What is Chronic Histiocystics Intervillositis (CHI)?

The immune system launches an attack on the placenta which then gets clogged up by histiocyte cell 'junk' that the mother fires into the intervillous space (the space in between the finger‐like vessels placenta). Normally the baby will not know this is happening unless the problem is untreated for four weeks. In a normally functioning placenta the space should be full of free flowing nutrient‐rich blood, which then flows to baby after an 'attack' it becomes a car park of histiocytic junk. To understand where all these bits are please have a look at the following diagrams:

  • Umbilical cord
  • Amnion
  • Chorionic plate
  • Intervillous space (maternal blood)  
  • Basal plate
  • Cotyledon
  • Villus

Courtesy of http://www.merckmanuals.com/home/women-s-health-issues/drug-use-during-pregnancy/drug-use-during-pregnancy

What does this mean?

If the attack goes untreated it results in insufficient blood flow to the baby, hence reverse Dopplers or Reverse End Diastolic flow. Reverse flow normal indicates the need for immediate delivery, leaving a baby in the womb with this finding means the baby is conserving all the blood it does receive and trying to direct it to vital organs, in a bid to survive. Everything is sent to the brain and heart, but this is unlikely to be enough and is sure to result in brain and heart damage. This is also why the fluid levels drop, (often expressed as Oligohydramnios or anhydramnios) as the baby stops urinating.