What Causes Miscarriage During Pregnancy Achieved Through IVF?

41 year old female. I recently went thru donor ivf and became pregnant. at 4 weeks pregnant I noticed swollen lymph node in groin area on rt side. Dr. rec to monitor 8/26. Following weekend developed cough w/o chest congestion, 8/30 saw Dr. for cough and fever temp 100.3 treated w/ tylenol. 8/31 fever at night took tylenol, cough started took half benadryl, shower to ease cough. After shower chills, shivering, bleeding started n went to ER. temp 101.5, whiteblood cell 22000, sonogram showed 2 fetus one w/ hr 77, contractions pain and miscarried shortly after discharge. Lymph node still swollen. Treated at ER w/ iv antibiotics. No diagnosis. Is the cause of miscstriage or symptom of my body rejecting the pregnancy?