India's 2011 census shows that the gender ratio of children younger than 6 has declined to 914 girls for every 1,000 boys as compared to 927 in 2001.
The decline in the number of girls is the steepest since India gained independence in 1947.
A blend of religious and cultural codes and economic reasons have led some to view the birth of a girl as a tragedy. While boys are seen as an asset to a family, girls are considered a burden that must be carried until they are married.
Before the technology to determine the child's sex was available, female babies were sometimes poisoned or smothered after birth. A 2006 study by The Lancet estimated that 10 million female fetuses had been aborted over the past 20 years. But experts now estimate that more than 1 million girls are killed in the womb every year.
"Female infanticide was more difficult because one would have to see the face of an innocent child. ... The new technology has eliminated that problem," said Jaya Bharti, head of the Divya Jyoti Jagrati Sansthan, a socio-spiritual organization based in Delhi.
Last week, Indian Prime Minister Manmohan Singh called female feticide and infanticide a "national shame."
Some parents especially dread the prospect of paying a heavy dowry, which includes money, gifts and property, at their daughter's marriage. The payment and acceptance of dowry is illegal in India, but it is still widely practiced.
Some families also see no benefit in having a girl since she is thought of as ultimately settling with her husband's family and so isn't regarded as worthy of inheriting property or carrying on the family name.
Earlier, sex selection was more widespread in educated and economically well-off families who had access to doctors with ultrasound machines. But now a growing number of people across different social and economic sectors have such access. These machines, once confined to big cities, are now available in smaller towns and urban villages where some doctors are willing to perform the sex-selective abortions for extra cash.
The desire to have fewer children also has contributed to the increase in female feticide. Previously, only the educated sections preferred a small family, but that desire has spread to other socio-economic classes. So now, instead of tolerating the girls while trying for a boy, some families choose to abort female fetuses.
A high mortality rate among girls up to age 5 is also contributing to the disproportionate sex ratio. "People don't provide health care to their daughters," said Meenakshi Ganguly, South Asia Director for Human Rights Watch.
Many activists want to see stronger implementation of the Pre-Natal Diagnostic Techniques (Regulation and Prevention of Misuse) Act of 1994, which makes sex selection illegal. The law imposes a prison sentence of three years and fines doctors and people who engage in the practice.
Population First, a Mumbai-based NGO, recently conducted a survey of 40 hospitals in a middle-class area of Mumbai, which found that 39 hospitals were in some sort of violation of the law.
Alamuru Lakshmi Sharada, program director of the NGO, said there are very few cases of doctors going to prison, and they often get away with only paying fines. In several instances, however, officials take bribes and don't pursue further action. "There is no bureaucratic will to implement the law," she said.
Sharada said the companies manufacturing the ultrasound machines need to assume the responsibility of keeping records of their clients.
"The aggressive marketing of the machines is not helping," she said, adding that sometimes a doctor gets one machine registered with the authorities but not the other.
But Ganguly stressed that the fight against abuse of the ultrasounds was tricky because activists did not want to restrict women's right to get an early abortion. "What we really don't want happening is taking away control over reproductive rights," she said.
For decades, education was seen as the best way to stop female feticide, but some activists are now questioning that approach since often it is educated families who engage in the practice.
Bharti said that the birth of a child is viewed as an investment, and this mindset can only be changed by promoting "human sensitivity" among people, through economic policies and public campaigns.
"Everything is connected to marketing and profitability," she said. "If the mindset is to kill the girl child, then no law can stop it."