The NY Times asks, is the current boomlet in fertility rates due to increased home ownership?
In the wide-open mortgage climate early this decade, creative loan products allowed more people than ever to buy homes, often a precursor to having children.
One factor, not mentioned in the article, could also be crucial. I read once that thin walls in apartment buildings were often a hindrance to couples having and enjoying sex. That problem goes away if you live in a house.