Lockwood C J, Moscarelli R D, Wein R, Lynch L, Lapinski R H, Ghidini A
Department of Obstetrics, Gynecology, and Reproductive Sciences, Mount Sinai School of Medicine, New York, NY 10029.
Am J Obstet Gynecol. 1994 Jul;171(1):1-4. doi: 10.1016/s0002-9378(94)70068-0.
This study sought to determine whether low concentrations of fetal fibronectin in the cervical and vaginal secretions of patients at 39 weeks' gestation predicted pregnancies progressing beyond 41 weeks' gestation.
A retrospective cohort study was undertaken using cervical and vaginal samples collected from 75 consenting patients during the thirty-ninth week of gestation. Levels of fetal fibronectin were measured by immunoassay. Demographic, obstetric, neonatal, and laboratory data were analyzed by Fisher's exact test, Student t test or Wilcoxon's rank-sum test, multiple logistic regression, and receiver-operating characteristic curve analysis.
There was a 35.5-fold increase in vaginal fetal fibronectin concentrations among patients delivered at < 41 weeks compared with those delivered at > or = 41 weeks. The receiver-operating characteristic curve analysis indicated that the optimal fetal fibronectin predictor of prolonged pregnancies was a vaginal fetal fibronectin value < 60 ng/ml present between 39 weeks 0 days and 39 weeks 6 days' gestation (sensitivity 95.7%, 95% confidence interval 87.3% to 100.0%; specificity 44.2%, 95% confidence interval 30.7% to 57.7%; positive and negative predictive values 43.1% [95% confidence interval 29.5% to 56.7%] and 95.8% [95% confidence interval 87.8% to 100.0%], respectively). The relative risk for a prolonged pregnancy resulting from a vaginal fetal fibronectin value < 60 ng/ml was 10.4 (1.5 to 72.4). Among patients with a vaginal fetal fibronectin value > or = 60 ng/ml, 80.8% were delivered within 1 week and 92.3% within 10 days of sampling. In contrast, among patients with vaginal fetal fibronectin value < 60 ng/ml 63.3% remained undelivered after 1 week. After parity and cervical dilation were controlled for, multiple logistic regression demonstrated that a vaginal fetal fibronectin value < 60 ng/ml was a significant independent predictor of pregnancies delivered at > or = 41 weeks (adjusted odds ratio 12.8 [95% confidence interval 1.5 to 107.2]).
A vaginal fetal fibronectin value > or = 60 ng/ml at 39 weeks' gestation is predictive of delivery within 10 days, whereas values < 60 ng/ml identify 95% of pregnancies progressing past 41 weeks' gestation. This data may allow for the prediction of postdates pregnancies, thus facilitating appropriate obstetric interventions.
