Fragile X and now something else???

Hello, I am currently 25 weeks and I will be 26 tomorrow so I went to my doctors appointment this morning to just have a regular visit. I am a carrier for Fragile X and have known for a while but I am in the intermediate group so chances of passing it on to my son is pretty low. My doctor is a very serious man (straight facts not really a caring doctor) and he tells me every time I go that even though my chances are low we are still going to take many precautions. Today he told me that in my second round of testing there was a certain hormone that I was not on a good level for which can possibly lead to pre term labor, still birth, and other complications. Does anybody know what that could be? I did not get to hear what he said the hormone was so I do not know if he was just going into more detail of this just being something that happens to carriers of the fragile X syndrome or if I do have another problem that I could not understand. If anyone has any advice please let me know I have tried doing research but I can not find anything. :(