To my knowledge it contributed very little.

Germany had a high population before World War 2, almost 69 million people in 1939. This is the population for Germany itself, not the annexed Austrian/Czech/Polish lands. By 1946, the population had shrunk to around 64 million people. That number accounts for about 6 million causalities, 4 million displaced Germans moving back to Germany, territorial losses, and births. By 1950 another 7 million POW's and displaced people returned to East and West Germany.

Since that time Germany's population has been on pace with other European nations, though the birth rate of native Germans is below the replacement rate since at least the 1990's. Immigration has made up a large part of Germany's population growth, and today almost 10 million people living in Germany are foreign born, accounting for over 10% of it's population.