Cell free hemoglobin in the fetoplacental circulation: a novel cause of fetal growth restriction?

What is it about?

The placenta is a barrier organ between mum's and baby's blood. It works to supply baby with the important substances for its growth whilst in the womb. Once nutrients and oxygen are carried across the placenta barrier, the blood vessels within the placenta must stay healthy and their surrounding muscle layer must remain relaxed. This ensures blood vessels remain wide-open, supplying adequate oxygenated and nutrient rich blood to the baby. A placental blood flow problem is one reason why babies fail to grow adequately in the womb. 5 to 8 out of every hundred babies are said to be "fetal growth restricted (FGR)". FGR babies are at increased risk of health problems in later life, including from high blood pressure, stroke and diabetes. Although serious, we don't know exactly why some placentas work better than others. We found that very underweight babies have a problem with a protein called "hemoglobin". Hemoglobin is normally present inside red blood cells, where it has a useful role in carrying oxygen. However, we know the placenta produces this molecule and release it directly into the fetal blood. In this form we have shown it is dangerous to the health of the baby's blood vessels. We have found that levels of "free haemoglobin" are raised in the blood of FGR babies. It inflames the cells that line the inside of the blood vessels and cause the blood vessels in the placenta to constrict, narrowing the bloods flow-stream and building up resistance to blood flow.

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