Antibodies in blood?

5 years ago after my first born I had to get a blood transfusion. I am now 13 wks pregnant and with a routine blood test, my tests came back that I have developed antibodies called "big K." Due to the transfusion I had a few years back. I am a single mom, 24 years old with a 4 year old son. Has anybody else experienced this? I'm really concerned and I would like to know of any information anyone has. Thank you in advance!