What is this passage mainly about? [originaltext] There are many reasons why

There are many reasons why family life in Britain has changed so much in the last fifty years. The liberation of women in the early part of the twentieth century and the social and economic effects of World War II had a great impact on traditional family life. Women became essential to industry and the professions. During the war they had worked in factories and proved their worth, now, with the loss of millions of men, their services were indispensable to the nation.
    More recently, great advances in scientific knowledge, and particularly in medicine, have had enormous social consequences. Children are better cared for and are far healthier. Infant death rate is low. Above all, parents can now plan the size of their family if they wish through more effective means of birth control.
    Different attitudes to religion, authority and tradition generally have also greatly contributed to changes in family life. But these developments have affected all aspects of society. It is particularly interesting to note that the concept of "the family" as a social unit has survived all these challenges.