Some doctors' families in India are having more sons than daughters, a new study in the U.S. journal Demography claims, implying that they, too, may be using illegal sex-selective practices that are thought to be widespread in the country.

Female feticide among not only poorer and uneducated families but also India's burgeoning urban middle class has contributed to the nation's skewed sex ratio, researchers say. In the past decade, the number of girls younger than 6 fell from 927 for every 1,000 boys to 914, national census data for 2001 and 2011 show.

In 1996, the government banned the use of ultrasounds to determine the sex of an unborn child unless a medical emergency requires such knowledge. But the new study, titled "Skewed Sex Ratios in India: Physician, Heal Thyself," suggests that doctors may be accessing the technology to prevent the births of girls in their own families.