The phrase "sidewalk cracks" refers to the small gaps or splits that can be found on the pavement where people walk on the side of the road. Full definition
Therefore, the erroneous conclusions is that sidewalk cracks cause babies to be born! (fieryfoodscentral.com)
They're so powerful they're able to thrive despite the most adverse conditions, growing out of stone walls, between sidewalk cracks and in near freezing or low moisture conditions. (stylenectar.com)