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Background: Premature birth (PTB) remains a major global health concern due to its association with neonatal morbidity and mortality. The unfolded protein response (UPR) within the endoplasmic reticulum (ER) is tightly regulated by Inositol‐requiring enzyme type 1 (IRE‐1), a pivotal cellular modulator. This study seeks to elucidate the role of the ER stress (ERS)‐related IRE‐1 pathway in PTB. Methods: Human placental trophoblast cells HTR8/Svneo were exposed to the ER‐stress inducer tunicamycin (TM). The expression of IRE‐1 and ERS‐associated proteins ATF6, GRP78, and XBP‐1 was assessed in placental tissues and TM‐treated cells. Cellular viability, migration, invasion, and apoptosis were evaluated through a series of experimental assays. Additionally, various methods were employed to assess and verify the activation of autophagy, using the autophagy marker, microtubule‐associated protein 1A/1B‐light chain 3 (LC3). Additionally, TUDCA (an ERS inhibitor) was used to assess its potential to counteract the TM‐induced cell effects. Results: Elevated levels of ATF6, GRP78, and XBP‐1 were observed in PTB tissues and cells. TM treatment substantially reduced cell viability, migration, and invasion while promoting apoptosis. Treatment with TUDCA (an ERS inhibitor) counteracted the effects of TM on the cells. Furthermore, we identified an overexpression of IRE‐1 in PTB tissues and cells and its knockdown enhanced cell viability, migration, and invasion while suppressed apoptosis and autophagy under TM stimulation. Notably, IRE‐1 was found to modulate the activity of the IRE‐1/XBP1/CHOP signaling pathway in TM‐treated cells. Conclusion: The upregulation of IRE‐1 in PTB placental tissues is implicated in the pathogenesis of PTB. Importantly, inhibiting the ERS‐associated IRE‐1/XBP1/CHOP pathway may be a good strategy in mitigating PTB. [ABSTRACT FROM AUTHOR]