How come no couples in the film have children.

Even the couple at the Cox party at the beginning of the film didn't have children.
When Harry mentioned that his wife wrote children's books, the woman said that her neices and nephews loved them, which seems to imply (in my opinion) that they don't have children themselves.
Most of the people in the film also seem to be middle-aged people already, so they probably won't be having any children in the future.

Perhaps they don't have children because they are simply in uphappy relationships.
Would this mean that the couple at the Cox party were likely to have an unhappy relationship too?
Linda and Ted also don't have children because they have relationship problems in their life i.e. the absence of an intimate relationship

Or are they trying to say something about government jobs and children.
Or perhaps government jobs and unhappy marriages.
Or perhaps unhappy marriages being linked to both people in the marriage having careers.
Or perhaps they were more specifically trying to say something about the women in the film seeing as both Mrs Cox and Mrs Pfarrer have jobs involving children. Perhaps there is a connection here.

Or perhaps children were simply not suitable for a dark movie like this and Im looking too much into such a small detail.
I don't think that I am though, because they easily could have had the woman at the Cox party say that her children loved the books rather than her neices and nephews. This implication in the dialogue seemed deliberate to me.

Anyone have any ideas?