The kidney is not one large filter. Each kidney is made up of about a million filtering units called nephrons. Each nephron filters a small amount of blood. The nephron includes a filter, called the glomerulus, and a tubule. The nephrons work through a two-step process.
Generally speaking, first babies tend to engage from about 34 weeks to 36 weeks. However, some babies only engage once labour starts. Try not to worry, though. Even if your baby hasn't engaged by the time labour starts, in most cases, it's not a problem.
So then what is the solution to the engagement question? In my experience as a wedding producer, a six month to nine month engagement period tend to be the most successful, and least stressful, for all parties involved. Unless you have your heart set on a particular wedding date a year away, you and your fiancÃ© should not fret about setting a date less than nine months away.