Very simple , look at this video you will get it.
Birth control: a rule, not a pill China’s two-child policy is having unintended consequences Reluctant to pay for multiple maternity leaves, companies are choosing not to hire young women
THE one-child-per-couple policy was horrific for women in China. Many were subjected to forced sterilisations or abortions. Newborn girls were killed, removed by family-planning officials or abandoned by parents desperate that their one permitted baby be a boy. Women from neighbouring countries suffered, too, as victims of human trafficking; a skewed sex-ratio made it more difficult for young men to find Chinese wives. So the government’s announcement in late 2015 that it was relaxing the policy, after 35 years, was good news. Yet the two-child-per-couple policy that replaced it may bring different kinds of problems. source https://www.economist.com/china/2018/07/26/chinas-two-child-policy-is-having-unintended-consequences
For a generation the government assured women that “one is enough” and that “late marriage and late childbirth are worthy.” Now state media urge them to marry while still in university and remind them that older mothers are more likely to have babies with birth defects, notes Leta Hong Fincher, an author and academic. Officials are encouraging childbirth because they worry that the fertility rate (the number of children a woman can expect to have during her lifetime) has sunk well below 2.1, the level required to keep the population stable in the long term. They fear a shrinking population will hamper economic growth.