Okay, stupid, of those 7.03 children in 1800, how many of them died in childhood? Let me give you a hint. Abe and Mary Lincoln had three children.... only one of them lived to be an adult.The fertility rate of a country is the average number of children that women from that country will have throughout their reproductive years.
The birthrate in 1800 was 7.03 children per woman
The birthrate in 2020 was 1.78 children per woman
Infant mortality is minimal today- 6 per 1000 births. We are all better off for this. It also means women don't feel a need to pump out 6 babies hoping two of them might live long enough to become adults.