Americans had the lowest number of babies in more than four decades during 2020, mirroring a slump in European birth rates, as the Covid-19 pandemic forced more people to take care of sick family members or deal with job losses. Birth rate in the United States fell 4 percent in 2020 to about 3.6 million babies, the sixth straight annual decline and the lowest since 1979, according to the U.S. Centers for Disease Control and Prevention.