Fig 2: Representative diaminobenzidine (brown) and hematoxylin (blue) staining (A–D, 400X magnification), and staining quantification (E–H) for placental NGAL. (A) BPD, TE group (n = 5), with strong (3 to 4+) NGAL-positive staining in a chorionic plate and subchorionic space. (B) BPD, no TE group (n = 9), with mild (1–2+) NGAL-positive staining only in subchorionic space. (C) No BPD, TE group (n = 10), with strong (3–4+) NGAL-positive staining in the chorionic plate and subchorionic space. (D) No BPD, no TE group (n = 12), with rare (0–1+) NGAL-positive staining only in subchorionic space. (E,F) Quantification of chorionic plate staining stratified by maternal smoking status and subgroup analysis. (G,H) Quantification of subchorionic space staining stratified by maternal smoking status and subgroup analysis. NGAL—neutrophil gelatinase-associated lipocalin, BPD—bronchopulmonary dysplasia, and TE—tobacco exposure.