The UN has revised down its population projections largely because birth rates are falling faster than expected in some developing countries.
UN estimates are now that the global population will be about 9.7 billion in 2050, and around 10.9 billion in 2100. Beyond 2050/60 population will be falling in most regions except Africa where it will continue to increase. Indeed most of the net population growth in this century will be in Africa as health care improves, even as the fertility rate gradually falls to ~2.1. Global population growth is projected to fall to zero sometime around 2100.
Meanwhile, the UN estimates that a 15 year old boy alive today in Bangladesh has higher chance of living to 50 than a similar boy in the USA. I understand that this is not necessarily to do with the excellent standard of health care in Bangladesh; rather, it's because of the propensity of the US health sector to push people into killing themselves with opioids. Not even the most fanatical population-reduction campaigners dared to dream that strategy up.