Missed abortion in the 11-21-week period: Fetal autopsy and placental histopathological analysis of 794 cases.

INTRODUCTION: Missed abortion (MA) is a type of miscarriage with multiple etiological factors that refers to fetal death with a failure of the retained intrauterine product of conception to be discharged spontaneously. Currently fetal death in missed abortion is categorized according to three main causes: Fetal, placental, and maternal factors. The aim of the current study was to contribute and increase knowledge in clinical practice of late first and second trimester MA (Gestational age: week 11 + 0 - week 20 + 6).

MATERIAL AND METHODS: This retrospective case series study includes 794 cases of fetuses and matching placentas sent to the Section of Perinatal Pathology, Department of Pathology, Karolinska Hospital between 2003 and 2019 from five different gynecology departments in the Stockholm region, Sweden.

RESULTS: The cases were divided into two groups according to gestational length; gestational week 11 + 0-14 + 6 (group A) and 15 + 0-20 + 6 (group B) respectively, and comparisons were made between groups. Fetal growth restriction and placental pathology were more common in late MA, but number of cases with malformation were higher in early MA. Cord pathology was seen in approximately 40 % of the cases and equally distributed in the gestational weeks included.

DISCUSSION: Fetal growth restriction and placental pathology were more common in late second trimester MA. This might demonstrate an early placental dysfunction affecting fetal growth and may be associated to maternal comorbidity such as autoimmune disease and cardiovascular disease. It is advisable to investigate maternal factors more closely after late second trimester MA before a future pregnancy. The risk for recurrent MA is believed to be low in cases of significant cord pathology.

CONCLUSION: Cord complications were over-represented in missed abortion suggesting a probable etiopathogenetic link to fetal demise in this condition.