Question

What happened to the number of births in the two years prior to 1946

Answer 1

The Baby Boom period.

The Baby Boom period meant a significant increase of birth rate.

The people born during this period are known as "baby boomers". This period occurred in the middle of the 20th century, beginning in the late 1930s and ending in the 1960s. The baby boom occurred in countries that went  through enormous damage from the war and economic hardships. Some of those countries were Germany and Poland, for example. In the case of the United States, the baby boom was attributed to the number of veterans that returned home after the war ended in 1945.

Answer 2

It's called baby boom when the United States birth rate was to high