Combined fetal fibronectin and cervical length and spontaneous preterm birth in asymptomatic triplet pregnancies

Abstract

Objective: To estimate the association between fetal fibronectin (fFN), cervical length (CL), and spontaneous preterm birth (SPTB) in asymptomatic women with triplet pregnancies. Study design: A cohort of 39 consecutive women with triplet pregnancies managed in one Maternal-Fetal medicine practice from 2005–2011 was analyzed. Combined fFN and CL testing was performed every 2 weeks from 22–32 weeks. A short CL was defined as ≤20 mm. Results: A positive fFN was significantly associated with SPTB <28 weeks, <30 weeks, <32 weeks, and <34 weeks. A short CL was significantly associated with SPTB <32 weeks. On combined testing, having both tests positive was associated with the highest likelihood of SPTB at all gestational ages. As a screening test for SPTB <32 weeks, having both a positive fFN and a short CL had a sensitivity of 62.5%, specificity of 90%, positive predictive value of 62.5%, negative predictive value of 90%, positive likelihood ration of 2.98 and negative likelihood ratio of 0.88. Combined fFN and CL outperformed fFN alone, CL alone, or either test being positive alone. Conclusions: In asymptomatic women with triplet pregnancies, fFN and CL are each significantly associated with SPTB. For the prediction of SPTB, combined fFN and CL testing outperforms either test alone.

Keywords::

• Cervical length
• fetal fibronectin
• preterm birth
• triplets

Declaration of Interest: Dr. Ashley Roman is a consultant for Hologic Inc, the company that makes and markets the fetal fibronectin test. Otherwise, the authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.