What are the common maternal, fetal, and placental causes of intrauterine death?

Causes of Intrauterine Death

Placental pathologies are the predominant cause of intrauterine fetal death, accounting for approximately 65% of cases, followed by fetal anomalies, infections, and maternal conditions, with a significant proportion remaining unexplained.

Placental Causes (Most Common)

Placental abnormalities represent the single largest category of intrauterine death causes and are the most critical focus for investigation 1, 2.

Maternal Vascular Malperfusion (MVM)

• Most frequent placental pathology causing intrauterine death, accounting for 30-34% of cases 3
• Peaks in early third trimester (24-32 weeks gestation) 1, 3
• Includes placental bed pathology, which occurs in 33.6% of all fetal deaths with highest occurrence between 24-32 weeks 1
• Strongly associated with preeclampsia and hypertensive disorders 4
• Often presents with intrauterine growth restriction (IUGR) in 37.9% of cases 1

Developmental Placental Pathology

• Contribution increases significantly after 32 weeks of gestation 1
• Accounts for 17.6% of fetal deaths overall 1

Umbilical Cord Complications

• Represent 5.2% of intrauterine deaths 1
• Frequency increases after 32 weeks gestation 1

Combined Placental Pathologies

• Account for 5.4% of cases, often involving both maternal and fetal vascular malperfusion (10% when combined) 1, 3

Fetal Vascular Malperfusion (FVM)

• Occurs in 6% of cases as exclusive cause 3
• Can coexist with maternal vascular pathology 3

Placental Parenchyma Pathology

• Less frequent, accounting for 3.1% of cases 1

Specific Rare Placental Pathologies

• Chronic histiocytic intervillositis and massive perivillous fibrin deposition represent 2% of cases 2
• These specific pathologies have high recurrence rates and can only be diagnosed microscopically 2

Fetal Causes

Chromosomal and Congenital Anomalies

• Account for approximately 20% of fetal growth restriction cases leading to death 4
• Congenital malformations represent 5.3% of intrauterine deaths 1
• More prevalent at earlier gestational ages 5

Fetal Growth Restriction

• Fetuses with estimated fetal weight below 10th percentile have stillbirth rate of approximately 1.5% (twice the rate of normal growth) 4
• Below 5th percentile, stillbirth rate reaches 2.5% 4
• Worst outcomes occur with estimated fetal weight less than 3rd percentile or with Doppler abnormalities 4

Maternal Causes

Substance Use Disorders

• Tobacco use increases risk through placental abruption, placenta previa, fetal growth restriction, and preterm premature rupture of membranes 4
• Cocaine and methamphetamine increase risk via severe hypertension and cardiovascular complications 4
• Intravenous opiate use increases maternal infection morbidity (HIV, hepatitis C, endocarditis, sepsis) 4

Pre-existing Medical Conditions

• Hypertension and diabetes are major risk factors when present pre-gestationally 5
• Chronic hepatitis (HBV and HCV) with cirrhosis increases maternal and perinatal mortality 4

Maternal Demographics and Obstetric History

• Maternal overweight, advanced maternal age, and smoking are major risk factors 5
• Multiple prior cesarean deliveries increase risk through placenta accreta spectrum and hemorrhagic complications 4
• Short interpregnancy intervals (<18 months) increase morbidity and mortality, particularly in women >35 years 4

Infectious Causes

Ascending Infection

• Accounts for 19% of intrauterine deaths overall 2
• Peaks at 22 weeks gestation 2
• Significantly more common in Black mothers compared to other ethnicities 2
• Overall infectious causes represent 1.9% of cases 1

Gestational Age-Specific Patterns

Early Preterm (<34 weeks)

• Placental causes and unknown etiology most dominant (34.8% and 41.7% respectively) 1
• Ascending infection peaks around 22 weeks 2

Late Preterm (34-37 weeks)

• Placental causes increase to 77.6% 1
• Unknown causes decrease to 16.5% 1

Term (>37 weeks)

• Idiopathic causes become most common 3
• Developmental placental pathology increases 1

Unexplained Cases

• Represent 23.1% of intrauterine deaths despite comprehensive evaluation 1
• Rate decreases with advancing gestational age 1
• Many unexplained cases have placental histological lesions of uncertain significance 2

Critical Diagnostic Consideration

Placental histological examination is the single most useful component of the autopsy process for determining cause of intrauterine death 2. Fetal autopsy remains the gold standard, but post-mortem MRI can be offered when autopsy is refused 5. The combination of placental examination, fetal autopsy, and maternal clinical evaluation provides the most comprehensive assessment 6.