Abstract Placental dysfunction originates during placental development, specifically the events of placentation. Vascularization is a key component of placentation due to its role in fetal-maternal exchange. Cytokines are regulators of placental development; signaling of chemokine ligand 12 (CXCL12) and its receptor (CXCR4) drives placental vascularization. Utilizing an in vivo sheep model, we demonstrated that suppressing CXCL12-CXCR4 signaling at the fetal-maternal interface reduces placental vascularization. We hypothesized these negative impacts early in gestation would result in compromised placental development and vascularization at mid to late gestation. On day 12 post-breeding, osmotic pumps were surgically installed in 37 ewes and delivered either CXCR4 inhibitor (AMD3100) at 1x dose (n = 8),1.5X dose (n = 8), or 3X dose (n = 8) or saline (n = 13) into the uterine lumen ipsilateral to the corpus luteum for 14 days. On day 90 and day 135 placental tissues were collected and maternal (caruncle) and fetal (cotyledon) placenta components were separated and analyzed. Gene expression of angiogenic factors were analyzed using Real-time qPCR. Gene expression was significantly altered by AMD3100 treatment for the vascular endothelial growth factor receptors (FLT-1 and KDR) primarily in day 90 placenta contralateral to the corpus luteum. Significant decreases in KDR were seen in 3x compared to control (P < 0.03), 3x compared to 1.5x (P < 0.008), and 3x contralateral compared to ipsilateral (P < 0.01); however, FLT-1 significantly increased (P < 0.02) from control to 1.5x. Day 90 caruncle tissue had significant increases in FLT-1 from control to 3x (0.02), 1.5x to 3x (P < 0.03); however, 1.5x treatment FLT-1 significantly decreased (P < 0.02) ipsilateral to contralateral. Fibroblast growth factor 2 increased in both contralateral 3x compared to control cotyledon (P < 0.03) and caruncle (P < 0.03). Our data underscore the importance of CXCL12-CXCR4 signaling during placentation and provide strong evidence that altering CXCR4-mediated signaling during early placentation induces enduring effects altering vascular development later in gestation. A greater understanding of CXCL12/CXCR4 functions may reveal methods to improve reproductive success and fetal health.