Why is a decrease in hematocrit during pregnancy, and what values ​​are acceptable?

Blood test

Hematocrit (in laboratory forms Ht, HCT) shows the relative volume of red blood cells (erythrocytes) in the blood. Hematocrit is not a standard blood test, it is prescribed separately and does not provide information on the amount of hemoglobin and the variability of the form of red blood cells.

Hematocrit is determined by dividing blood into fractions in a centrifuge

The blood of a healthy person consists of plasma (60%) and blood cells (40%), among which erythrocytes are 99%.


  • Hematocrit during pregnancy
    • Low hematocrit
  • Elevated hematocrit
  • Normalization of Ht in pregnancy

Hematocrit during pregnancy

During pregnancy as the fetus grows, the blood system of the expectant mother undergoes natural physiological changes that are aimed at adapting to an increase in fluid volume, increased demand for erythrocytes. If the hematocrit is lowered during pregnancy is insignificant, then this is a normal process. It is not pathology and requires only constant monitoring. This condition is called the physiological decline of the hematocrit.

Low hematocrit

If a woman before pregnancy had diagnosed or latent pathologies (anemia), then during fetal gestation they become aggravated and cause a pathological lowering of the hematocrit.

The dynamics of the physiological decrease in the relative level of red blood cells in pregnant women is gradual and peaks to the third trimester. This is mainly due to the increase in blood volume due to an increase in the amount of plasma. The absolute level of red blood cells is also increased, but the process of their production does not keep up with the rapid increase in blood volume.

In pregnant women the norm of Ht readings is from 32 to 36%

By the end of the third trimester the blood volume reaches its maximum values, the growing fetus requires more and more oxygen, so Ht can decrease to the minimum values.

If the hematocrit is reduced to 32% or less, this condition threatens the normal development of the fetus, and therapy is needed to increase hematocrit and prevent iron deficiency anemia. In such cases, additional blood tests are performed to evaluate the red blood cells and the hemoglobin content.

Table Ht in the blood

In 90% of cases low hematocrit during pregnancy becomes a consequence of developed iron deficiency anemia.

Another reason for the pathological decline of Ht can be such diseases:

  • kidney failure;
  • toxic and infectious hepatitis;
  • Relapses of gastrointestinal diseases (enterocolitis, gastric ulcer), as a result of which there is a loss of hemoglobin and impaired absorption of iron in the digestive tract;
  • infections and autoimmune reactions.

An important factor is considered to be malnutrition and the use of large volumes of free fluid.


In a state where Ht is lowered, the cells of the body of the mother and fetus are in conditions of oxygen starvation, and the pregnant woman immediately feels the characteristic symptoms:

  • fast fatiguability;
  • general weakness;
  • headache;
  • shortness of breath, rapid pulse.

A decrease of Ht below the 30% level threatens the normal development of the fetus and requires immediate therapy.


Elevated hematocrit

The increase in Ht is due to a decrease in the amount of fluid in the blood and an increase in its viscosity. Dehydration in a pregnant woman can result from vomiting due to late toxicosis, diarrhea, excessive sweating, insufficient fluid intake.

High hematocrit in pregnant women can also cause hypoxia of the fetus, since with a viscous consistency of blood microcirculation is disturbed.

Normalization of Ht in pregnancy

If the hematocrit is elevated or underestimated, additional tests are performed to establish the cause.


If the level is significantly increased, an abundant drink is recommended, a restriction of salt intake.


If the hematocrit during pregnancy is below normal, and iron deficiency anemia has developed, iron preparations, folic acid are prescribed. Usually the drug is selected individually, since in every organism the iron compounds are assimilated in different ways. In addition to drug treatment, special attention is paid to optimizing the diet and the inclusion of products rich in iron, vitamins. You can increase the number of red blood cells by consuming red meat, beef liver, nuts, fresh fruits and herbs.

It is recommended to review the regime of the day, increase the duration of sleep and the time spent in the open air, and avoid stressful situations.

The composition of the blood can be learned from the video:

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