It's natural to have children. We are programmed to do so. Those that can are fortunate. Those that can and have healthy children, even luckier. Yet there is no denying that having children is expensive for everyone. maternity and paternity costs. Unless you are fortunate to work with a highly profitable business it's likely that maternity/paternity will cost you personally. On returning to work you may request shorter flexible hours, more cost. The employer also faces costs. Cover while you are away, loss of production, training costs and uncertainty of dates of return and in what capacity. 

So imagine being an investor, a genuine conundrum if you only look at the short term. In the modern world the challenge of people being away on maternity, paternity, sabbaticals or sick leave means that employers and therefore investors have to take a longer term view and make contingency for the fact that humans are programmed to reproduce, will be sick and in the modern-day when it's predicted the working age will continue to extend, need longer periods of time off during their careers.