These baby universes are so small that one would not notice them joining on, or branching off. However, by joining on, they will alter the apparent values of quantities, like the electric charge on a particle. Thus, we will not be able to predict what the apparent values of these quantities will be, because we don't know how many baby universes are waiting out there. There could be a population explosion of baby universes. However, unlike the human case, there seem to be no limitting factors, such as, food supply, or standing room.
Baby universes exist in a realm of their own.
For most quantities, baby universes seem to introduce a definite, although fairly small, amount of uncertainty in the predicted values. However, they may provide an explanation of the observed value of one very important quantity, the so-called cosmological constant. This is a quantity that would give the universe, an in-built tendency to expand, or contract. On general grounds, one might expect it to be very large. Yet we can observe, how the expansion of the universe is varying with time, and determine that the cosmological constant is very small.