It is indeed quite a stretch to see how this could affect world population in the next few years, but I have read about people going through crazier developments over the course of a lifetime.
One example scenario would require some narcissistic billionaire women to start producing their personal cloning machines. Production could go up to, say, an extra one of them (except for the billionaire part) each year. If that catches on, in a similar fashion to plastic surgery, we could see global fertility rates revert to Catholic levels. It also helps to think in terms of identical twins, triplets, and beyond.
Having a lot of children is now mostly limited by raising of said kids to require a lot of effort and money. It does not seem like a stretch to assume that robots could lend a hand here, at least on the 75 year horizon.