Egg freezing has become a growing topic of discussion in China, where officials alarmed by the country’s first population decline in six decades are trying to boost the birth rate even as young people are increasingly putting off marriage and childbearing or avoiding it altogether.

But unmarried women are legally barred from undergoing the procedure in mainland China, prompting some to do it elsewhere at a much greater cost in a bid to extend their reproductive window.

Amid concerns that its working-age population is falling too quickly, China has made other moves aimed at increasing the birth rate. In 2016 it amended its decadeslong “one-child policy” to allow all couples to have a second child, and in 2021 the limit was raised to three.

But the policy shift has not increased the birth rate as expected, with young people citing the high cost of raising children, work stress and a reluctance to bring babies into a highly competitive society as reasons for their resistance to getting married and starting families. The country had a record-low fertility rate of 1.09 last year, state media reported in August.

Hong Kong, a Chinese territory, is a natural choice for many mainland Chinese women seeking to freeze their eggs because of its geographical proximity, shared language and high-quality health care.

Dr. Ng Hung Yu, a clinical professor at the Department of Obstetrics and Gynecology at the University of Hong Kong, said his hospital had received a growing number of egg-freezing inquiries since opening its services to single women from mainland China without any health issues.