Introduction
The presence of congenital uterine anomaly is associated with increased risk of miscarriage and spontaneous preterm birth (sPTB). The mechanism is unclear, but may be related to stretch or cervical insufficiency. Fetal fibronectin (fFN) and cervical length (CL) are the current gold standard for prediction of sPTB in both symptomatic and asymptomatic women at high risk. However, it has not been established whether these tests remain reliable in women with congenital uterine anomaly.
Methods
Prospectively collected data from women attending a high-risk Preterm Surveillance Clinic between 2002 and 2015 with congenital uterine anomaly (unicornuate, bicornuate, uterus didelphus, septate or arcuate uterus) and singleton pregnancy were analysed. fFN and CL measurements from the first visit between 22+0 and 24+6 were included. fFN >50ng/mL and CL <25mm were considered ‘positive’. Predictive statistics were calculated and compared for delivery before 34 and 37 weeks’ gestation.
Results
In this cohort, 24% (15/63) had a preterm delivery before 37 weeks’, and 10% (6/63) delivered before 34 weeks’.
For delivery before 37 and 34 weeks gestation, the positive likelihood ratios for CL were 12.8 (95% CI 1.55 to 105.92) and 14.25 (95% CI 2.94 to 69.12) respectively, compared to 2.57 (95% CI 0.65 to 10.15) and 4.56 (95% CI 1.17 to 17.79) for fFN.
Negative likelihood ratios for both predictive tests were similar.
Conclusion
Women with congenital uterine anomalies are at high risk of sPTB. Within this group, CL appears to be a particularly reliable predictor, better than fFN. This is contrary to other populations. It is therefore important that clinicians are aware of this difference when planning management. Future research is needed to investigate the role of fFN in this population, and whether standard interventions such as ultrasound-indicated cerclage are equally valid in this group.