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.
How quickly after unprotected sex can you get pregnant? Generally, it takes 3 days for sperm to get to the egg, fertilize it. A further few more days for the egg to embed it self into the lining of the womb. Even if you had sex 5 or 10 times in the same day, the male body can create enough sperm to get you pregnant.