(A) Flow cytometry gating strategy to identify and quantify uNK cells in control and obese women. Live decidual leukocytes were selected by excluding nonviable cells and CD3⁺ lymphocytes. uNK cell proportions within the CD45⁺ fraction were quantified by their surface expression of CD56 and CD16 and are presented as proportion of cells. SSC, side scatter. (B) Representative flow cytometry plots of uNK cell proportions in control (n = 16) and obese (n = 16) women. Median values of CD56^bright cells are shown within plots. IQR, interquartile range. (C) Scatter plots depicting CD56^bright cell proportions in control and obese women; horizontal line indicates group median. (D) Representative immunofluorescence images of first trimester decidual tissue (11–13 weeks of gestation) from control (n = 10) and obese (n = 10) women immunostained with antibodies directed against CD56 (green), smooth muscle actin (SMA; red), and CD31 (red); DAPI-stained nuclei are labeled blue. Scale bars: 50 μm. The perforated white box indicates enlarged image. Quantification of (E) absolute uNK cell numbers, (F) arterial smooth muscle thickness, (G) arterial vessel:lumen ratios and (H) numbers of small (< 100-μm diameter) and large (≥ 100-μm diameter) arteries per field of view from decidual specimens of control (C) and obese (O) women. Representative immunofluorescence images (I) and quantification of proportions of apoptosing uNK cells (J) in decidual tissue from control (n = 10) and obese (n = 10) women. Sections were immunostained with antibodies directed against CD56 (red) and cleaved caspase-3 (cl-CASP3; green); DAPI-stained nuclei are labeled blue. White arrowheads highlight apoptosing uNK cells. Scale bars: 50 μm. Statistical analyses were performed using a nonparametric 2-tailed Mann-Whitney t test.