No, this is exactly the opposite of true: you need to do more reading about the baby boom. It happened across many countries, including ones which had little involvement in WWII, and in almost all cases it began in the 1930s, even with the Great Depression underway. It got supercharged by the end of the war because that's when the economic doldrums finally ended, but upward trend in fertility predated even the beginning of the war, never mind the end.