You are making the mistake of looking at single data points. Everything in life falls on a distribution. In science we try to represent the average likely hood of something. This does not mean that something bad will happen to everyone that has a bunch of kids, only that the likely hood of something happening is higher for that group then for a different group. Beyond this, it's an association, not an indication of cause.
So while it may not seem like it should be true. The data indicates that it is. We don't have to like it, we just have to explain the data.
Ok, got your point buddy.