They are higher in less developed countries, but still falling.
Go to https://ourworldindata.org/fertility-rate and select some regions, see for yourself. Africa as a whole has declining fertility rates. Even if you look a high-growth countries such as Niger or Democratic Republic of Congo, the fertility rate has been declining in the last 20-30 years, and you'll be hard-pressed to find a country where it has gone up.
Go to https://ourworldindata.org/fertility-rate and select some regions, see for yourself. Africa as a whole has declining fertility rates. Even if you look a high-growth countries such as Niger or Democratic Republic of Congo, the fertility rate has been declining in the last 20-30 years, and you'll be hard-pressed to find a country where it has gone up.