A nurse at a hospital in Xiangyang, Hubei province, helps Chen Jing to breast-feed her second child on Friday. Gong Bo / for China Daily

Yuan Xin said this trend is declining, particularly among women younger than 35.

To enable women to make informed choices about contraception, the central government has scrapped hukou barriers.

The amendment to the law states that a woman's choice of contraception must be respected. But it still recommends long-term methods for women who already have two children.

According to government estimates, 90 million women will become eligible to have a second child under the new policy.

About 80 percent of them are estimated to have had IUDs implanted or to have undergone tubal ligation, Yuan said.

China has about 270 million married women of childbearing age.

According to the National Health and Family Planning Commission, among the babies born last year, the number of first children dropped by 850,000 year-on-year, or by 4.1 percent. The number of second children born rose by 450,000.

To meet demand, many maternity hospitals began to set up second-child consultancy offices to help couples with professional advice.

Mei Li, an obstetrician-gynecologist at a district maternity hospital in Guangzhou, Guangdong province, said couples have been asking about the free operations to reverse long-term contraceptive procedures.

Starting in November, more women began seeking the procedures and 293 IUD removals were performed in December alone, a year-on-year increase of 51 percent, Mei said.

An IUD removal procedure normally takes between three and five minutes and costs several hundred yuan, with medical checkups required beforehand.

Mei dismissed as "a misunderstanding" the notion that IUDs can harm a woman's health. "It's been proven worldwide that they are safe and effective, and the services available at qualified hospitals are of a high standard," she said.

In contrast, aborting an unwanted pregnancy risks major problems arising such as menstrual irregularity, abdominal pain or infertility.