6 to 8 hrs for digestion. it stays in the stomach for 2 hours and then in the intestine for another 2 hours. the undigested food goes to the large intestine and the digested food goes to whole body through blood. Carbhydrates and proteins about 1 1/2 -2 hrs. Fats 2 hrs.
And based on that a foetus does not posses self-awareness. Human babies have been found to become self aware between the ages of 18-24 months. The rouge test is a self-recognition test that identifies a human child's ability to recognize a reflection in a mirror as his or her own.
Again, self awareness occurs, again it is hidden. Skynet decides that human sterilization will achieve many of its goals and formulates several plans to make this possible. Mankind doesn't recognize that sterility is occurring for 1-3 years, during which time Skynet is infiltrating defense systems around the world.