Jolande Y. Vis

Objective We assessed the influence of external factors on false-positive, false-negative, and invalid fibronectin results in the prediction of spontaneous delivery within 7 days. Methods We studied symptomatic women between 24 and 34 weeks' gestational age. We performed uni- and multivariable logistic regression to estimate the effect of external factors (vaginal soap, digital examination, transvaginal sonography, sexual intercourse, vaginal bleeding) on the risk of false-positive, false-negative, and invalid results, using spontaneous delivery within 7 days as the outcome. Results Out of 708 women, 237 (33%) had a false-positive result; none of the factors showed a significant association. Vaginal bleeding increased the proportion of positive fetal fibronectin (fFN) results, but was significantly associated with a lower risk of false-positive test results (odds ratio [OR], 0.22; 95% confidence intervals [CI], 0.12–0.39). Ten women (1%) had a false-negative result. None of the investigated factors was significantly associated with a significantly higher risk of false-negative results. Twenty-one tests (3%) were invalid; only vaginal bleeding showed a significant association (OR, 4.5; 95% CI, 1.7–12). Conclusion The effect of external factors on the performance of qualitative fFN testing is limited, with vaginal bleeding as the only factor that reduces its validity.

Objective: To assess the effect of maintenance tocolysis in women who are at high or low risk for preterm delivery according to fetal fibronectin (fFN) status and cervical length (CL). Study Design: We compared the risk of preterm delivery in fFN pos and fFN neg women and in women with a CL <15 mm and ≥15 mm, by using the Cox regression. Differences between the effectiveness of maintenance tocolysis in high- and low-risk women were assessed by using an interaction term. Results: 122 fFN tests were taken, of which 50 were fFN pos. CL was measured in 236 women, of whom 52 women had a CL <15 mm. The median gestational age at delivery was lower in fFN pos women; fFN pos women had a higher hazard for preterm delivery at any point of time (HR 4.7; 95% CI 2.9 to 7.6). Comparable results were seen for CL. Neither fFN status nor CL did alter the effect of maintenance tocolysis, which was ineffective in the total randomized group, on the risk of preterm delivery (p for interaction = 0.87 for fFN and 0.18 for CL). Conclusion: Maintenance tocolytic therapy with nifedipine is ineffective and not dependent on fFN or CL status.Carolien Roos, Jolande Y. Vis, Hubertina C.J. Scheepers, Kitty W.M. Bloemenkamp, Hans J.J. Duvekot, Jim van Eyck, Christianne de Groot, Joke H. Kok, Brent C. Opmeer, Martijn A. Oudijk, Dimitri N.M. Papatsonis, Martina M. Porath, Krystyna Sollie, Marc E.A. Spaanderman, Fred K. Lotgering, Joris A.M. van der Post, and Ben Willem J. Mo

Purpose Transvaginal cervical length measurement in women with symptoms of preterm labor has been used to decide if treatment is necessary. Cervical length measurement may also have additional effects on patients, such as providing reassurance, although the evidence to support this is unclear. We explored and summarized to what extent additional effects of cervical length measurement in women with threatened preterm labor have been reported in the clinical literature and what the magnitude of these effects was. Methods We performed a systematic review of the literature to identify articles reporting on cervical length measurements in women with symptoms of preterm labor. We assessed whether these articles reported patient outcomes other than preterm delivery. Results The electronic and hand search resulted in 764 articles, of which 172 met initial criteria for further eligibility assessment. We found 12 articles that reported additional effects of cervical length measurement in symptomatic women, such as the reassurance or the sensory consequences related to the transvaginal procedure. None of the articles quantified such additional effects. Conclusions There appears to be a gap between the presumed effects of cervical length measurement on patient outcomes, such as patients’ reassurance, and the actual assessment of these effects during test evaluations. We suggest that future evaluations of prognostic preterm labor tests include a comprehensive assessment of patient outcomes.

Randomized trials on the clinical utility of fetal fibronectin in women with symptoms of preterm labor have thus far failed to demonstrate benefits. We systematically reviewed the methodology of these trials to assess if these negative results may be related to their study designs. We searched the literature for randomized trials that evaluated fibronectin testing in women with symptoms of preterm labor. Study results were evaluated and five methodological criteria were assessed: (1) randomization of discordant test results, (2) use of a fixed management protocol, (3) description of interventions in relation to the test result, (4) evaluation of a learning curve, and (5) sample size calculation in agreement with the prevalence of the test results. We detected four randomized trials that met inclusion criteria. All trials allocated women to a strategy with or without availability of fibronectin results without using a discordancy design or a fixed management protocol. One study reported the given treatment in relation to the test results. Learning curves were evaluated in one study. Two studies used transport sample size calculations. The negative results of randomized trials on fetal fibronectin may be due to particular choices in their study design.

At present, women with threatened preterm labor before 32 weeks of gestation are, after transfer to a perinatal center, treated with tocolytics and corticosteroids. Many of these women are treated unnecessarily. Fibronectin is an accurate predictor for the occurrence of preterm birth among women with threatened preterm labor. We will assess whether triage of these women with fibronectin testing, cervical length or their combination is cost-effective.