Association between Serum HLA-G Levels in The First Trimester of Pregnancy and The Onset of Preeclampsia: A Systematic Review and Meta-analysis Study

Human leukocyte antigen G (HLA-G) levels are among the biomarkers suggested for pre-eclampsia (PE). This study is aimed at determining the possible relationship between low soluble HLA-G (sHLA-G) levels in maternal blood at the beginning of pregnancy and subsequent PE. We searched the international scientific databases of Web of Science, Embase, PubMed, Cochrane, and Scopus. We extracted the studies investigating the relationship between the serum levels of HLA-G in the first trimester of pregnancy and the onset of PE using the appropriate keywords. The collected data were analyzed using the random-effects meta-analysis model and STATA (version 14). A total of 5 studies met the eligibility criteria, and the total sample size was 668 subjects. The mean and SD age of case subjects was 31.41 ± 4.16 years, while it was 30.56 ± 3.5 for control subjects. According to the findings, there was an inverse relationship between HLA-G serum level in the first trimester of pregnancy and the subsequent onset of PE, standard mean difference (SMD)=-1.51 [95% confidence interval (CI): -2.26, -0.75, I2=90.8%, P=0.000]. Based on these results, low sHLA-G level in early pregnancy has a positive correlation with subsequent PE, and the significant role of sHLA-G in the early stages of placentation can be proven.