Effect of Increased Prepregnancy Body Mass Index on Placental Morphologic Features in Gestational Diabetes

Introduction: Gestational Diabetes Mellitus (GDM) and obesity are both independent and associated risk factors that complicate pregnancy. There has been a worldwide increase in the incidence of GDM. This has been explained by the global epidemic of obesity which has, in turn, resulted in an increase in number of pre-obese and obese women of reproductive age group. Both conditions are associated with metabolic and functional disturbances that affect the placenta. The gross morphologic alterations in gestational diabetic placentae have been extensively studied. The morphopathologic impact of obesity on the gestational diabetic placenta is yet to be explored. Aim: The aim of the present study was to evaluate the changes in placental morphology of GDM pregnancies as compared to placentae from normoglycaemic, normal prepregnancy Body Mass Index (BMI) pregnancies and to further assess the effect of high prepregnancy BMI on the placentae of GDM in comparison with the placentae of GDM with normal prepregnancy BMI. Materials and Methods: The observational cross-sectional comparative study was carried out among women who attended three specialty obstetric clinics in an urban city in central Tamil Nadu, India. The study was carried out between May to August 2016. A total of 95 women, of whom 65 were gestational diabetic participated in the study. The control group comprised of 30 women who had normal prepregnancy BMI and who were normoglycaemic throughout pregnancy. BMI was calculated from the prepregnancy weight and height. Using Indian standards of BMI classification, the GDM women were grouped into Lean GDM (LG; n=30) and Obese GDM (OG; n=35). At term, the placentae were collected after the delivery from both study and control groups and analysed for gross morphological parameters including placental weight, volume, thickness, diameter, shape and size, number of cotyledons and site of cord insertion. Statistical test ANOVA with post-hoc analysis was used to compare the groups and Pearson's coefficient was used to correlate BMI with placental parameters, using the Statistical Package for Social Sciences (SPSS) version 21.0.0, IBM. Results: Placental weight, volume, thickness and diameter showed a significant increase in the GDM group as compared to control group. There were a higher proportion of irregular placental shapes and marginal and velamentous cord insertion among gestational diabetic placentae. Placental weight, volume and thickness were significantly increased in OG placentae as compared to LG. Pearson's r showed a weak however, significant positive correlation between maternal prepregnancy BMI and placental weight, volume and thickness. Conclusion: Maternal prepregnancy BMI influences gross morphological features of the placenta. The finding is relevant in the context of understanding the response of the placenta to obesity and GDM and in evolving ultrasonographic placental examination criteria that can be used to monitor and safeguard against adverse pregnancy outcomes.