Blood flow to placenta

  • #1
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Main Question or Discussion Point

Hi there, I wondered if someone with a good knowledge of medicine/human biology could help me - this may sound like a very silly question but I don't know enough about biology to know for sure! I am 25 weeks pregnant with twins and accidentally fell asleep with a hair tie around my wrist. When I woke up, the hair tie was very tight and the skin underneath was red and purple and sore. My hand looked normal though, no pins and needles or anything. I am worried that this could have cut off blood supply to the babies and caused them brain damage or something - can you give me any information to help put my mind at rest? Thank you!
 

Answers and Replies

  • #2
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Just to clarify, I'm not after medical advice - I just want to know if it would be medically/scientifically possible for cutting off circulation like this to affect placental blood flow.
 
  • #3
Pythagorean
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No, most blood vessel systems are "in parallel" so if you were to cut off circulation to one section it would mean more pumping pressure for the otuer systems:

After limb exsanguination and tourniquet inflation, there is an increase in systemic vascular resistance and an effective increase in circulating blood volume. This leads to an increase in central venous pressure and in most instances an accompanying increase in systolic arterial pressure, both of which are usually transient. Application of bilateral thigh tourniquets can increase the effective circulating blood volume by up to 15% (∼750 ml in an adult). Such large increases in circulating blood volume may cause large and sustained increases in central venous pressure and circulatory overload. Cardiac failure and cardiac arrest have been reported after the application of bilateral thigh tourniquets. Following the initial transient increase in arterial pressure, it is common to see a second, gradual increase in arterial pressure. This is thought to accompany the development of tourniquet pain and develops a variable period of time after inflation.
http://m.ceaccp.oxfordjournals.org/content/9/2/56.full

Further, the placenta has alot going on with regard to blood flow. The uteran circulatory system is "rewiring" itself, and throughout the trimesters, the rate of flow changes a lot. Notice, also, that the placenta is actually two circulatory systems (or in your case, three). Here's an overview of placental circulation:

http://www.ncbi.nlm.nih.gov/books/NBK53254/#!po=7.57576
 
  • #4
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You can visit a local clinic to have your baby health checked up over PI at anytime. I think all moms should.
 
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  • #5
You have nothing to be concerned about.

Firstly an artery by definition carries blood from the heart to the tissues and a vein is a vessel that returns blood back the the heart, for this following explanation don't consider blood flow to the lungs.

Blood flow from the left heart carries oxygen rich blood via the arteries to the body tissues.

The main artery carrying oxygen coming from the heart is called the aorta. The blood supply to the wrist is via the thoracic aorta->subclavian artery->radial and ulnar 'wrist' arteries) this is not connected to the blood supply to the uterus (which is from the uterine artery which derives its supply off the aorta further down in the pelvis).

There can be no direct consequence that reduced wrist circulation could cause reduced placental flow to the baby.

The hair tie may have slightly reduced venous blood flow returning blood back to the heart from the arm hence the purple appearance of backed up wrist blood, the arteries are under much x5 higher pressure hence the arterial pressure was higher that the pressure exerted by the band on the wrist. If wrist arterial supply had of been reduced you would have been woken with pain, discomfort and pins and needles.

There is no connection with blood supply to the arm and blood supply to your baby with what you describe.

I would be more worried about the effects of drinking and smoking to the baby.

The effect of an arterial tourniquet did not happen in your situation. You never reduced the arterial blood supply to your wrist, at worst you only slightly reduced the venous return back to your arm.

Interestingly during pregnancy you increase the cardiac output from the heart and your vascular resistance to blood flow falls at a tissue level, your hemoglobin levels also fall a little.
 

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