Normally fetal fibronectin is present in cervicovaginal secretions before 21 weeks of gestation and after 37 weeks, but the concentration is normally low in the interval. The presence of increased levels of fetal fibronectin correlates with an increased risk for preterm delivery, often within 7 days of specimen collection.
Requirements for measuring fetal fibronectin to predict preterm delivery:
(1) The pregnancy should be between 24 weeks, 0 days and 34 weeks, 6 days of gestation.
(2) The membranes should be intact.
(3) There should not be significant bleeding.
(4) The specimen should be collected prior to manipulation of the cervix.
(5) Cervical dilation is minimal (< 3 cm).
NOTE: Revah et al emphasize that the test is more sensitive in symptomatic than in asymptomatic patients.
Parameters:
(1) fetal fibronectin concentration in cervicovaginal secretions
(2) cervical length
|
Parameter
|
Finding
|
Points
|
|
fetal fibronectin
|
< 50 ng/mL
|
0
|
|
|
>= 50 ng/mL
|
1
|
|
cervical length
|
> 25 mm (normal)
|
0
|
|
|
<= 25 mm (short)
|
1
|
number of risk factors =
= SUM(points for the 2 parameters)
Interpretation:
• minimum number of risk factors: 0
• maximum number of risk factors: 2
|
Number of Risk Factors
|
Risk of Spontaneous Preterm Delivery
|
|
0
|
low
|
|
1
|
intermediate
|
|
2
|
high
|
