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Maternal Blood Volume. During pregnancy the plasma volume increases by 40-50% and the red blood cell volume increases only by 20–30%. [22] These changes occur mostly in the second trimester and prior to 32 weeks gestation. [24] Due to dilution, the net result is a decrease in hematocrit or hemoglobin, which are measures of red blood cell ...
Pregnant women need almost twice as much iron as women who are not pregnant do. Not getting enough iron during pregnancy raises risk of premature birth or a low-birth-weight baby. [23] Hormonal changes in the pregnant woman result in an increase in circulating blood volume to 100 mL/kg with a total blood volume of approximately 6000–7000 mL.
As the amniotic fluid builds up in the lungs, the patient may begin to exhibit signs of pulmonary hypertension due to the fluid blocking the blood flow of the lungs and decreasing the oxygen. [4] As the amniotic fluid embolism progresses the final stage before cardiovascular collapse involves hemorrhaging or large volume blood loss. [5]
It is estimated that less than 1ml of fetal blood is lost to the maternal circulation during normal labour in around 96% of normal deliveries. [1] [2] The loss of this small amount of blood may however be a sensitising event and stimulate antibody production to the foetal red blood cells, an example of which is Rhesus disease of the newborn.
[4] [5] Causes of bleeding after childbirth include poor contraction of the uterus, retained products of conception, and bleeding disorders. [4] About 8.7 million cases of severe maternal bleeding occurred in 2015 [2] resulting in 83,000 deaths. [3] Between 2003 and 2009, bleeding accounted for 27% of maternal deaths globally. [6]
While an early study suggested that maternal red blood cells switch on hemoglobin F production during pregnancy, [27] more recent literature suggested that the increase in haemoglobin F could be, at least in part, due to fetal red blood cells being transferred to the maternal circulation. [28] [21]
[2] [4] A study of more than 200,000 women came to the result that admission to inpatient care during pregnancy was associated with an 18-fold increase in the risk of venous thromboembolism (VTE) during the stay, and a 6-fold increase in risk in the four weeks after discharge, compared with pregnant women who did not require hospitalization. [5]
Vasa praevia is a very rare, presenting only 4:10,000 cases from the largest study of the condition. [16] Risks of antepartum bleeding due to vasa praevia greatly increase during the third trimester of pregnancy during cervical dilation or placenta praevia.