Down-regulation of miR-29b in the placental tissues from patients with GDM detected by qRT-PCR. The overall expression trend of miR-29b in all placental tissues of GDM group was lower than that in control group. (A) The GDM patients were grouped into six groups according to OGTT values in blood, including 1st h, 2nd h, 0 and 1st h, 0 and 2nd h, 1st and 2nd h, 0 and 1st and 2nd h (B). The GDM placental tissues were also grouped into four groups according to age, including ≤25 Y, 26–30 Y, 31–35 Y, and ≥36 Y. There was a trend toward a decrease in the level of expression miR-29b in normal placenta with age (C). MiR-29b expression level was significantly down-regulated in the groups of ≤25 Y, 26–30 Y, and 31–35 Y as compared with matched control (D). Random 10 pair samples (n = 10) in each age group (OGTT 1st h, 2nd h, 0 and 1st h, 0 and 2nd h, 1st and 2nd h, 0 and 1st and 2nd h); (B) and random 15 pair samples (n = 15) in each age group (≤ 25 Y, 26–30 Y, 31–35 Y, ≥36 Y); (C) were selected for qRT-PCR. Each sample in each experiment was detected in triplicate. U6 serves as an internal reference to normalize the experimental error (E). Placentas from 204 GDM patients and 202 normal pregnant women were separately arranged into two tissue microarrays according to the match between the case group and the control group, and detected by in situ hybridization. The stain was developed with BCIP/NBT. Black arrows indicate hybridization signals and the positive signals of miR-29b are blue. *P < 0.05.