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Quantitative fetal fibronectin to predict preterm birth in asymptomatic women at high risk

Research output: Contribution to journalArticlepeer-review

Danielle S Abbott, Natasha L Hezelgrave, Paul T Seed, Jane E Norman, Anna L David, Phillip R Bennett, Joanna C Girling, Manju Chandirimani, Sarah J Stock, Jenny Carter, Ruth Cate, James Kurtzman, Rachel M Tribe, Andrew H Shennan

Original languageEnglish
Pages (from-to)1168-1176
Number of pages9
JournalObstetrics and Gynecology
Issue number5
Early online date1 May 2015
Accepted/In press1 May 2015
E-pub ahead of print1 May 2015
Published1 May 2015

King's Authors


OBJECTIVE: To evaluate the diagnostic accuracy of cervicovaginal fluid quantitative fetal fibronectin, measured by a bedside analyzer, to predict spontaneous preterm birth before 34 weeks of gestation.

METHODS: We conducted a prospective masked observational cohort study of cervicovaginal fluid quantitative fetal fibronectin concentration in asymptomatic women at high risk of spontaneous preterm birth (n=1,448; 22-27 6/7 weeks of gestation) measured using a rapid bedside analyzer. The routine qualitative result (positive-negative) was made available to clinicians at the time of testing, but the quantitative result remained blinded until after delivery.

RESULTS: Spontaneous preterm birth (less than 34 weeks of gestation) increased from 2.7%, 11.0%, 14.9%, 33.9%, and 47.6% with increasing concentration of fetal fibronectin (less than 10, 10-49, 50-199, 200-499, and 500 ng/mL or greater, respectively). A threshold of 200 ng/mL had a positive predictive value of 37.7 (95% confidence interval [CI] 26.9-49.4) with specificity 96% (95% CI 95.3-97.3). Women with a fetal fibronectin concentration of less than 10 ng/mL had a very low risk of spontaneous preterm birth at less than 34 weeks of gestation (2.7%), no higher than the background spontaneous preterm birth rate of the general hospital population (3.3%). The quantitative fetal fibronectin test predicted birth at less than 34 weeks of gestation with an area under the curve (AUC) of 0.78 (95% CI 0.73-0.84) compared with the qualitative test AUC 0.68 (95% CI 0.63-0.73). Quantitative fetal fibronectin discriminated risk of spontaneous preterm birth at less than 34 weeks of gestation among women with a short cervix (less than 25 mm); 9.5% delivered prematurely less than 10 ng/mL compared with 55.1% greater than 200 ng/mL (P<.001).

DISCUSSION: Alternative risk thresholds (less than 10 ng/mL and greater than 200 ng/mL) improve accuracy when using quantitative fetal fibronectin measurements to define risk of spontaneous preterm birth. This is particularly relevant for asymptomatic women with a short cervix.


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