Intrauterine Death Definition by Gestational Age
Intrauterine death (fetal demise) is defined as death of the fetus occurring at or after 20 completed weeks of gestation. 1
Standardized Terminology
The term "intrauterine fetal death" (IUFD) or "stillbirth" specifically applies to fetal demise occurring after 20 completed weeks of gestational age, as established by international consensus guidelines. 1, 2
Key Gestational Age Thresholds
- Before 20 weeks: Spontaneous loss is classified as miscarriage, not intrauterine death 1
- At or after 20 weeks: Fetal death is classified as stillbirth or intrauterine fetal death 1, 2
Diagnostic Criteria
Stillbirth is confirmed when the fetus shows no evidence of life after complete expulsion or extraction from the mother after 20 completed weeks of gestation, including: 1
- Absence of breathing
- No heartbeat
- No umbilical cord pulsation
- No definite movement of voluntary muscles
Alternative Weight Criterion
A birth weight of 350 grams or more can be used to define stillbirth if gestational age is unknown. 1
Clinical Context
The 20-week threshold is clinically significant because it represents the approximate boundary of fetal viability, though actual survival rates remain extremely poor until later gestational ages. 1, 3
Periviable Period Considerations
- 20-22 weeks: Survival rate is 5-6% with near-universal serious morbidity 1, 3
- 23 weeks: Survival rate remains 23-27% 1
- 24-25 weeks: Survival improves to 42-76% 1, 3
Epidemiology
Intrauterine fetal death complicates approximately 1% of pregnancies after 20 weeks of gestation, with an incidence rate of approximately 12 per 1000 births. 4, 5
Common Risk Factors
The most frequently identified maternal conditions associated with IUFD include: 2, 5
- Hypertensive disorders (pregnancy-induced hypertension, preeclampsia) - most common identifiable cause
- Antepartum hemorrhage (placental abruption, placenta previa)
- Gestational diabetes mellitus and obesity
- Placental pathology (infarction, infections) - found in over 80% of cases on histopathology
Important Caveat
Approximately 50% of intrauterine fetal deaths remain unexplained despite thorough investigation, though specialized testing (karyotype, infectious workup, fetomaternal hemorrhage assessment, thrombophilia screening) may identify additional causes. 4