Based on insurance data and a government-sponsored study, academic researchers have concluded that those exceptions applied to only about 4 percent of an estimated 340,000 abortions performed in 2005. But that year, only one case of illegal abortion  which, on paper, is punishable by up to a year in prison for the woman and two for the doctor  went to court, according to data that prosecutors submitted to Parliament in October.

For decades, the South Korean government tended to look the other way, seeing a high birthrate as an impediment to economic growth. In the 1970s and 1980s, families with more than two children were denounced as unpatriotic, with official posters in South Korean villages driving the point home. Until the early 1990s, men could be exempted from mandatory army reserve duty if they had vasectomies.

Now, the government has concluded that this policy was too successful.

South Korea’s fertility rate, which stood at 4.5 children per woman in the 1970s, had fallen to 1.19 children by 2008, one of the lowest rates in the world. The government fears that the recent financial downturn may have depressed it further, and that the country’s rapidly aging population will undercut the economy’s viability.

In November, President Lee Myung-bak called for “bold” steps to increase the nation’s birthrate.

“Even if we don’t intend to hold anyone accountable for all those illegal abortions in the past, we must crack down on them from now on,” the minister for health, welfare and family affairs, Jeon Jae-hee, said.

But Ms. Jeon added that any crackdown should be coupled with an increase in medical fees for all doctors. The government cap on payments for medical services is thought to have encouraged doctors to perform off-the-books, and potentially far more lucrative, services like illegal abortions.

With fewer women having babies and the government holding down medical fees, many obstetrics clinics are struggling. Some obstetricians have switched to more lucrative skin care and obesity clinics. To those who remain, abortion  which usually costs about $340 and is paid for in cash up front because it is not covered by insurance  has become “a source of income we find really difficult to give up,” said Dr. Kang Byong-hee, an obstetrician in Paju, north of Seoul.

In addition to government policy and the economics of health care, social factors have contributed to the abortion rate. A bias for boys and against the disabled led to the widespread practice of aborting female fetuses or those with physiological defects, said Choi Sung-jae, a professor of social welfare at Seoul National University. A stigma against unmarried mothers, women’s increasing participation in the work force and the high cost of education are also seen as contributing to the trend.