Fetal fibronectin testing for reducing the risk of preterm birth
Abstract
Background
Fetal fibronectin (FFN) is an extracellular matrix glycoprotein localized at the maternal‐fetal interface of the amniotic membranes, between chorion and decidua, where it is concentrated in this area between decidua and trophoblast. In normal conditions, FFN is found at very low levels in cervico‐vaginal secretions. Levels greater than or equal to 50 ng/mL at or after 22 weeks have been associated with an increased risk of spontaneous preterm birth. In fact, FFN is one of the best predictors of preterm birth in all populations studied so far, and can help selecting which women are at significant risk for preterm birth.
Objectives
To assess the effectiveness of management based on knowledge of FFN testing results for preventing preterm birth.
Search methods
We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (January 2008), MEDLINE (1966 to December 2007) and all references in identified articles.
Selection criteria
Randomized controlled trials of pregnant women between the gestational ages of 22 and 34 weeks screened with FFN for risk of preterm birth. Studies included are based exclusively on knowledge of FFN results versus no such knowledge, and we have excluded studies including women with only positive or only negative FFN results.
Data collection and analysis
All four authors assessed studies for inclusion and quality and extracted data.
Main results
We identified 13 trials, of which five were eligible for inclusion. The five included studies randomized 474 women, of which 235 were randomized to knowledge and 249 to no knowledge of FFN.
Preterm birth less than 37 weeks was significantly decreased with management based on knowledge of FFN results (15.6%) versus controls without such knowledge (28.6%; risk ratio 0.54; 95% confidence interval 0.34 to 0.87). All other outcomes for which there were available data (preterm birth at less than 34, 32, or 28 weeks; gestational age at delivery; birthweight less than 2500 grams; perinatal death; maternal hospitalization; tocolysis; steroids for fetal lung maturity; and time to evaluate) were similar in the two groups. No other maternal or neonatal outcome was available for meaningful analysis.
Authors' conclusions
Although FFN is commonly used in labor and delivery units to help in the management of women with symptoms of preterm labor, currently there is not sufficient evidence to recommend its use. Since this review found an association between knowledge of FFN results and a lower incidence of preterm birth before 37 weeks, further research should be encouraged.
PICOs
Plain language summary
Fetal fibronectin testing for reducing the risk of preterm birth
Preterm birth before 37 weeks is the main cause of death and sickness for newborn infants. While most women have preterm labor symptoms such as contractions before having a preterm birth, most such women with symptoms deliver at term (greater than or equal to 37 weeks). Fetal fibronectin is a test that can identify the women with symptoms of preterm labor most at risk for preterm birth by measuring the level in secretions from the vagina and/or cervix. This review of five controlled studies that randomised 474 pregnant women did not find enough evidence to support or refute the use of the fetal fibronectin test for the management of women with symptoms of preterm labor. Further research should be encouraged.
