This is very true Jan. A member of my family was born in February 1945 and was adopted into the family, having been put in an orphanage by his birth mother.
When he was adult, he applied for his adoption papers which gave the name of his birth mother. He found that she had died, but that he had half-brothers and half-sisters, but none of them had any information about his natural father, other than that he was American and died some months before he was born in France. He must be one of thousands of children born at that time, whose fathers went off to war and never returned; and with the death of his birth mother, any possible chance of finding more about his paternity was totally lost.
As ScouseBoy says, attitudes towards unmarried mothers were so different in those days, and without a supportive family, it was almost impossible for a woman to keep her child. Most gave them up for adoption in the hope of a better life for them with a new family, which must have been heart-breaking.