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.
For starters, USCIS will presume that if your marriage took place within a very short time of entry to the U.S. -- typically 90 days -- the purpose of the entry was to get married. No matter what, it's best to wait this long before the wedding.