Physiological Changes in Cardiovascular and Respiratory System during Pregnancy

Subject: Midwifery I (Theory)

Overview

The physiological change in the cardiovascular system is an increase in heart size due to increased workload. Because of the pressure from the growing fetus, it may also be exhibited upward and to the left, rotating anteriorly. Blood pressure remains within normal ranges, with a minor drop of about 100 mmHg throughout the mid-trimester, followed by a steady recovery to normal at term. Increased venous pressure in the lower limbs during pregnancy can result in varicose veins, hemorrhoids, and dependent edema of the feet. Iron absorption doubles throughout pregnancy to satisfy the demands of increased maternal blood volumes, tissue mass, and fetal needs. Because 1000 mg of iron is required during pregnancy, iron supplementation is advised.

Changes in the Cardiovascular System

The workload increased the size of the heart. Because of the pressure from the expanding fetus, it may also be presented upward and to the left turning anteriorly.
During pregnancy, the total quantity of circulating blood volume increases by 30% to 40% (1000ml).
The volume of red blood cells increases by 200 mL. (5-10 percent ). Total hemoglobin increases by 90gm (20%), whereas red cell (up to 4ml/cumm), hemoglobin (up to 11gm%), and hematocrit values decrease in peripheral blood due to haemodilution.
Because of the increased fibrinogen concentration, ESR rises to 40-50 mm (first hour).
Due to increased intake, platelet count shows a little decline. Clotting factors (VII, VIII, IX, X) increase. Plasma antithrombin III levels and fibrinolytic activity fall.
In the latter stages of pregnancy, aortocaval compression by the gravid uterus might interfere with the venous return to the heart, resulting in hypertension. This impact is most noticeable when lying supine. Supine hypertension can be immediately alleviated by changing positions. Supine hypertension can be immediately treated by shifting the mother's position from supine to left lateral recumbent.
Blood pressure remains within normal ranges, but drops by roughly 100 mmHg throughout the third trimester, followed by a gradual return to normal at term.
Increased venous pressure in the lower limbs produced by prolonged standing or sitting during pregnancy can result in varicose veins, hemorrhoids, and dependent edema of the feet.
The control venous pressure increased by 5-10 mmH20.
From the 20th week of pregnancy, plasma volume increases. Because of haemodilution, physiological anemia is also common during pregnancy. Mild edema is caused by a reduction in plasma protein.
To satisfy the demands of rising maternal blood volumes, tissue mass, and fetal needs, iron absorption doubles during pregnancy. Approximately 1000 mg of iron is necessary during pregnancy, hence iron supplementation is advised.
White blood cell counts typically rise from 9000/cumm to around 12,000/cumm, with a further rise to 15,000/cumm during labor. In the postpartum phase, a moderate level of leukocytosis of 15000-18000/cumm is usual.

Changes in the Respiratory Period

The upper respiratory tract is prone to hyperemia and congestion, which makes phlegm, sinusitis, and epistaxis more likely.
The inspiratory rate has increased somewhat. The 'tidal volume' and 'minute ventilation' both rise by 30-40%. The 'functional reserve capacity and 'inspiratory reserve volume' could be reduced by 20%.
Changes in blood gasses are common; PO2 rises to 100 mmHg, whereas PCO2 falls to 27-38 mmHg. With increased renal bicarbonate excretion, the pH remains normal.
Dyspnea is a frequent symptom of pregnancy, affecting 60-70 percent of women to varying degrees.
The impact of progesterone on the respiratory center is most likely responsible for maternal hyperventilation. It is seen as a protective precaution to avoid exposing the fetus to high amounts of CO2.

Note:

Increased inspiration > increased oxygen intake > high arterial PO2 (105 mmHg from 95 mmHg)> increased expiration > more CO2 expired > low pressure of CO2 mother’s blood> easy transfer of CO2 from the fetus mother’s blood. Respiratory rate rises from 15 to 18 breaths per min.

References

Kovacs CS. Calcium metabolism during pregnancy and lactation. NCBI Bookshelf. http://www.ncbi.nlm.nih.gov/books/NBK279173/
HealthLine. 2005. 2017 http://www.healthline.com/health/pregnancy/bodily-changes-during
BC Open Textbook. https://opentextbc.ca/anatomyandphysiology/chapter/28-4-maternal-changes-during-pregnancy-labor-and-birth/
Hadassah Medical Center. http://www.hadassah-med.com/giving-birth/hadassah-birthing-club/throughout-pregnancy/physiological-changes-during-pregnancy
Tuitui R. 2002, A textbook of Midwifery A (Antenatal), 3rd edition, Vidyarthi Pustak Bhandari (Publisher and Distributor), Bhotahity, Kathmandu
Tuitui R. 2002, A textbook of Midwifery B (Intranatal), 3rd edition, Vidyarthi Pustak Bhandari (Publisher and Distributor), Bhotahity, Kathmandu

Things to remember

The physiological change in the cardiovascular system is an increase in heart size as a result of increasing workload.
Because of the pressure from the expanding fetus, it may also be presented upward and to the left turning anteriorly.
During pregnancy, the total quantity of circulating blood volume increases by 30% to 40% (1000ml).
Blood pressure remains within normal ranges, but drops by roughly 100 mmHg throughout the third trimester, followed by a gradual return to normal at term.
Increased venous pressure in the lower limbs produced by prolonged standing or sitting during pregnancy can result in varicose veins, hemorrhoids, and dependent edema of the feet.
To satisfy the demands of rising maternal blood volumes, tissue mass, and fetal needs, iron absorption doubles during pregnancy. Approximately 1000 mg of iron is necessary during pregnancy, hence iron supplementation is advised.
The upper respiratory tract is prone to hyperemia and congestion, leading to phlegm, sinusitis, and epistaxis as the respiratory system changes.
Dyspnea is a frequent symptom of pregnancy, affecting 60-70 percent of women to varying degrees.
The impact of progesterone on the respiratory center is most likely responsible for maternal hyperventilation. It is seen as a protective precaution to avoid exposing the fetus to high amounts of CO2.

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Maternal changes in pregnancy

Questions and Answers

What are the physiological changes that occur in respiratory system during pregnancy ?

Phlegm, sinusitis, and epistaxis are all more likely to develop in an upper respiratory tract that is prone to hyperemia and congestion.
The inspiratory rate has somewhat increased. "Minute ventilation" and "tidal volume" both rise by 30–40%. There may be a 20% reduction in both the "functional reserve capacity" and the "inspiratory reserve volume."
Commonly seen blood gas changes include an increase in PO2 above 100 mmHg and a decrease in PCO2 to between 27 and 38 mmHg. With increased renal bicarbonate excretion, the pH remains normal.
Sixty to seventy percent of pregnant women experience dyspnea to varied degrees.
The respiratory center-active effects of progesterone on mothers are likely to be to blame for their hyperventilation. Preventing the fetus from being exposed to too much CO2 is viewed as a protective measure.

Explain the physiological changes in the cardiovascular system ?

Due to an increase in workload, heart size rose. Due to pressure from the developing fetus, it may also be seen as turning anteriorly, upward, and to the left.
During pregnancy, the total volume of blood in circulation rises by 30% to 40% (or 1000ml).
The volume of red blood cells grows by 200 ml (5–10%). Due to haemodilution, total hemoglobin increased by 90gm (20%), red cell concentration decreased by up to 4ml/cumm, and hemoglobin levels increased by up to 11gm (10%).
Due to an increase in fibrinogen content, ESR rises to 40–50 mm within the first hour.
Increased intake causes a small drop in platelet count. Clotting variables (variables VII, VIII, IX, and X) increase. Plasma fibrinolytic activity and antithrombin III levels drop.
In the latter stages of pregnancy, aortocaval compression by the gravid uterus can prevent the heart's venous return and result in hypertension. The supine position brings out this impact the most. Changing the supine position can quickly reduce supine hypertension. The supine maternal position can be swiftly changed to the left lateral recumbent posture to reduce supine hypertension.
Despite a little drop of roughly 100 mmHg in the middle of the third trimester, blood pressure remains within acceptable ranges and gradually returns to normal at term. Varicose veins, hemorrhoids, and dependent edema of the feet can develop during pregnancy as a result of increased venous pressure in the lower limbs brought on by extended standing or sitting.
The control venous pressure showed a 5–10 mmH20 increase.
Plasma volume starts to rise about week 20 of pregnancy. Due to haemodilution, physiological anemia is also typical during pregnancy. Mild enema is caused by a drop in plasma protein.
To satisfy the demands of expanding maternal blood volumes, tissue mass, and fetal needs, iron absorption doubles during pregnancy. Since pregnant women need roughly 1000 mg of iron, iron supplementation is advised.
The white blood cell counts grow normally from 9000/cumm to 12,000/cumm and then rise to 15,000/cumm during labor. In the postpartum period, a moderate leukocytosis of 15000–18000/cumm is frequently seen.