Gestational Diabetes Mellitus (GDM) is a common pregnancy related disease. Diabetes mellitus affects 2.5% of pregnancies of which 65% are gestational diabetes mellitus and 35% are complicated by pre-existing diabetes mellitus. The placenta is an important organ serving as a connection between mother and growing fetus. This critical organ undergoes drastic modification in response to hyperglycemic condition. Previous studies have shown that GDM alters placental morphology, vascular patterns and histopathological features. However, a detailed comparative study of these parameters across different treatment modalities in GDM remain limited. This study aims to identify and analyze placenta changes associated with GDM across different treatment modalities.
To compare the changes in morphological, histopathological and vascular features between normal pregnancies and pregnancies complicated with GDM- classified by different treatment modalities as diet-controlled, tablet treated or insulin- treated patients.
In our study we have analyzed 70 placentas 50 normal pregnancies and 20 GDM pregnancies across different modalities. Placental samples were collected from OBG department of Adichunchanagiri Institute of Medical Sciences, soon after the delivery, analyzed for morphometric (cotyledon number, weight, thickness), and vascular (umbilical vein/artery pattern), then tissue samples were taken for histopathological examination for different quantitative and qualitative parameters. Statistical analyses included independent t-tests, one-way ANOVA, and chi-square tests. Findings are presented in tables and graphs.
Significant abnormalities were found in placental morphometry, architecture, and histopathology for GDM, most marked in insulin-treated cases. Magistral vascular patterns predominated in GDM groups. Syncytial knots, chorangiosis, and infarction emerged as qualitative discriminators.
Morphometric, vascular, and histopathological placental parameters are all significantly altered in GDM pregnancy. More severe changes were observed in the Insulin-treated patients. This suggest that the routine placental assessment can help us in stratifying the perinatal risk and modulate the treatment strategies in GDM patients.
Gestational diabetes mellitus (GDM) is very common disease during pregnancy which is globally affecting 2-10% of the pregnancies. GDM is characterized by intolerance to the Glucose which is first recognized during pregnancy [1]. In this condition the developing fetus is exposed to hypoxic stress which may lead to many adverse pregnancy outcomes such as premature delivery or pre-eclampsia. With the increased incidence of obesity there is an increased numbers of pregnancies diagnosed with GDM [2-4].
Placenta is a vital connection between mother and the fetus. The survival of the fetus completely depends on it [5]. Placenta word is derived from Latin word Plakos, which means cake [6]. The development of placenta occurs in three stages an early stage where there is continuous proliferation and differentiation of the trophoblast forming the primary villi. In the second stage villi undergoes branching and the villous core is filled with the mesoderm forming secondary villi, then the secondary villi are invaded by the embryonic blood vessels forming the tertiary villi. During the first half of pregnancy trophoblast undergoes drastic change while in the second half of pregnancy there will be an extensive angiogenesis and vascularization which leads to vascular remodeling and vascular stabilization [7,8].
GDM alters the intrauterine environment which affects the placental morphology, development and function leading to many fetomaternal complications [9]. It undergoes a significant adaptive changes in case of GDM. GDM management involves dietary modifications and drug therapy (tablets or insulin), when the Glycemic control cannot be achieved through dietary modifications alone. The effect of these treatment modalities on placenta morphology and histopathology is still poorly understood [10].
Previous research has reported many conflicting results about the placenta morphology in GDM patients like placenta weight and number of cotyledons [11-13]. While in other studies they have given variable results depending on the treatment modalities and degree of glycemic control [14,15]. The systemic reviews have highlighted and suggested the need of more detailed comparative studies on morphological and histopathological parameters among the different treatment modalities in GDM patients [10,16].
In our study we are aiming to provide a comprehensive analysis on placental morphometry and histopathology between normal placenta and placenta of GDM patients managed with different treatment modalities.
This prospective observational study was conducted in the department of Anatomy Adichunchanagiri Institute of Medical Science, B G Nagara, Mandya, Karnataka from January 2023 to December 2024. The study included 70 placentae from singleton pregnancies: 50 Normal 20 GDM patients. The GDM placenta were further divided into 3 categories depending upon their treatment modalities: diet control (n=5), oral hypoglycemic tablets (n=8), and insulin therapy (n=7). The informed consent was taken from the study participants and Institutional Ethics committee approval was obtained (IEC letter number AIMS/IEC/030/2022 dated 12/04/2022).
Inclusion criteria comprised singleton pregnancies delivered at term (37-42 weeks), confirmed GDM diagnosis according to International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria for the study group, and normal glucose tolerance for controls. Exclusion criteria included multiple pregnancies, pregestational diabetes, pregnancies complicated with hypertension, congenital anomalies, and intrauterine growth restriction not related to GDM.
Placenta was collected from the OBG department immediately after delivery, placenta was stored in normal saline for half an hour, then taken for the gross examination. Placental weight was measured using a calibrated digital scale. Placental diameter was measured in centimeter; two diameters were taken then the average of two measurements were taken for the study (Figure 1). Site of attachment of umbilical cord, pattern of distribution of umbilical vessels was observed. Cotyledon counting was performed systematically across the maternal surface. Central and peripheral thickness measurements were obtained using digital Vernier caliper at standardized locations [17,18] (Figure 2&3).
From each placenta three sections were taken i.e. central, paracentral and peripheral areas. Tissues were fixed in 10% formalin solution for 24 hours, and embedded in paraffin, blocks were made. 4-5 µm thickness sections were taken from the blocks and stained with hematoxylin and eosin for routine histological examination [19,20]. Quantitative histomorphometric analysis was performed using light microscopy with digital image analysis. Parameters measured included villous count per high-power field, villous diameter and perimeter, trophoblast thickness, number of capillaries per villus, capillary diameter, and blood vessel wall thickness. At least 10 random fields were examined per case [21,22].
Data analysis was performed using SPSS version 26.0. Descriptive statistics were calculated for all variables. Independent samples t-tests were used to compare continuous variables between normal and GDM groups. Chi-square tests analyzed categorical variables including cord insertion site and vascular patterns. One-way ANOVA compared multiple groups (normal vs. different GDM treatment modalities) with post-hoc Tukey's test for pairwise comparisons. Statistical significance was set at p<0.05 [23,24].
The study population comprised 70 participants with mean maternal age of 28.4 ± 4.2 years in the normal group and 29.8 ± 3.9 years in the GDM group (p=0.154). Mean gestational age at delivery was significantly lower in GDM cases (37.8 ± 1.4 weeks) compared to normal pregnancies (39.2 ± 1.1 weeks) (p<0.001). ANOVA analysis across different treatment modalities within the GDM group revealed significant differences in gestational age at delivery (F=3.794, p=0.031). Diet-controlled GDM cases had the earliest delivery (36.4 ± 1.5 weeks), while tablet-treated cases delivered later (39.0 ± 1.4 weeks). This pattern suggests that more intensive treatment may be associated with prolonged gestation, although the relationship requires further investigation.
Extended ANOVA comparing normal pregnancies with GDM treatment subgroups showed significant differences in placental weight (F=3.627, p=0.018), neonatal birth weight (F=8.104, p<0.001), and gestational age (F=11.890, p<0.001). These findings indicate that treatment modality influences pregnancy outcomes and placental characteristics. Neonatal birth weight was significantly lower in the GDM group (2.6 ± 0.5 kg) compared to controls (2.9 ± 0.3 kg) (p=0.020).
Significant differences were observed in several key morphometric parameters between normal and GDM groups. The number of cotyledons was markedly elevated in GDM cases (21.3 ± 3.2) compared to normal pregnancies (14.6 ± 3.9) (p<0.001). Placental weight showed no significant difference between groups (684.27 ± 199.95 g in GDM vs. 682.57 ± 149.66 g in normal, p=0.81), but the placental weight across the GDM treatment groups and normal group shows a significant difference (p=0.012/p=0.049) (Table 1).
| Parameters | Normal (n=50) | GDM (overall) (n=20) | Diet controlled (n=5) | Oral-hypoglycemic (n=8) | Insulin treated (n=7) | ANOVA p-value |
|---|---|---|---|---|---|---|
| Cotyledon number | 14.56 ± 3.89 | 21.3 ± 3.21 | 20.80 ± 3.49 | 20.62 ± 3.11 | 22.29 ± 3.35 | 0.001 |
| Placental weight (gms) | 682.57 ± 149.66 | 684.27 ± 199.95 | 563.69 ± 143.11 | 724.70 ± 138.85 | 793.20 ± 235.08 | 0.049 |
| Placental thickness (cm) | 2.1 ± 0.46 | 2.66 ± 0.35 | 2.5 ± 0.46 | 2.6 ± 0.27 | 2.9 ± 0.38 | 0.007 |
The categorical variable analysis (site of attachment of cord and vascular patterns of the umbilical vessels) revealed a significant variation between GDM and Normal Pregnancies. Site of cord attachment showed significant differences (chi2=19.058, p=0.008), with GDM cases more commonly exhibiting eccentric cord insertion compared to normal pregnancies where it showed predominantly central insertion of the cord. Vascular pattern analysis demonstrated highly significant differences in both umbilical vein (chi2=52.519, p<0.001) and umbilical artery patterns (chi2=9.381, p=0.002). The GDM group exhibited magistral vascular patterns more predominantly than the dispersal pattern, while normal pregnancies exhibited dispersal patterns.
Quantitative histopathological analysis revealed striking differences between GDM and normal placentas across all measured parameters. The number of villi per high-power field was significantly increased in GDM cases (152.2 ± 17.2) compared to normal pregnancies (125.72 ± 8.273) (p=0.002). Villous diameter showed significant enlargement in GDM placentas (0.079 ± 0.0114 mm vs. 0.0552 ± 0.007 mm, p=0.01). Similarly, villous perimeter was significantly increased (0.33 ± 0.59 mm vs. 0.268 ± 0.018 mm, p=0.015), reflecting the overall enlargement of villous structures (Table 2).
| Parameters | Normal | Overall GDM | GDM (Diet-controlled) | GDM (oral-hypoglycemic agent) | GDM (Insulin-treated) | ANOVA p-value |
|---|---|---|---|---|---|---|
| Villi Count/HPF | 125.7200 ± 8.273 | 152.2 ± 17.2 | 140 ± 10 | 145 ± 12 | 152 ± 17.2 | 0.002 |
| Villous Diameter (mm) | 0.0552 ± 0.007 | 0.079 ± 0.0114 | 0.070 ± 0.01 | 0.075 ± 0.003 | 0.079 ± 0.0114 | 0.01 |
| Villous Perimeter (mm) | 0.268 ± 0.018 | 0.33 ± 0.59 | 0.290 ± 0.29 | 0.310 ± 0.015 | 0.331 ± 0.59 | 0.015 |
| Trophoblast Thickness (mm) | 0.0036 ± 0.0005 | 0.01 ± 0.002 | 0.006 ± 0.001 | 0.007 ± 0.0015 | 0.008 ± 0.002 | 0.005 |
| Capillary Count/Villus | 10 | 22 ± 2.5 | 18 ± 1.8 | 20 ± 2 | 22 ± 2.5 | 0.001 |
| Capillary Diameter (mm) | 0.0164 ± 0.0007 | 0.022 ± 0.01 | 0.018 ± 0.002 | 0.020 ± 0.003 | 0.022 ± 0.007 | 0.02 |
| Vessel Wall Thickness (mm) | 0.0153 ± 0.0004 | 0.031 ± 0.01 | 0.020 ± 0.003 | 0.025 ± 0.004 | 0.031 ± 0.009 | 0.008 |
Trophoblast thickness demonstrated the most dramatic difference, with GDM cases showing values of 0.01 ± 0.002 mm (0.008 ± 0.002 mm) compared to 0.0036 ± 0.0005 mm in normal pregnancies (p<0.001 / p=0.005). Vascular parameters also showed significant alterations, with capillary diameter increased in GDM cases (0.022 ± 0.01 mm vs. 0.0164 ± 0.0007 mm, p=0.02) and blood vessel wall thickness significantly elevated (0.031 ± 0.01 mm vs. 0.0153 ± 0.0004 mm, p=0.008).
Categorical histopathological analysis revealed several important differences between GDM and normal placentas. Syncytial knot formation was universally increased in GDM cases ('more' in 100% vs. 'less' in 100% of normal cases), indicating accelerated placental maturation and potential hypoxic stress (Figure 5 a&b). Chorangiosis, characterized by increased villous capillarization, was present in all GDM cases (100%) but absent in normal pregnancies (0%), supporting the concept of adaptive angiogenesis in response to metabolic stress (Table 3, Figure 6 a&b).
| Parameter | Normal (%) | GDM Diet (%) | GDM Tablet (%) | GDM Insulin (%) | Chi-square p-value |
|---|---|---|---|---|---|
| Syncytial Knots (More) | 0 | 100 | 100 | 100 | 0.0001 |
| Chorangiosis (Present) | 0 | 100 | 100 | 100 | 0.0001 |
| Villous Immaturity (Present) | 0 | 100 | 67 | 33 | 0.002 |
| Villous Edema (Present) | 0 | 50 | 33 | 33 | 0.01 |
| Fibrinoid Necrosis (Present) | 0 | 0 | 63 | 86 | 0.005 |
| Nucleated Fetal RBCs (Present) | 0 | 40 | 75 | 57 | 0.001 |
| Infarction (Present) | 0 | 100 | 100 | 100 | 0.0001 |
| Calcification (Present) | 25 | 40 | 40 | 40 | 0.45 |
The present study affirms that GDM induces consistent and measurable changes and abnormalities in placental morphometry (elevated cotyledon number, weight, thickness), vascular architecture (dominant magistral vein/artery patterns), and histopathological features. The Insulin-treated GDM cases exhibit the greatest deviations, suggesting a dose-response relationship between disease severity/intervention and placental remodeling [17,18].
Mean gestational age at delivery was significantly lower in GDM cases (37.8 ± 1.4 weeks) compared to normal pregnancies (39.2 ± 1.1 weeks) (p<0.001), which is in accordance with studies by George Daskalakis et al. [24]. This association may be due to chronic inflammation, oxidative stress, and altered prostaglandin metabolism in the diabetic environment.
Interestingly, our study found significantly lower neonatal birth weights in the GDM group (2.6 ± 0.5 kg) compared to controls (2.9 ± 0.3 kg) (p=0.020). This finding likely reflects the effectiveness of treatment interventions in preventing excessive fetal macrosomia, and possibly indicates a degree of growth restriction in some cases due to placental vascular compromise [25-27].
Number of cotyledons and thickness of placenta were significantly increased (approximately 46% higher than normal controls), consistent with previous reports [12,13,15]. In GDM patients the umbilical cord was eccentrically attached and exhibited predominantly magistral vascular distribution, reflecting adaptive responses to the altered metabolic environment [30-33].
Histopathological changes revealed significant increases in villous number, diameter, and trophoblast thickness, suggesting compensatory hypertrophy and hyperplasia in response to hypoxic stress [34-36]. Chorangiosis was uniformly observed in all GDM placentas (100%), serving as an adaptive angiogenic response to metabolic stress and hypoxia [17,37]. The analysis across different treatment modalities showed that diet-controlled cases delivered earliest and pharmacologically treated cases displayed more pronounced compensatory modifications [37,38].
Our comprehensive study provides significant insight into the morphometric and histopathological changes in the placenta of GDM pregnancies in comparison with normal pregnancies. The changes persist across GDM cases despite different treatment modalities and represent adaptive responses to the diabetic intrauterine environment. More severe changes were observed in insulin-treated patients. Routine placental assessment can help in stratifying perinatal risk and modulating treatment strategies in GDM patients.
Gestational Diabetes Mellitus
Obstetrics and Gynecology
Analysis of Variance
International Association of Diabetes and Pregnancy Study Groups
Statistical Package for the Social Sciences
The authors gratefully acknowledge the support of the Adichunchanagiri Institute of Medical Sciences and the Department of Anatomy and Department OBG for the contribution to sample collection and processing. We also thank the study participants and the laboratory staff whose cooperation made this research possible.