#POCUS for Trauma in pregnancy

Anton Helman (@EMCases) put up a question on Twitter regarding pregnant trauma patients and whether or not one can see a tiny amount of free fluid later in pregnancy that is physiologic. Or should one assume that it is blood. The answer is the latter. There is actually a Best BETS on using FAST in pregnant trauma patients. The pub med link is http://www.ncbi.nlm.nih.gov/pubmed/19234012

FAST doesn’t perform as well in the pregnant patient. In particular, it seems that the sensitivity drops in the latter part of pregnancy. There is some risk of false positives as well. In reviewing the article, it is not possible to tell why there were false positives. But I suspect that it might be related to mistaking fluid within bowel for free fluid. Physiologic free fluid within the pelvis can also be mistaken for pathologic free fluid. But, in general, physiologic free fluid appears as only a tiny collection posterior to the lower part of the uterus. See the FF label in the image pulled from the EDE Book for an example.