Today, it is too expensive to have children. There are big costs for child care, education, clothing and food. These costs only rise. More and more people are making the decision that they cannot afford to have a child and give the child everything that she needs to be successful in life. It's just economic reality.
If a woman doesn't earn enough, whether she is in a relationship or not, then I doubt she will want to have children. Children need a whole lot of basic necessities none of which are cheap. I'm not surprised more women are choosing a childless future as it truly is pretty expensive and with the economy still recovering, it doesn't seem like the right time to have children.
With the crazy politics having everyone wondering whether Trump will flinch one day and blow Korea or another enemy off the map, it seems like a bad time to have children. Europe has already been suffering from a declining economy, so it is no wonder French women are putting off starting a family.
Women are bearing less children both in Europe and (to a lesser extent) the United States, but it is due to a shift in cultural values as opposed to economical reasons. More and more, there is an emphasis on individualism, particularly in the realm of women's rights. This is a good development, but has led to the drop in birth rates.