Prenatal caffeine exposure disrupts the fetal-placental-maternal bile acid circulation and its associated placental transport mechanisms.

Prenatal caffeine exposure (PCE) is linked to fetal growth restriction (FGR) and has been associated with bile-acid-related pregnancy complications. Because the fetal-placental-maternal bile-acid (BA) circulation is essential for pregnancy homeostasis and fetal development, we asked whether PCE disrupts BA balance across these compartments and sought the underlying placental mechanism. We established a rat model of PCE and analyzed placental samples from pregnancies complicated by FGR. Targeted BA metabolomics, transporter expression assays, cAMP/PKA signaling measurements, and trophoblast functional assays were performed to delineate the mechanism. PCE increased maternal serum total bile acids but reduced BAs in male fetuses; female fetuses were unchanged. Male placentas exhibited increased OATP2B1 and BCRP and decreased MRP4, consistent with sex-biased remodeling of placental BA transport. In BeWo cells, caffeine altered taurocholic-acid transport, changed transporter expression, and suppressed A2AR-dependent cAMP/PKA/SP1 signaling; pharmacologic activation of A2AR or cAMP partially reversed these effects. In human FGR placentas, OATP2B1 was elevated and SP1 signaling was attenuated. PCE reprograms placental BA transport by inhibiting the A2AR-cAMP/PKA-SP1 axis, potentially enhancing fetal-to-maternal BA efflux, increasing a cholestasis-like maternal BA load, and contributing to male fetal hypo-bileacidemic. Altered placental BA transport may therefore link prenatal caffeine exposure to sex-specific fetal vulnerability.