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. Author manuscript; available in PMC: 2015 Aug 15.
Published in final edited form as: Science. 2014 Aug 14;345(6198):760–765. doi: 10.1126/science.1251816

Figure 4.

Figure 4

A subset of patients with preterm labor has placental vascular lesions, including failure of physiologic transformation of the uterine spiral arteries. (A) Schematic drawing of the maternal-fetal interface in normal pregnancy. A physiologically transformed uterine spiral artery with a wide lumen delivers blood to the intervillous space of the placenta to supply blood to villi. (B) A spiral artery with an expanded ostium that normally enables adequate perfusion of the intervillous space. (C) Ostium of a narrow spiral artery with failure of physiologic transformation in a patient with spontaneous preterm labor. (D) PAS staining of a histological section of the maternal-fetal interface in normal pregnancy shows a spiral artery transformed by cytokeratin 7-positive cytotrophoblasts (brown) that line the lumen (200x). (E) Failure of physiologic transformation of a spiral artery in a patient with preterm labor. The lumen is narrow and cytotrophoblasts have not invaded the muscular wall (200×).