Introduction Stillbirth is a severe pregnancy complication. Maternal obesity is one of the most important modifiable risk factors of stillbirth, yet the biological mechanisms behind this association remain unclear. The adipose tissue is an endocrine organ which, in persons with obesity, causes a hyperinflammatory state. The aim of this study was to investigate inflammation as a contributing mechanism to the risk of stillbirth in women with obesity and if there are possible signs of different BMI phenotypes with different risk. Material and methods This was a case control study based on all cases of term singleton stillbirth without major fetal malformation in Stockholm County between 2002–2018. Placentas have been examined according to a standardized protocol. Placental inflammatory lesions were compared both between placentas from pregnancies with live born and stillborn infants with different class of body mass index (BMI) as well as among women with stillborn and live born infants with different classes of BMI, respectively. Results All inflammatory placental lesions were more common in placentas from women with stillbirth compared to placentas from women with live born infants. Vasculitis, funisitis and chronic villitis as well as overall fetal and maternal inflammatory response were present with a significantly increased proportion with increasing BMI in placentas from women with term stillbirth however, there were no differences between placentas from women in different BMI classes with term live born infants. Conclusion Both acute and chronic inflammatory placental lesions were more common in cases of stillbirth compared to pregnancies with live born infants. There were increased proportions of both acute and chronic placental inflammation (vasculitis, chronic villitis, funisitis and overall fetal and maternal inflammatory response) with increasing BMI among cases with term stillbirth, however no differences among controls with term live born infants.