Endometrial vascular endothelial growth factor levels will be measured using Flk-1 / Kinase Domain Receptor / Vascular endothelial growth factor receptor-2, Ab-1 (Rabbit PAb), Vascular Endothelial Growth Factor (VEGF) Ab-7 (VG1), Cluster of Differentiation 34 (Endothelial Cell Marker) Ab-1 (QBEnd/10), Vascular endothelial growth factor receptor-1 (N-term) (FLT1) antibody kits. All assays will be performed according to the manufacturer's instructions.