<unk>  <unk>  is a protein produced by fetal cells and a type of<unk> .<unk>  is found at the interface of the chorion and the decidua (between the fetal sack and the uterine lining).
It can be thought of as an adhesive or "biological glue" that binds the fetal sack to the uterine lining.  It is an excellent biological marker of premature (preterm) delivery; a delivery before 37 weeks of gestation.<unk>  "leaks" into the vagina if a preterm delivery is likely to occur and can be measured in a diagnostic test.  When the<unk>  test is considered positive, delivery is likely to occur soon.  When the<unk>  test is negative, it means that there is little if any danger of preterm labour for 7-10 days.  The test is easily performed.  A specimen is collected from the patient using a vaginal swab.  The swab is placed in a transport tube and sent to the lab for testing.  The lab can easily produce a test result in less than one hour.
A systematic review of the medical literature found that<unk>  is a good predictor of spontaneous preterm birth before cervical dilation. The test may be run on patients between 22 and 35 weeks gestation.
Fetal fibronectin
Carrier protein
Cardiolipin
Fetal hemoglobin
Icterogenin
Thrombus precursor protein 
Antihemophilic factor 
Antihemophilic factor