Beijing ? China has 32 million more young men than young women — a gender gap that could lead to increasing crime — because parents facing strict birth limits abort female fetuses to have a son, a study released Friday said.

The imbalance is expected to steadily worsen among people of childbearing age over the next two decades and could trigger a slew of social problems, including a possible spike in crime by young men unable to find female partners, said an author of the report published in the BMJ, formerly known as the British Medical Journal.

“If you’ve got highly sexed young men, there is a concern that they will all get together and, with high levels of testosterone, there may be a real risk, that they will go out and commit crimes,” said Therese Hesketh, a lecturer at the Centre for International Health and Development at University College London. She did not specify what kinds of crimes.

The study said analysis of China’s 2005 census data extrapolated that males under age 20 exceeded their female counterparts by a whopping 32 million.

The study found that China has 119 male births for every 100 girls, compared with 107 to 100 for industrialized countries.

“Nothing can be done now to prevent this imminent generation of excess men,” said the report by Hesketh and two professors from eastern China’s Zhejiang province.

The study found that the biggest boy-girl gaps are in the 1 to 4-year-old group — meaning that China will have to grapple with the effects of that imbalance when those children reach reproductive age in 15 to 20 years.

China imposed strict birth controls in the 1970s to limit growth of its huge population, noting that resources, especially land, were increasingly strained and that changes were needed in its new push to modernize. The government says the controls have prevented an additional 400 million births in the world’s most populous country of 1.3 billion.

But families, especially rural ones, cling to traditional preferences for a male heir, and infanticide of baby girls became a problem. In response, some parts of China allow couples to have a second child if the first is a girl.

The prevalence of sonograms in recent years has allowed parents to learn the gender of their fetus about 20 weeks into pregnancy, Hesketh said, leading to a rise in abortions based on sex. Abortion is legal and widely available.

China bans tests to determine the fetus’ gender for non-medical reasons but they are still commonly done, mainly by underground private clinics in the countryside.

Many countries ban abortion after 12 or sometimes 24 weeks of pregnancy unless the mother’s life is at risk. China’s laws do not expressly prohibit or even define late-term termination.