Nearly half of Indian brides wed before they are 18-years-old, the legal age for marriage since 1978, a survey by the Lancet medical magazine says.
Carried out from a geographical and social cross-section of Indian society, the survey says that a total of 44.5% were married by the time they were 18.
It says that women who were child brides were far more at risk of having unwanted pregnancies.
Marriage at a young age carries grave health consequences, it says.
"Child marriage has serious consequences for national development, stunting education and vocational opportunities for a large sector of the population," says the paper, led by Anita Raj, a doctor at Boston University School of Public Health in Massachusetts, quoted by the AFP news agency.
Researchers collated data from a national family health survey that was carried out between 2005 to 2006 in India.
The survey involved 22,807 Indian women who were aged between 20 and 24 at the time of the survey.
India first introduced laws against child marriage in 1929 and set the legal age for marriage at 12 years. The legal age for marriage was increased to 18 in 1978.
Correspondents say that while the practice of child marriage has slowly diminished, it remains unacceptably high among rural, poor and less educated girls and and among those from central or eastern regions of the country who are more vulnerable to the practice.
The survey says:
The researchers say that existing policies and India's economic development gains have failed to help rural and poor populations eradicate child marriages.
They say that the reason why there are such high levels of sterilisation among young brides is because they have had their desired number of children at an earlier age.
But they say it was also indicative of inadequate fertility control, evident from the high numbers of unwanted pregnancies among the women.
They warned that sterilisation could reduce condom use in such couples, which would heighten the risk of HIV and other sexually transmitted infections.
Compared to a similar survey 10 years ago, the child bride proportion has fallen slightly but the Lancet report said the reduction was insufficient.