Identification of preterm birth in women with threatened preterm labour between 34 and 37 weeks of gestation

The aim of this study was to assess whether serum markers would be useful as a new predictor of preterm birth in patients with spontaneous, late preterm labour. Patients diagnosed with late preterm labour were divided into preterm delivery (229 patients) and term delivery (178 patients) groups. The two groups were compared in terms of clinical characteristics and levels of serum markers (leukocyte subtypes, platelet, C-reactive protein [CRP], neutrophil to lymphocyte ratio [NLR] and platelet to lymphocyte ratio [PLR]), which were obtained at admission. The levels of leukocyte (p < .001), neutrophil (p < .001), CRP (p = .001), NLR (p < .001) and PLR (p = .003) were significantly higher, whereas lymphocytes (p = .012) were significantly lower in the preterm delivery group, compared to the term delivery group. On multivariate regression analysis, NLR positive was the most powerful predictive variable (OR = 1.41; 95%CI: 1.32-1.51; p = .005). NLR had the highest area under curve (0.711; 95%CI 0.662-0.760) in predicting preterm birth and a NLR >6.2 had the highest sensitivity (65.1%) and specificity (62.5%). High NLR at admission is an independent predictor of preterm birth in patients with spontaneous, late preterm labour. Impact statement What is already known on this subject: Preterm birth accounts for 5-12% of all births, and is a major factor associated with perinatal morbidity and mortality worldwide. However, more than 70% of preterm births occur at late preterm between 34^0/7 and 36^6/7 weeks of gestation. The central role of systemic and subclinical infections in preterm labour is well documented. Intrauterine infection leading to delivery can be measured by using a variety of laboratory parameters. What do the results of this study add: Neutrophil to lymphocyte ratio is an inexpensive, easily interpretable and promising haematologic parameter that is widely available. This study explored the association of high neutrophil to lymphocyte ratio with the risk of preterm birth in women with preterm labour between 34 and 37 weeks of gestation. What are the implications of these findings for clinical practice and/or further research: Neutrophil to lymphocyte ratio could be used in combination with existing markers to improve detection rates of preterm birth. Concomitant use of markers could be more powerful than measuring any of the individual markers alone.