In my recent Cato paper, "All the President’s Mandates: Compulsory Health Insurance Is a Government Takeover," I explain that if Congress compels Americans to purchase health insurance, it would "inevitably and unnecessarily open a new front in the abortion debate, one where either side—and possibly both sides—could lose."
Slate's William Saletan explains how the pro-choice side could lose:
This week, the Senate finance committee is considering amendments that would bar coverage of abortions under federally subsidized health insurance. Pro-choice groups are up in arms. After all, says NARAL Pro-Choice America, "In the current insurance marketplace, private plans can choose whether to cover abortion care—and most do." If Congress enacts subsidies that exclude abortion, "women could lose coverage for abortion care, even if their private health-insurance plan already covers it!"...
The argument these groups make is perfectly logical: If you standardize health insurance through federal subsidies and coverage requirements, people might lose benefits they used to enjoy in the private sector. But that's more than an argument against excluding abortion. It's an argument against health care reform altogether.
Saletan also explains why pro-life and pro-choice positions on Obama's health plan are irreconcilable:
To get what they consider neutrality, pro-choicers have to make pro-lifers pay indirectly for abortions. And to keep what they consider clean hands, pro-lifers have to make abortion coverage federally unsupportable and therefore, in a subsidy-dependent system, commercially nonviable.
Rather than an argument against all health care reform, I'd say this is an argument against reforms that expand government subsidies or otherwise give government the power to choose what kind of insurance you purchase. Fortunately, there are better ways to reform health care.