Background An improved understanding of inflammatory events leading to cervical shortening in women at risk of spontaneous preterm labour (SPTL) is necessary. We undertook a longitudinal observational study to determine the relationship between cytokine and fetal fibronectin (fFN) concentrations in women at risk of SPTL.

Methods Women (n=112) with at least one previous preterm delivery were recruited (14–24 weeks' gestation) from two prematurity clinics and assessed (transvaginal cervical scans and cervico-vaginal fluid (CVF) swabs) every 2 weeks until 28 weeks. If cervical length shortened (<25 mm), women were randomised to cervical cerclage or progesterone and samples taken weekly. Concentrations of 11 cytokines were measured in CVF samples (n=477 from 78 women) using multiplex immunoassay. Concentrations of fFN were measured using ELISA (n=735 from 112 women). Data were analysed using STATA; results expressed as ratios (95% CI).

Results There was no difference in CVF fFN concentrations in women destined to develop a short cervix (n=36) compared to high-risk women without a short cervix (n=76). Women with a positive fFN exhibited higher CVF concentrations of interleukin-6 (IL) (1.53 (1.21–1.94), p<0.001) IL-7 (1.19 (1.02–1.39), p=0.03), Granulocyte colony-stimulating factor (G-CSF) (1.25 (1.00–1.57), p=0.05), interferon-γ (IFN-γ) (1.28 (1.01–1.61), p=0.04), monocyte chemoattractant protein 1 (MCP-1) (1.18 (1.00–1.38), p=0.05) and Macrophage inflammatory protein 1β (MIP-1) (1.43 (1.04–1.97), p=0.03) at the same gestational age. Doubling concentrations of IL-6 and TNF α were associated with a positive fFN test 2 weeks later (1.32 (1.00–1.73), p=0.05 and 1.50 (CI 1.01 to 2.24), p=0.05, respectively).

Conclusions Elevated CVF IL-6, IL-7, G-CSF, IFN-γ, MCP-1 and MIP-1β concentrations are associated with a positive fFN test. fFN does not appear to be involved in the processes leading to cervical shortening.