Earlier today, China finally stated it plans to reverse its one child only policy (and replace it with a two child policy), which had been in force since 1980 initially to curb extensive population growth. China was for many years the only country with a population greater than one billion, and even now India's population has reached the one billion mark, China is still the most populous country on Earth by a considerable margin of hundreds of millions.
36 years of having a strict and harshly enforced one child policy (even when relaxed in some circumstances) has had substantial and detrimental effects on China socio-economically and psychologically. Birth rates in China are well below the expected replacement level of 2.1, the rate needed to keep a population stable in the long-term. This is being exacerbated by the fact that China, like many wealthier nations in the Western hemisphere, now has a substantial elderly population with ~20% of its population being over the age of 65-China still has no free national healthcare system, and the elderly population will likely expand significantly over the next few decades. The gender imbalance, caused by numerous sex-selective abortions of female foetuses (since males are still valued more in Chinese society, especially in rural areas) is another serious problem with the one child policy, causing a serious imbalance of 117 males to every 100 females.
The fact that children are forced to grow up as only children as a result of government policy also often causes psychological harm, since having no siblings to relate to and knowing that they will be the one great hope their parents have places undue stress on them in a country that is harshly competitive, is intolerant of free speech, and where the consequences of failure are particularly dire.
On the other side of the argument, giving too many incentives for giving birth also causes serious long-term problems. Romania under Nicolae Ceausescu is a key example since the prohibition of birth control and strong encouragement to conceive many children meant that children parents could not or would not take care of were abandoned in grim and uncaring orphanages throughout Romania, especially when those children had disabilities or other birth defects; even though those orphanages have been closed down the consequences of over-encouraging population growth are still being felt today.
It is becoming clearer that over-consumption of resources, rather than total global population, is a key contributor to accelerating artificial climate change and increasing scarcity of important resources like fresh water. Using laws to restrict or overstimulate population growth for socio-economic or environmental purposes not only does not solve problems but can exacerbate them and cause problems of their own which can be very difficult to reverse. It is better that we focus on tackling overconsumption of resources and promoting sustainable and fair lifestyles, and given our current prosperity, our population will generally remain stable when we cease government interference (either pro-population growth or anti-population growth) with national or global birth rates, and have as fair a redistribution of wealth and resources as possible.