Foetal cerebral redistribution

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Artist's depiction of a foetus at 38 weeks' gestation 40 weeks pregnant.png
Artist's depiction of a foetus at 38 weeks' gestation

Foetal cerebral redistribution or 'brain-sparing' is a diagnosis in foetal medicine. It is characterised by preferential flow of blood towards the brain at the expense of the other vital organs, and it occurs as a haemodynamic adaptation in foetuses which have placental insufficiency. [1] The underlying mechanism is thought to be vasodilation of the cerebral arteries. [2] Cerebral redistribution is defined by the presence of a low middle cerebral artery pulsatility index (MCA-PI). Ultrasound of the middle cerebral artery to examine the Doppler waveform is used to establish this. [3] Although cerebral redistribution represents an effort to preserve brain development in the face of hypoxic stress, it is nonetheless associated with adverse neurodevelopmental outcome. [1] The presence of cerebral redistribution will be one factor taken into consideration when deciding whether to artificially deliver a baby with placental insufficiency via induction of labour or caesarian section.

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 electronic monitoring, even if there is no other evidence of reduced blood flow to the placenta, normal uterine blood flow rate being 600mL/min.

Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstriction, which is the narrowing of blood vessels.

Cerebral arteries

The cerebral arteries describe three main pairs of arteries and their branches, which perfuse the cerebrum of the brain. The three main arteries are the:

Additional images

An example of the use of Doppler ultrasound to examine the waveform within an artery; this technique is applied to the middle cerebral artery to diagnose cerebral redistribution SpectralDopplerA.jpg
An example of the use of Doppler ultrasound to examine the waveform within an artery; this technique is applied to the middle cerebral artery to diagnose cerebral redistribution

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Ventriculomegaly Cerebral ventricle enlargement

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Percutaneous umbilical cord blood sampling

For other uses see PUBS

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Cervical pregnancy

A cervical pregnancy is an ectopic pregnancy that has implanted in the uterine endocervix. Such a pregnancy typically aborts within the first trimester, however, if it is implanted closer to the uterine cavity – a so-called cervico-isthmic pregnancy – it may continue longer. Placental removal in a cervical pregnancy may result in major hemorrhage.

Breus' mole is a massive, subchorionic, tuberous hematoma, formed out of maternal blood in the uterus in pregnancy. It was first described by Karl Breus in 1892.

References

  1. 1 2 Eixarch E, Meler E, Iraola A, et-al. Neurodevelopmental outcome in 2-year-old infants who were small-for-gestational-age-term fetuses with cerebral blood flow redistribution. Ultrasound Obstet Gynecol. 2008; 32(7): 894-9. PMID   19035538
  2. Skandhan, Avni; Knipe, Henry. "Fetal head sparing theory". Radiopaedia.
  3. Hershkovitz R, Kingdom JC, Geary M, Rodeck CH. Fetal cerebral blood flow redistribution in late gestation: identification of compromise in small fetuses with normal umbilical artery Doppler. Ultrasound Obstet Gynecol. 2000; 15(3): 209-12. PMID   10846776