AIM:To investigate the clinical significance of microRNA-26a-5p (miR-26a-5p)-regulated mye-loid cell leukemia-1 (MCL-1) expression in the development of maternal preeclampsia.METHODS:Plasma and placen-tal tissues were collected from 21 cases of normal pregnancy, 13 cases of maternal gestational hypertension, 15 cases of mild preeclampsia and 26 cases of severe preeclampsia.The levels of plasma and placental miR-26a-5p and placental MCL-1 mRNA were detected by real-time PCR.Western blotting analysis was used to determine the protein expression of placen-tal MCL-1.The clinical significance of the above parameters was also analyzed.RESULTS:miR-26a-5p expression gradu-ally increased(P<0.01) in the 4 groups of maternal plasma and placentas with the disease development, and the mRNA expression of MCL-1 was significantly reduced in the placentas (P<0.01), both showing a significant negative correlation (P<0.01).Meanwhile, the expression of miR-26a-5p and MCL-1 protein in the placental tissues was negatively correla-ted (P<0.01).The miR-26a-5p up-regulation in maternal plasma and placental tissues was negatively correlated with ges-tational age, maternal plasma albumin levels and fetal weight, while it was positively correlated with maternal blood pres-sure and urinary protein level (P<0.01), which was in contrary to the down-regulation of placental MCL-1.CONCLU-SION:Up-regulation of miR-26a-5p is involved in the occurrence and development of preeclampsia by down-regulation of MCL-1.