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Published on: June 2, 2019
Association between the neutrophil-to-lymphocyte ratio and preeclampsia: a systematic review and meta-analysis of
Xinqian Li1, Duqin Chen2, Ping Che3
1Bioscience, School of Health Industry, Chongqing Vocational College of Applied Technology, Chongqing, China.
Background:
Preeclampsia is a pregnancy-specific hypertensive disorder associated with substantial maternal and perinatal morbidity. The neutrophil-to-lymphocyte ratio (NLR) has emerged as a potential inflammatory biomarker, but existing evidence remains inconsistent.
Methods:
PubMed, Embase, and Web of Science Core Collection were searched from database inception to 9 March 2026. Observational studies comparing NLR between women with preeclampsia and normotensive pregnant controls were included. Study quality was assessed using the Newcastle-Ottawa Scale. Random-effects meta-analysis was used to calculate pooled standardized mean differences (SMDs), with Hartung-Knapp adjustment applied as a sensitivity analysis. Publication bias was assessed using funnel plot inspection, Egger's test, and Begg's test.
Results:
Fourteen studies were included in the qualitative synthesis and eleven in the quantitative synthesis. The pooled analysis demonstrated significantly higher NLR levels in women with preeclampsia (SMD = 0.76, 95% CI 0.54-0.98; I 2 = 84.8%). Subgroup analysis showed significant associations both in studies measuring NLR in the first trimester or early pregnancy (SMD = 0.81, 95% CI 0.48-1.14; I 2 = 88.7%) and in studies measuring NLR at other time points (SMD = 0.73, 95% CI 0.40-1.06; I 2 = 83.4%). The test for subgroup differences was not statistically significant (p = 0.743), although this comparison was limited by the small number of studies in each subgroup. Formal tests did not detect statistically significant publication bias, but their power was limited by the small number of studies.
Conclusion:
Maternal NLR was significantly higher in women with preeclampsia than in normotensive pregnant controls. However, because the included studies were observational and showed substantial heterogeneity, and because diagnostic accuracy metrics and clinically actionable thresholds were not synthesized, NLR should not be interpreted as a stand-alone diagnostic or predictive marker. Further prospective studies with standardized sampling windows, prespecified cut-off values, and adjustment for key confounders are needed.
Systematic Review Registration:
Identifier PROSPERO CRD420261333930.