Risk factors for sudden intrauterine unexplained death: epidemiologic characteristics of singleton cases in Oslo, Norway, 1986-1995.
OBJECTIVE
The epidemiologic characteristics of unexplained stillbirths are largely unknown or unreliable. We define sudden intrauterine unexplained death as a death that occurs antepartum and results in a stillbirth for which there is no explanation despite postmortem examinations, and we present risk factors for this type of stillbirth in singleton gestations.


METHODS
Singleton antepartum stillbirths (n = 291) and live births (n = 582) in Oslo were included and compared with national data (n = 2025 and n = 575,572, respectively). Explained stillbirths (n = 165) and live births in Oslo served as controls for the cases of sudden intrauterine unexplained death (n = 76) in multiple logistic regression analyses.


RESULTS
One fourth of stillbirths remain unexplained. The risk of sudden intrauterine unexplained death (1/1000) increased with gestational age, high maternal age, high cigarette use, low education, and overweight or obesity. Primiparity and previous stillbirths or spontaneous abortions were not associated with sudden intrauterine unexplained death.


CONCLUSIONS
Risk factors for sudden intrauterine unexplained death are identifiable by basic antenatal care. Adding unexplored stillbirths to the unexplained ones conceals several risk factors and underlines the necessity of a definition that includes thorough postmortem examinations.
Department of Obstetrics and Gynecology, the Institute of Forensic Medicine, and the Section for Clinical Epidemiology, The National Hospital, University of Oslo, Norway.
J F
JF
Frøen
M
M
Arnestad
K
K
Frey
A
A
Vege
O D
OD
Saugstad
B
B
Stray-Pedersen
D000022:Abortion, Spontaneous; D000328:Adult; D004522:Educational Status; D005260:Female; D005313:Fetal Death / Q000453:epidemiology* / Q000209:etiology; D005865:Gestational Age; D006801:Humans; D008423:Maternal Age; D009664:Norway / Q000453:epidemiology; D009765:Obesity / Q000150:complications; D016017:Odds Ratio; D010298:Parity; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D011295:Prenatal Care; D012042:Registries; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects