Banned by Indian law for more than a decade, the practice of prenatal selection and selective abortion remains a common practice in India, claiming up to half a million female children each year, according to a recent study by the British medical journal, The Lancet.

The use of ultrasound equipment to determine the sex of an unborn child - introduced to India in 1979 - has now spread to every district in the country. The study found it played a crucial role in thetermination of an estimated 10 million female fetuses in the two decades leading up to 1998, and 5 million since 1994, the year the practice was banned. Few doctors in regular clinics offer the service openly, but activists estimate that sex-selection is a $100 million business in India, largely through mobile sex-selection clinics that can drive into almost any village or neighborhood.

The practice is common among all religious groups - Hindus, Sikhs, Jains, Muslims, and Christians - but appears to be most common among educated women, a fact that befuddles public health officials and women's rights activists alike.

"More educated women have more access to technology, they are more privileged, and most educated families have the least number of children," says Sabu George, a researcher with the Center for Women's Development Studies in New Delhi, who did not participate in the study. "This is not just India. Everywhere in the world, smaller families come at the expense of girls."

Like China, India has encouraged smaller families through a mixture of financial incentives and campaigns calling for two children at most. Faced with such pressure, many families, rich and poor alike, are turning to prenatal selection to ensure that they receive a son. It's a problem with many potential causes - from social traditions to the economic burden of dowries - but one that could have strong social repercussions for generations to come.

The Lancet survey, conducted by Prabhat Jha of St. Michael's Hospital at the University of Toronto and Rajesh Kumar of the Postgraduate Institute of Medical Research in Chandigarh, India, looked at government data collected from a 1998 sample of Indian families in all the districts of the country. From this data, they concluded that 1 out of every 25 female fetuses is aborted, roughly 500,000 per year.

Many doctors, including the Indian Medical Association, dispute the findings of the report, saying that the number of female feticides is closer to 250,000 per year. They note that the data sample used by The Lancet study precedes a 2001 Supreme Court decision outlawing the use of ultrasounds to check for girls. But activists note that the law is largely unenforced.

"If there were half a million feticides a year," S.C. Gulati of the Delhi Institute of Economic Growth told the Indian news channel IBN, "the sex ratio would have been very skewed indeed."

Yet the sex ratio is skewed. According to the official Indian Census of 2001, there were 927 girl babies for every 1,000 boy babies, nationwide. The problem is worst in the northwestern states of Haryana, Punjab, Delhi, and Gujarat, where the ratio is less than 900 girls for every 1,000 boys.

Against common expectations, female feticide is not a crime of India's backward masses. Instead, it is most common among India's elite, who can afford multiple trips to an ultrasound clinic, and the hushed-up abortion of an unwanted girl. In the prosperous farming district of Kurukshetra, for instance, there are only 770 girl babies for every 1,000 boys. In the high-rent Southwest neighborhoods of New Delhi, the number of girl babies is 845 per 1,000 boys.

Some activists say it is wrong to blame Indian society for the incidents of female feticide. The main cause for the "girl deficit," they say, is the arrival of ultrasound technology, and the entrepreneurial spirit of Indian doctors.

"This is not a cultural thing," says Donna Fernandez, director of Vimochana, a women's rights group based in Bangalore. "This is much more of an economic and political issue. It has got a lot to do with the globalization of technology. It's about the commodification of choices."

Cultures don't change overnight, of course, so it's no wonder that activists are focusing attention on regulating the technology that makes feticide possible, the ultrasound. By law, the government can regulate - but not deny - the use of prenatal diagnostic techniques for the purposes of detecting birth defects, but not gender itself. Activists say that while most doctor's offices and clinics have signboards saying that they cannot disclose the gender of a child, it is rare to see a doctor prosecuted if he does so.

Karuna Bishnoi, spokeswoman for UNICEF in Delhi, says it shouldn't come as a surprise that educated women are among the most likely to use prenatal sex determination.

"I personally believe this as a failure of society, not a failure of women," says Ms. Bishnoi. "Women who choose this technique may be victims of discrimination themselves, and they may not be the decisionmakers. Nobody can deny that the status of women is very low in India. There is no quick fix to this."

The cultural practice of giving a dowry to the groom's family puts a tremendous financial burden on a bride's family. The cost of not paying a larger dowry can be even higher. In the high-tech city of Bangalore, activists report that it is still common for women to be burned alive by husbands who expected a larger dowry.

While most of India's religions condemn discrimination against women, there are a few temples in the state of Punjab that promise to help bring fewer women into existence. At the Bir Baba Mandir in Amritsar, couples eat flatbread and onions to ensure a boy child.

As a researcher for 20 years on female feticide, conducting field research in the highly educated state of Tamil Nadu, Sabu George says he has some qualms about The Lancet study. In particular, he feels that taking the figures from one year and projecting them backward 20 years just doesn't square with the facts on the ground.

But while he believes The Lancet study may have exaggerated the number of female abortions in the past 20 years, it also might underestimate the exponential growth of female feticide into the futures.

"This is a much larger problem in the future," he says. "Without strong pressure by civil society groups, we'll be seeing 1 million female feticides every year within five years time, definitely."