Gestational age assessment by ultrasound cerebellar measurements in fetal and perinatal deaths

Background: Perinatal mortality remains high in low- and middle-income countries. Accurate assessment of fetal gestational age is crucial to distinguish between prematurity and intrauterine growth restriction, 2 conditions commonly associated with perinatal mortality that require different preventive strategies and management. Ultrasound measurements of the cerebellum have been shown to be accurate in assessing gestational age during pregnancy, but their postmortem performance has not yet been evaluated.

Objective: We aimed to explore the feasibility and validity of gestational age estimation in fetal and perinatal deaths by ultrasound measurements of the cerebellum.

Study design: This is an observational cross-sectional study. Between August 2020 and November 2022 postmortem cerebellar ultrasound measurements were conducted in a tertiary referral hospital in Barcelona, Spain. Extrauterine assessment included transcerebellar diameter, cerebellar vermis height, and cerebellar vermis length. Moreover, intrauterine ultrasound and autopsy direct cerebellar assessments were undertaken in a subset of cases. A total of 137 fetal and perinatal deaths [63 (46.0%) fetal deaths, 69 (50.4%) stillbirths, and 5 (3.6%) neonates] were included. First, we correlated different types of transcerebellar diameter measurements between them (intrauterine, extrauterine, and autopsy-based). Then, we evaluated the relationship between the extrauterine cerebellar ultrasound measurements and gestational age, and their performance across trimesters of gestation and in different central nervous system abnormalities.

Results: Gestational age ranged from 15.2 to 40.6 weeks. High correlation was observed between extrauterine, intrauterine, and autopsy transcerebellar measurements (P<.001) and between all extrauterine cerebellar measurements and gestational age (P<.001). Extrauterine transcerebellar diameter was identified as the strongest predictor of gestational age (coefficient of determination=0.88; P<.001), and its accuracy was not affected by the trimester of gestation, intrauterine growth restriction, or central nervous system alterations.

Conclusion: This study shows the feasibility and accuracy of postmortem gestational age evaluation by extrauterine ultrasound measurements of the cerebellum, especially of transcerebellar diameter. Implementation of this method as part of postmortem assessment could improve cause of death attribution, especially in resource-constrained settings.