Placental insufficiency or utero-placental insufficiency is the failure of the placenta to deliver sufficient nutrients to the fetus during pregnancy, and is often a result of insufficient blood flow to the placenta. The term is also sometimes used to designate late decelerations of fetal heart rate as measured by cardiotocography or an NST, even if there is no other evidence of reduced blood flow to the placenta, normal uterine blood flow rate being 600mL/min. Causes
The following characteristics of placentas have been said to be associated with placental insufficiency, however all of them occur in normal healthy placentas and full term healthy births, so none of them can be used to accurately diagnose placental insufficiency:
Abnormally thin placenta (less than 1 cm)
Circumvallate placenta (1% of normal placentas)
Amnion cell metaplasia, (amnion nodosum) (present in 65% of normal placentas)
Increased syncytial knots
Calcifications
Infarcts due to focal or diffuse thickening of blood vessels
Villi capillaries occupying about 50% of the villi volume or when <40% of capillaries are on the villous peripheryPlacental insufficiency should not be confused with complete placental abruption, in which the placenta separates off the uterine wall, which immediately results in no blood flow to the placenta, which leads to immediate fetal demise. In the case of a marginal, incomplete placental abruption of less than 50%, usually weeks of hospitalization precedes delivery and outcomes are not necessarily affected by the partial abruption. Pathophysiology
Maternal effects
Several aspects of maternal adaptation to pregnancy are affected by dysfunction of placenta. Maternal arteries fail to transform into low-resistance vessels (expected by 22–24 weeks of gestation).
Diagnosis
The following tests have been promoted as supposedly diagnosing placental insufficiency, but all have been unsuccessful at predicting stillbirth due to placental insufficiency:
Placental grading
Amniotic fluid index
Fetal biophysical profile test scoring
Doppler velocimetry
Routine ultrasound scanning
Detection and management of maternal diabetes mellitus
Antenatal fetal heart rate monitoring using cardiotocography
Vibroacoustic stimulation, fetal movement counting
Home vs. hospital-based bed rest and monitoring in high-risk pregnancy
In-hospital fetal surveillance unit
Use of the partograph during labor
Cardiotocography during labor with or without pulse oximetry

See also
Small for gestational age

References


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