THICK PLACENTA

MEASUREMENT OF PLACENTAL THICKNESS

• Measure perpendicular to the basal and chorionic plates, in the mid portion of the placenta (usually near the cord insertion) (1).

• Normal placental thickness rarely exceeds 4 cm (1).
• Beware of fundal or lateral placental location in order to avoid measuring placental thickness in a tangential section.

• Avoid including a myometrial contraction in the measurement.
• Amount of amniotic fluid bears a relationship to apparent placental thickness. Oligohydramnios may artificially increase thickness whereas polyhydramnios may decrease the thickness.

CAUSES OF A THICK PLACENTA

• Homogeneous thickening:
• Idiopathic.
• Maternal diabetes mellitus.
• Non immune and immune hydrops.
• Infection.
• Aneuploidy (trisomy).
• Fetal or maternal anemia.
• Heterogeneous thickening:
• Placental hemorrhage.
• Molar pregnancy.
• Triploidy.
• Villitis.
• Beckwith-Wiedermann syndrome.
• Focal thickening:
• Placental tumor.
• Breus' mole.
• Placental abruption.
• Focal placental hemorrhage.

Reported to occur in 0.6% of pregnancies.

OUTCOME

• Thick placentas, even when isolated, are associated with an increased perinatal morbidity and mortality (1). The majority of perinatal deaths are associated with anomalies, non-immune hydrops, placental abruption and premature rupture of membranes.
• There is no evidence on whether increasing thickness is associated with poorer outcome.

REFERENCES

1. Dombrowski MP, Wolfe HM, Saleh A et.al. The sonographically thick placenta: a predictor of increased perinatal morbidity and mortality. Ultrasound Obstet Gynecol 1992;2:252-255.