T cells, which are one type of white blood cell in the immune system, somehow become sensitized to proteins in the CNS. When T cells become activated, they enter the CNS through blood vessels and produce damaging inflammation.
1 Fatigue or Tiredness: Feeling fatigued or more tired than usual, is a pregnancy symptom which can also start as early as the first week after conception.  Morning Sickness or Nausea: This well-known pregnancy symptom will oftentimes show up between 2-8 weeks after conception.
While nausea during pregnancy can be normal, it can also point to a problem that needs to be addressed. Examples of potential conditions seen with severe nausea are: Hyperemesis Gravidarum, which is a medical condition that causes you to lose essential nutrients needed during pregnancy.