The 'Classes' of blood loss are a guide only. Women can react very individually to different amounts of blood loss or not react in the typical, physical way when related to the actual amount of blood lost. For example a woman may lose 400 to 500 mls after the birth but still feel very light headed and breathless, have a fast pulse and a low blood pressure. Another woman may lose 1000 mls or more and feel quite normal or unaffected. (Inaccuracies in blood loss estimation by the caregiver can also contribute to this).
The reaction of the woman will often depend on her body's physical state before the birth. Factors that can contribute to a woman not being able to tolerate a haemorrhage as well as another woman include:
A low haemoglobin level
Dehydrated during labour
A low haemoglobin level. This is the main reason for a woman not tolerating a heavy blood loss well. The woman's haemoglobin level (or the amount of red blood cells) is measured by a blood test called a 'Hb or Full Blood Count (FBC)' during the pregnancy. The red blood cells supply the woman's body with oxygen, including her heart, kidneys and brain (as well as to the baby during the pregnancy).
Abnormally low levels of red blood cells mean that the woman is anaemic (or iron deficient). Being anaemic can lead to the woman not physically tolerating even a 'normal' blood loss after the birth. You may wish to read more in
iron during the pregnancy.
Dehydrated during labour. If the woman becomes dehydrated during the labour, or is exhausted from a long labour, her body may not tolerate a haemorrhage well. She may physically react more sensitively to a normal, or slightly above average blood loss.