I am so sorry. Did you have ultra sounds and all the tests to see if there was any abnormalities up until that point? i was 14 weeks along when my ultrasound and my blood work began to show major problems. I do know that for me they told me I could possibly hold on to the baby all the way to eight months or more because it still had a healthy heart beat somehow. the ultra sound did show that there was no way the baby could develop and thrive further though. I can't imagine how hard that is for you, feeling like after that long everything must be going ok. I am sorry I can not help you more, but will let you know if I find anything to help.
Have you been checked for blood clotting problems?? If not, get the tests done. I was diagnosed with a genetic mutation called MTHFR. It causes bloodclots, and it keeps the body from absorbing folic acid, which the baby obviously must have. Most of the time, when a baby dies after the 1st trimester, research has showed it was caused by a bloodclot. I've met several woman on Med Help that had this happen. If your prone to bloodclots, and one forms in the umbilical cord, the baby will immediately die.
I am SO SORRY for what you're going thru. I'm going thru a "mishap" right now. On Mon morning I'm going in for a D&E for my 3rd m/c in 1 year. My new DR's finally did the right tests and figured out why I was miscarrying. If you're up to getting an autopsy done on your baby, your DR's should be able to tell you why you lost your lil one. My girlfriend lost hers at 22wks, but she didn't want her baby poked an probed so she didn't find out the cause, but she's pretty sure it was a bloodclot.
I will be praying for you.