This study aimed to investigate the regulation of amniotic fibroblast (AFC) function by vitamin K-dependent protein Z (PROZ) during preterm birth (PTB) and its potential role in adverse pregnancy outcomes. Proteomic samples were collected from amniotic fluid in the second trimester, and AFC were isolated from the amniotic membrane and cultured in vitro. The expression of extracellular and intracellular PROZ in AFC was modulated, and their biological properties and functions were evaluated. Clinical analysis revealed a significant upregulation of PROZ expression in amniotic fluid from preterm pregnant women. In vitro experiments demonstrated that PROZ stimulated AFC migration, enhanced their proliferative capacity, and reduced collagen secretion. Overexpression of PROZ further enhanced cell migration and proliferation, while knockdown of PROZ had the opposite effect. PROZ plays a crucial role in promoting the proliferation and migration of amniotic membrane fibroblasts. Increased PROZ expression in amniotic fluid is associated with the occurrence of PTB. These findings shed light on the potential involvement of PROZ in adverse pregnancy outcomes and provide a basis for further research on its regulatory mechanisms during PTB.© 2024. The Author(s).