Zhang Yufei, 42, left, his son Zhang Enlang, 13 months, his mother-in-law Li Zhihong and his wife Ma Yanyan, 30, pose for a photograph in their family home in Beijing, China on Nov. 20, 2013. After a relaxation in China's one-child policy, Zhang and his wife want a second child, but only after Beijing's heavily polluted air improves. (Simon Denyer/The Washington Post)

When 36-year-old Lois heard the news that China was relaxing its one-child policy, she was delighted and relieved. The Beijing mother had just discovered she was five weeks pregnant with her second child, a baby who would be illegal under existing law, and the alternatives were bleak. She had ruled out an abortion but faced the prospect of keeping the infant in hiding and not being able to send the child to school. If caught, she could face a fine of more than $50,000.

“When the policy change came out, my friends said it had happened just for me, just like a story you read in a novel,” Lois said in an interview, while her 6-year-daughter skipped and played with friends under an imposing statue of Mao Zedong in a park in Beijing.

But on Wednesday, five days after the announcement, the reality of China’s ­family-planning policy hit home. Lois read a newspaper article in which officials said that the law would not take effect immediately and that babies born before a yet-to-be-determined date would be illegal.

“If my baby is born just one day early, it is illegitimate,” she said. “It is ridiculous and unbelievable. I feel the unfairness of it, I feel desperation, I feel anger. I feel humiliated.”

The relaxation of the controversial one-child policy, which dates to 1980, is part of a sweeping package of economic and social reforms announced by Chinese President Xi Jinping.

Unveiled amid mounting concern about an aging population and a potential labor shortage, the new family-planning policy states that if either member of a couple is an only child, they may have two children. In the past, urban couples could have a second child if both of them were only children; rural couples could have a second if their first child was a girl.

The change will affect about 15 million to 20 million couples and push up the birthrate by about 1 million births a year, officials and experts say. But China’s overall population level will not be affected much and will still peak below 1.5 billion in about 20 years, from about 1.3 billion now, officials said.

Lois asked to be identified by her English name rather than her Chinese name, to avoid drawing the attention of authorities. The magazine writer is an only child, but her husband, a software engineer, is not. That means they could have only one child under existing rules.

Her daughter paused from her play to say how excited she was about getting a younger brother or sister. Lois said the girl was a very active participant in a discussion about baby names a few days ago, while her young friends had been thrilled to feel the mother’s tummy at the park Tuesday. Now, all the worries have come flooding back.

“My husband is very worried that the neighborhood committee would report us,” Lois said.

A maze of rigid rules

Penalties for parents who break the one-child laws are severe.

Yang Zhizhu, a former law professor at the China Youth University for Political Sciences, lost his job in 2010 and was fined $40,000 when his wife had a second daughter. Last year, he was allowed back but only to do research for a paltry salary of less than $1,000 a month. He is not allowed to lecture.

He has spent years researching the one-child policy. Like many experts, he said it has often been brutally enforced through forced sterilizations and abortions. The government has vastly overstated the policy’s benefits, he said, and the announced relaxation would do little to solve demographic problems. “It is like carrying a bundle of sticks to put out a fire,” he said.

The rules are so rigid that even those who comply with the official policy have to negotiate a bureaucratic maze run by officials with broad discretionary powers.

For example, if the law ­changes, Lois said she would have to return to her home province of Sichuan, as well as meet officials in Beijing, to verify that she is an only child. Her parents would be investigated to ensure they had not been divorced and had more children. Lois said she would probably need to obtain about 20 official stamps to complete the process.

Provinces will be able to set their own timetables to implement the changes. In places where population growth is high, local officials could decide to favor older couples and delay permission for younger couples to have a second child, said Wang Peian, vice minister of the national health and family planning commission. Critics say that arrangement would leave considerable discretionary power in the hands of local officials, leading to more corruption and abuse.

Mao Qunan, the commission’s spokesman, countered such concerns, saying in an interview that officials would “eliminate problems of corruption and brutal law enforcement.”

Financial constraints

Even after the policy is relaxed, not everyone affected will be rushing to have another child, especially given the rising costs of housing and schooling.

A survey on the Sina Weibo microblogging service this past week found that nearly 60 percent of participants would choose to have a second child but that nearly 30 percent would not. Another poll, by the Southern Metropolis Daily newspaper, found that 66 percent of people wanted two children, 9 percent wanted more than two and 21 percent wanted just one — mainly for financial reasons.

Among those reluctant to take the plunge are Xu Minhua, 28, and his wife, Miranda Yao, 33, who met while working for a German pharmaceutical company and had their first child last year. “Mostly it’s economic pressure,” Yao said.

With the couple’s parents living in the provinces and no day-care facilities nearby, they have hired a nanny to help look after their daughter. They also face heavy mortgage payments.

“If we had plenty of money, we might have another child,” Xu said, “but right now, we only have two rooms.”

Across the city, 42-year-old Zhang Yufei and his wife, Ma Yanyan, 30, have decided they can afford a second child and were very happy with the announced change in policy.

Zhang has a younger brother, but his wife is an only child. “If we have a second child, it will increase our family’s ability to sustain risk,” said Ma, sitting with her 13-month-old son in her arms. “We have heard a lot of stories of parents who have lost their only children.”

The couple also want a companion for their son. Nevertheless, they may wait a while.

“My son is breathing in more and more polluted air,” Zhang said. “The [Communist] Party told us the air will be better in five years, so maybe we will wait until then. Let’s trust them.”

When asked how he felt living under rules that gave officials so much power over his family arrangements, Zhang had a simple answer: “It’s absurd.”

Li Qi, Liu Liu and Guo Chen contributed to this report.