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.
After an unprotected sex, how long will it take till you know you are pregnant? You are most likely to get pregnant if you had sex around the time of your ovulation. This is when you are fertile because an egg has just been released. This happens about two weeks from the first day of your last menstruation.