Could Lovenox Be Stopped Before The Diagnosis Of The Cause For Vein And Arterial Clot?

My newborn was born 4 weeks early with a completely blocked aorta and right and left illiac arteries. There blod clots were found on day three of his life along with a venous clot in the left part of his brain. We are followed at CHOP. All of his genetic tests have come back normal for clotting factors. As have mine. Every blood test they have given him for proteinlevel etc has been normal, collagen testing of blood is also normal. He is treated with lovenox injections 2 times a day. No one can seem to figure out why this happened or if he is at risk for more clots if taken off the lovenox. He is now 10 months old, all of his clots have blood flow thorugh them and are nearly resloved. He is growing normally with a slighly swollen right foot i cm larger on right side that left. The plan is to give him another MRV and doppler ultrasound next week to determine if lovenox should be stopped. How can they stop this drug if we don;t know what caused a venius and artieral clot? Can you tell me who is the top pediatric hemetologist in the country? Have you ever seen this before in your practice? Any thoughts or suggestions for me to pass along to our CHOP physicians?