Fetal fibronectin status and cervical length in women with threatened preterm labor and the effectiveness of maintenance tocolysis

Abstract

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.

• Cervical length
• fetal fibronectin
• maintenance tocolysis

Acknowledgements

We thank research nurses, midwives and secretaries of our consortium; and the residents, nurses and gynecologists of the participating centers, for their help with participant recruitment and data collection.

Declaration of interest

All authors will complete the unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: they had financial support for the submitted work from ZonMw, the Netherlands Organisation for Health Research and Development healthcare efficiency programme (grant number 80-82310-98-08210); no financial relationships with any organizations that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work. The funder had no role in study design; collection, analysis and interpretation of data; writing the report; or the decision to submit for publication.

All authors participated in recruitment of participants and collected data. CR and JYV analyzed and interpreted the data. FKL, BWJM and BCO provided background knowledge to the data analysis and interpretation. CR drafted the manuscript. All authors critically reviewed the report. All authors have seen and approved the final version.

This trial was approved by the Academic Medical Center institutional review board (MEC 07/286). Written informed consent was obtained from all participants before enrolment.

Notes

* Trial register number: NTR 1336. Presented in part at the 31st Annual Meeting of the Society for Maternal-Fetal Medicine: poster presentation February 2010, San Francisco, California (abstract #497).