Intrauterine Fetal Demise

Intrauterine fetal demise, commonly called stillbirth, is the death of a fetus in the uterus at or after a defined threshold of gestational age. It is among the most consequential adverse outcomes in obstetrics, and a substantial proportion of cases remain unexplained despite systematic evaluation.

Definition

Intrauterine fetal demise is the death of a fetus before complete expulsion or extraction from the mother at or beyond a specified gestational-age or birthweight threshold, with thresholds varying between definitions used internationally (for example 20 or 28 completed weeks); below the relevant threshold the loss is classified as miscarriage rather than stillbirth.

Scope

The entry covers the definition and gestational-age thresholds used for stillbirth, its principal risk factors and causal categories, the diagnostic confirmation of fetal death, and the rationale for systematic post-loss evaluation. It is a reference topic and does not provide guidance on the management of an affected pregnancy.

Core questions

• How is stillbirth defined and why do gestational-age thresholds vary?
• What are the major risk factors and causal categories for fetal death?
• How is intrauterine fetal demise diagnosed?
• Why does a large share of stillbirths remain unexplained?

Key concepts

• Stillbirth definition and gestational-age thresholds
• Antepartum versus intrapartum fetal death
• Placental causes
• Unexplained stillbirth
• Risk factors (maternal age, obesity, smoking, growth restriction)
• Post-loss evaluation (autopsy, placental examination, genetic testing)

Mechanisms

Stillbirth is a final common endpoint of diverse pathways. Major categories include placental dysfunction and insufficiency (often manifesting as fetal growth restriction), maternal conditions such as hypertensive disease and diabetes, fetal chromosomal and structural anomalies, infection, and umbilical cord events. Many of the strongest population-level risk factors, including advanced maternal age, obesity, smoking, and small-for-gestational-age fetuses, act in part through impaired placental function (Flenady et al., 2011). Despite thorough evaluation, a considerable proportion of cases have no identified cause, which is why systematic post-loss assessment is emphasized (ACOG, 2020).

Clinical relevance

Understanding stillbirth and its risk factors underlies antenatal surveillance aimed at recognizing fetal compromise and structures the evaluation that follows a loss. This entry describes definitions, risk factors, and causal categories; it is not a basis for individual decisions about surveillance or the management of a pregnancy or bereavement.

Epidemiology

Stillbirth remains a major global burden, with millions of cases annually and rates many times higher in low- and middle-income countries than in high-income settings; the disparity and the slow pace of decline have been documented in global analyses (Lawn et al., 2016). Even in high-income countries, identifiable risk factors explain only part of the variation in risk (Flenady et al., 2011).

Evidence & guidelines

Systematic reviews have quantified the major risk factors for stillbirth in high-income countries (Flenady et al., 2011) and characterized global rates and trends (Lawn et al., 2016). A large case-control study of stillbirths described associations present at pregnancy confirmation (Stillbirth Collaborative Research Network, 2011), and ACOG provides consensus guidance on the systematic evaluation of stillbirth (ACOG, 2020).

History

Definitions of stillbirth have long varied across jurisdictions by gestational-age and birthweight thresholds, complicating comparison. Recent decades have brought standardized causal classification systems, large multicenter studies of risk factors, and global initiatives that placed stillbirth, historically underrepresented in mortality statistics, on the agenda for reduction by 2030 (Lawn et al., 2016).

Debates

How should stillbirth be defined for comparison?

Gestational-age and birthweight thresholds differ between countries and surveillance systems, so reported rates are not directly comparable and a substantial fraction of losses near the threshold are classified inconsistently, complicating international monitoring.

Seminal works

• flenady-2011
• lawn-2016

Frequently asked questions

What is the difference between stillbirth and miscarriage?

The distinction is one of gestational age: a fetal death at or beyond a defined threshold (such as 20 or 28 completed weeks, depending on the definition used) is classified as stillbirth, while a loss before that threshold is termed miscarriage.

Why are so many stillbirths called unexplained?

Even after systematic evaluation including placental examination, autopsy, and genetic testing, a notable proportion of stillbirths have no single identifiable cause, reflecting both the multifactorial nature of fetal death and limits in current diagnostic understanding.