor's practice.
"What place do we as a government have in that room with that patient and with that doctor?" Keough said. "I ask you to think with your head and your heart and turn this legislation back."
The other Republicans who voted against the bill were Joyce Broadsword, of Sagle; Jim Hammond and John Goedde, of Coeur d'Alene; and Tim Corder, of Mountain Home.
Last year, Idaho Republicans passed a measure to prohibit abortions after the fetus had reached 20 weeks of gestation.
Sponsors of this latest bill said they hope that by anchoring the ultrasound mandate in state law, it will help convince women torn over the decision to end their pregnancy to carry their fetus to full term.
They contend that a woman who sees an image of her fetus and hears its heartbeat will be less likely to proceed with an abortion.
"I am pleased to do whatever I can to protect innocent human life," said Sen. Steve Vick, R-Dalton Gardens.
For foes of the bill, however, it went too far, in part because it includes the likelihood that a woman early in her pregnancy would be forced to undergo an invasive, state-mandated vaginal ultrasound.
Though Winder had removed a provision requiring a vaginal ultrasound in favor of allowing the doctor and woman to decide what was most appropriate, the Senate's one medical doctor, Jeff Schmidt, D-Moscow, said a vaginal ultrasound would likely be required because it's considered by medical professionals to be the most effective means of detecting a fetal heartbeat before 10 weeks.