Placental insufficiency

Definition

• Placental insufficiency denotes inadequate placental perfusion that leads to an insufficient supply of oxygen and nutrients to the fetus; there is no universally accepted definition.
• It is understood as a progressive decline in placental function culminating in chronic fetal hypoxaemia and growth restriction.

Classification

• By time of diagnosis, early-onset (before 32 weeks) and late-onset growth restriction (from 32 weeks) are distinguished; the early form is usually more severe and often associated with pre-eclampsia.

Aetiopathogenesis

Physiology and pathophysiology

• Doppler sonography of the uterine arteries reflects the maternal side of placentation, particularly the remodeling of spiral arteries.
• Physiologically, there is a significant drop in resistance until about 24th week of gestation.
• Pathological findings include a pulsatility index (PI) above the 95th percentile and a persistent notch, an incisure post-systolic.

Clinical features

Clinical features and complications

• Placental insufficiency contributes to pre-eclampsia, fetal growth restriction, oligohydramnios and stillbirth.
• As an adaptation to hypoxaemia, blood flow is redistributed to vital organs (brain sparing), fetal movements decrease and growth slows.

Histology

• Typical histopathological findings are distal villous hypoplasia, increased syncytial knots, maternal vascular malperfusion, placental infarcts and fibrin deposition; there is no pathognomonic marker.

Diagnosis

Typical imaging findings

• Ultrasound: The waveform rises steeply and then falls, producing a clear incisure immediately after systole; only then does diastolic flow continue at a low level. The pattern repeats identically with every heartbeat.

• Classically, growth restriction is defined by an estimated fetal weight or abdominal circumference below the 10th centile; fetal mortality is highest below the 3rd centile.
• Diagnosis relies mainly on ultrasound biometry and Doppler velocimetry, especially of the umbilical artery.

Keep learning in the app

Further reading (selection)

1. StatPearls: Placental Insufficiency (NCBI Bookshelf)
2. StatPearls: Fetal Growth Restriction (NCBI Bookshelf)
3. DocCheck Flexikon, Arteria uterina

Cross-references