Neutrophil and Neutrophil-to-Lymphocyte Ratio as Clinically Predictive Risk Markers for Recurrent Pregnancy Loss

We aimed at exploring the value of neutrophil and neutrophil-to-lymphocyte ratio (NLR) as predictive risk markers for recurrent pregnancy loss (RPL) by conducting a retrospective case-control study and a systematic review and meta-analysis. This retrospective case-control study was conducted in an academic hospital from January 2012 to June 2018 and 133 cases of women with RPL and 140 control women. In parallel, we conducted a systematic review and meta-analysis on the value of NLR and neutrophil in RPL risk assessment. Neutrophil and NLR were higher in the women with RPL than those in the controls (median [interquartile range]: 4.32 [3.31-6.18] vs. 3.76 [2.78-4.81], p = 0.001; 2.17 [1.47-3.16] vs. 1.74 [1.40-2.34], p = 0.001). After the cut-off value of the neutrophil and NLR was determined to be 6.3 x 10(9)/L and 3.16, the prevalence of RPL became significantly increased in the high-neutrophil and the high-NLR group compared to the low-neutrophil and the low-NLR group (76.3% vs. 44.2%, p < 0.001; 66.6% vs. 44.5%, p < 0.001). Univariate logistic regression analysis indicated that high-neutrophil and high-NLR were risk factors for RPL, with ORs of 4.06 (95% CI: 1.84-8.95) and 2.49 (95% CI: 1.31-4.71), respectively. Multivariate logistic regression analysis indicated that high-neutrophil was a risk factor for RPL, with OR of 4.91 (95% CI: 1.66-14.50). Meta-analysis of 5 case-control studies (including the present study) indicated that increased neutrophil and NLR may be risk factors for RPL, with SMDs of 0.63 (95% CI: 0.45-0.80) and 0.61 (95% CI: 0.39-0.83). Based on current findings and the meta-analysis, this study indicated that neutrophil and NLR might be valuable for predicting RPL; more studies with large sample are needed to verify this conclusion. The mechanism of the association between neutrophil and RPL needs to be explored in further studies.

Automated summary

This study aimed to investigate the role of neutrophil and neutrophil-to-lymphocyte ratio (NLR) as predictive risk markers for recurrent pregnancy loss (RPL) through a retrospective case-control study and a meta-analysis. The findings suggest that high neutrophil and NLR levels could be potential risk factors for RPL, and further large-scale studies are needed to confirm these associations.