HONG KONG (Reuters) - A large proportion of women in India were married when they were still children, a study has found, and researchers warned that such unions carried higher risks of unwanted pregnancies and female sterilization.

Nearly all the women who were married before they reached the legal age of 18 reported that they used no contraception before they had their first child, according to the study, which was published in The Lancet.

UNICEF defines child marriage as marriage before 18 years of age and such a practice has been increasingly viewed as a violation of human rights.

Marriage at a very young age carries grave health consequences for both the girl and her children and it is well documented that adolescent mothers are more likely to experience complications such as obstetric fistula.

Researchers analyzed data from a national family health survey that was conducted from 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.

Of these, 22.6 percent were married before they were 16, 44.5 percent were married when they were between 16 and 17, and 2.6 percent were married before they turned 13.

“Women who were married as children remained significantly more likely to have had three or more childbirths, a repeat childbirth in less than 24 months, multiple unwanted pregnancies, pregnancy termination, and sterilization,” wrote the researchers, led by Anita Raj at the Boston University School of Public Health.

India 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 years in 1978.

While the practice of child marriage has decreased slowly, its prevalence remains unacceptably high, and rural, poor, less educated girls and those from central or eastern regions of the country were most vulnerable to the practice, the researchers wrote.

Such findings indicate that child marriage affects not only adolescents aged 16 to 17 years, but also large numbers of pubescent girls aged 14 to 15 years, and show that existing policies and economic development gains have failed to help rural and poor populations, the researchers wrote.

They attributed the high numbers of sterilization in young women married as children to them having their desired number of children at an earlier age.

But it was also indicative of inadequate fertility control, which was evident from the high numbers of unwanted pregnancies among these women.

They also warned that sterilization might reduce condom use in such couples, which would heighten the risk of HIV and other sexually transmitted infections.

Child-marriage prevention programmes should be broadened to include interventions for women married as children and men who might pursue children for marriage, the researchers added.