The etiology of stillbirth over 30 years: a cross-sectional study in a tertiary referral unit.

INTRODUCTION Stillbirth remains an often unpredictable and devastating pregnancy outcome, and despite thorough investigation, the number of stillbirths attributable to unexplained causes remains high. Placental examination has become increasingly important where access to perinatal autopsy is limited. We aimed to examine causes of stillbirth in normally formed infants over 30 years and whether a declining autopsy rate has affected our ability to determine a cause for stillbirths. MATERIAL AND METHODS All cases of normally-formed singleton infants weighing ≥500g, which died prior to the onset of labour from 1989 - 2018 were examined. Trends for specific causes and uptake of perinatal autopsy were analysed individually. RESULTS 229,641 infants were delivered, with 840 stillbirths giving a rate of 3.66/1000. The rate of stillbirth declined from 4.84/1000 in 1989 to 2.51 in 2018 (p < .001). There was no difference in the rate of stillbirth between nulliparous and multiparous women (4.25 vs 3.66 per 1000, p = .026). Deaths from placental abruption fell (1.13/1000 in 1989 to 0 in 2018, p < .001), and the relative contribution of placental abruption to the incidence of stillbirth also fell, from 23.3% (7/30) in 1989 to 0.0% (0/19) in 2018 (p < .001). Stillbirth attributed to infection remained static (0.31/1000 in 1989 to 0.13 in 2018, p = .131), while a specific causal organism was found in 79.2% (42/53) of cases. Unexplained stillbirths decreased from 2.58/1000 (16/6200) in 1989 to 0.13 (1/7581) in 2018 (p < .001), despite a fall in the uptake of perinatal autopsy (96.7% (29/30) in 1989 to 36.8% (7/19) in 2018; p < .001). Placental disease emerged as a significant cause of stillbirth from 2004 onwards (89.5% (17/19) in 2018). CONCLUSIONS The present analysis is one of the largest single-centre studies on stillbirth published to date. Stillbirth has fallen across the study period across parity. A decrease in deaths secondary to placental abruption has contributed largely to this. Infection-related deaths are static, however, in one-fifth of cases a causative organism was not found. Despite a decreasing autopsy rate, unexplained stillbirths continue to fall as the importance of placental pathology is increasingly recognised.