Obstetrics and Gynecology - A.M. Gromova 2000

Changes in the Woman's Body During Pregnancy
Respiratory Function During Pregnancy

Oxygen consumption by the pregnant woman's body increases by more than 30–40% towards the end of gestation. This is supported by changes in cardiac function (myocardial hyperdynamic state), the hematological system (erythrocytosis), and, primarily, by the reorganization of the Respiratory system.

Despite the Lungs being displaced upward due to the elevation of the Diaphragm by the gravid Uterus, the woman's respiratory system operates under hyperventilation conditions during Pregnancy. This is attributed to the following changes.

First, As a result of chest expansion, diaphragmatic excursion increases by several centimeters, which ultimately leads to an increase in tidal volume.

Second, the respiratory rate increases; although breathing becomes shallower due to a reduced residual lung capacity caused by diaphragmatic compression, the incoming oxygen is diluted in a smaller volume of alveolar air, thereby improving gas exchange conditions.

Hyperventilation contributes to a decrease in arterial Pco2, which, against the Background of enhanced renal bicarbonate excretion, establishes a state of compensated alkalosis in the body. This enables the fetus to eliminate H ions across the placental barrier into the maternal Blood.



Last update: 08/08/2026

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