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.
If you are experiencing severe nausea and vomiting, and the above treatments do not appear to be helping, contact your doctor for further suggestions. 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: 1  Hyperemesis Gravidarum, which is a medical condition that causes you to lose essential nutrients needed during pregnancy. 2  Molar Pregnancy, which occurs when an abnormal growth of tissue develops within the uterus.