Impact of Complete Blood Count (CBC) Parameters in Preterm Birth Prediction in Cases with Threatened Preterm Labour (TPL)

Background: Preterm birth is one of the main causes of neonatal morbidity and mortality in pregnancies worldwide. This investigation is undertaken to determine the usefulness of neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR), which are complete blood count (CBC) parameters, in predicting preterm birth among women with threatened preterm labour (TPL). Methods: A retrospective observational study was conducted between 2019 and 2023, and medical charts of 250 pregnant patients internalized for TPL were investigated. A hundred and forty of them gave birth prematurely, and remaining 110 women who responded to bed rest and medical treatment constituted the control group. NLR, PLR and other inflammatory markers such as systemic immune-inflammation index (SII = neutrophil × platelet/lymphocyte count) were recorded, and their probable correlations with preterm delivery were evaluated. Logistic regression and area under curve (AUC) analysis were used to assess the predictive value of these markers. Results: There were no significant differences between those who delivered at term and patients with preterm labour who delivered <37 weeks according to demographic data and gestational history. However, there were notable discrepancies when considering certain clinical and laboratory findings, such as cervical length (CL), SII, and NLR. CL had a strong relationship with the risk of preterm delivery (odds ratio (OR) = 0.95, 95% confidence interval (CI) = 0.92–0.98, p = 0.001). SII and NLR values were seen to be higher in patients with preterm labour compared with control group, indicating a rise in inflammatory activity (1489.4 ± 1113.3 vs. 1043.9 ± 587.1, respectively, p = 0.001 for SII; and 5.6 ± 3.4 vs. 4.8 ± 3.0, respectively, p = 0.02 for NLR). However, NLR had a low predictive power with an AUC of 0.581. Conclusions: SII seems to have an important predictive value for preterm delivery, similar to CL measurements already used in the clinic. Even patients with preterm delivery had higher NLR, clinical interpretation of AUC value reduces its predictive power. Therefore, further research is needed to refine our results and to advance its use in clinical practice.