Untreated, the clots cause organ damage and low red blood cell and platelet counts.
Doctors believe Ms Meredith's condition was triggered by an autoimmune response to pregnancy.
She was diagnosed with TTP four days after her condition deteriorated and she was rushed by ambulance to Queen Elizabeth Hospital in Birmingham.
"It escalated so quickly," she said.
"As soon as I got to A&E there was a doctor waiting for me, so I knew it was serious."
She received more than 27 bags of fresh frozen plasma to help stabilise her.
Plasma makes up 55% of a person's blood and contains antibodies, which strengthen or stabilise the immune system.
"I remember getting a leaflet and it said without plasma exchange there is a 90% mortality rate from an acute TTP episode," she said.
Paula Costin, from Shrewsbury, also said she knew first hand how important these therapies were.
She has blood cancers myeloma and non-Hodgkin lymphoma, which have in turn worsened another condition, called hypogammaglobulinemia, which is a low antibody count.
She said immunoglobulin had given her the chance to try and be more active and "live a little", after years of being careful due to her illnesses.
