Sharp rise in the number of paternity tests carried out in the capital has prompted concern among experts over the stress caused to children at the heart of disputes.

District courts and private clinics have seen a dramatic increase in the use of blood tests in divorce and custody cases in the past year. However, health experts warn that parents need to consider the extreme psychological strain they are putting on youngsters before demanding the screening.

"Divorce may be a relief to a couple who no longer love each other, but it's the child that bears the brunt of the dispute," said Wang Xingjuan, founder of Beijing Maple Women's Psychological Counseling Center, which has been providing social services to vulnerable women and children for 22 years.

"Paternity tests can severely impact a child's mental health, especially when the test result doesn't support the blood relationship between the child and the parent," she said.

Wang echoed a report on a recent study by Haidian district judge Chen Changyi that found the tests can have "long-lasting effects" on a child's confidence and ability to handle relationships.

In 2002, a teenager committed suicide by jumping out of a building in Daxing district after his 48-year-old father insisted on paternity test due to suspicions his wife was having an affair. The results came back as a match.

Haidian district court ordered paternity tests in 12 cases last year, double the number in 2005. Shijingshan district court ordered four (none two years ago), while Fengtai district court ordered five, up from two in 2009.

"Paternity tests are increasing year-on-year, mainly because of the custody and maintenance disputes over suspected illegitimate children," Wang Jianzhong, a judge at Fengtai's minor court, told China Daily.

He explained that the number of children being born to unmarried couples is on the rise, which is leading to court battles when they split up. More often than not, judges will suggest a paternity test before hearing the case.

Beijing men who have children with women without permanent residency - or hukou - in the capital are also fueling the spike, said Wang Jianzhong, as they need to prove the paternity to authorities before the child can be registered with the public security bureau.

Although most clinics offering paternity tests are exclusively reserved for the security or judicial departments, the capital has about eight private clinics that are open to the public, said Ma Kai, spokesman for Beijing Municipal Bureau of Justice, the supervising body.

Beijing Genomics Institute's center of forensic sciences, which is an authorized test clinic, received more than 5,000 applications last year, a year-on-year increase of 20 percent.

"People come here for many reasons," said center director Deng Yajun, who listed registering for hukou and court disputes as the top two. "Every year about 20 percent of the tests prove negative for a blood relationship."

Residents can apply for voluntary tests with just their identity cards and a photo. The cost is about 1,000 yuan.

In court cases, litigants can refuse to take the test "if they feel it's harmful to their health or goes against their child's best interests," added judge Wang Jianzhong. "The court can presume the parenthood if the other party has evidence that shows a high possibility they are the father."