CXCL12 and gonorrhea: The chemokine CXCL12 and the receptor CXCR4/CXCR7 are highly expressed in trophoblast cells due to PAS, and the expression intensity of CXCL12, CXCR4 and CXCR7 proteins is closely related to the invasion depth of trophoblast cells, which indicates that CXCL12‐CXCR4/CXCR7 may play an important role in the development of PAS.