Laboratory and Clinical Values of the Neutrophil-to-Lymphocyte Ratio in Women With Hyperemesis Gravidarum: A Systematic Review and Meta-Analysis.

Introduction: Hyperemesis gravidarum (HG), which is characterized by severe nausea and vomiting, can lead to maternal complications and adverse fetal outcomes. The neutrophil-to-lymphocyte ratio (NLR) is a potentially simple and cost-effective marker for detecting this condition. The aim of this study was to consolidate the current evidence regarding the utility of NLR in diagnosing and assessing the severity of HG. Methods: A systematic search of Scopus, PubMed, Web of Science, Embase, and Google Scholar was conducted before March 2024. The selected articles were reviewed. Analytical cross-sectional studies reporting NLR values in patients with HG were included. Two independent authors reviewed the articles and assessed them for bias. A meta-analysis with random effects was conducted to compare NLR values between HG and healthy patients and to evaluate its association with the severity of symptoms assessed through the modified Pregnancy-Unique Quantification of Emesis, such as ketonuria and C-reactive protein levels. The GRADE system determined the certainty of the evidence. Results: Fifteen studies were included, predominantly case-control. Pooled analysis revealed a significant elevation in NLR among patients with HG compared with healthy pregnant women (MD: 1.76; 95% CI: 1.15-2.37; Discussion: With low certainty, the mean NLR was higher in patients with HG than in healthy pregnant women, with moderate certainty regarding severity. These findings suggest the potential utility of NLR; however, further research on neonatal and long-term outcomes is needed. Precis: These results indicate that NLR could be useful, but additional studies are necessary to understand its impact on neonatal and long-term outcomes.