Which of the following are common physiological changes affecting the cardiovascular system during pregnancy? Select all that apply.
Increased blood volume
Decreased cardiac output
Physiological anemia (dilutional)
Increased systemic vascular resistance
Hypercoagulable state
Correct Answer : A,E
Cardiovascular changes in pregnancy are adaptive responses that maintain maternal and fetal perfusion. Blood volume rises by 30–50% and cardiac output increases by 30–50% due to higher stroke volume and heart rate. Systemic vascular resistance decreases from progesterone-mediated vasodilation. Physiological anemia results from disproportionate plasma expansion. The maternal state becomes hypercoagulable to prevent postpartum hemorrhage, with increased clotting factors VII, VIII, IX, X, and fibrinogen.
Rationale for correct answers
1. Blood volume increases 30–50% to sustain uteroplacental circulation and provide a reserve for delivery blood loss. This is a normal physiologic change.
3. Physiological anemia occurs because plasma volume rises more than red cell mass. Hematocrit falls to 32–42% and hemoglobin to 11–12 g/dL, producing dilutional anemia.
5. Pregnancy is a hypercoagulable state due to increased coagulation factors and fibrinogen, which lowers fibrinolytic activity. This adaptation reduces postpartum hemorrhage risk but raises thromboembolism risk.
Rationale for incorrect answers
2. Cardiac output does not decrease. Instead, it rises by 30–50% from increased heart rate and stroke volume, peaking in mid-pregnancy. A decrease would compromise placental perfusion.
4. Systemic vascular resistance does not increase. Progesterone and prostaglandins cause vasodilation, lowering resistance to accommodate higher blood volume without severe hypertension. An increase would predispose to preeclampsia.
Take home points
• Blood volume and cardiac output increase significantly in pregnancy.
• Physiologic anemia develops due to disproportionate plasma expansion.
• Pregnancy induces a hypercoagulable state to prevent hemorrhage but raises clotting risk.
• Systemic vascular resistance decreases, distinguishing normal adaptation from hypertensive disorders.
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Related Questions
Correct Answer is B
Explanation
Supine hypotensive syndromeoccurs in late pregnancy when the gravid uteruscompresses the inferior vena cavawhile lying supine, reducing venous returnand decreasing cardiac output. This leads to maternal hypotension, dizziness, pallor, and tachycardia. Normal maternal cardiac output in pregnancy increases by 30–50% (from 4.5 L/min to 6–7 L/min).
Rationale for correct answer
2.Supine hypotensive syndrome results from compression of the inferior vena cava by the enlarged uterus, especially in the third trimester. This reduces venous return, lowers preload, and decreases cardiac output, causing dizziness when lying flat. Symptoms resolve when the woman turns to the left lateral position.
Rationale for incorrect answers
1.Increased cardiac output occurs in pregnancy due to increased blood volume and stroke volume, peaking at 30–50% above baseline. This increase improves tissue perfusion and does not cause dizziness when supine. Instead, reduced output from vena cava compression explains the symptom.
3.Physiological anemia in pregnancy results from plasma volume expansion exceeding red cell mass increase, leading to lower hematocrit values (normal pregnancy hemoglobin 11–12 g/dL, hematocrit 32–34%). It causes fatigue and pallor, not positional dizziness specific to lying supine.
4.Hyperventilation occurs due to progesterone-mediated respiratory drive increase, leading to mild respiratory alkalosis (PaCO₂ 28–32 mmHg, normal pregnancy pH 7.40–7.45). This causes dyspnea but not dizziness limited to supine position.
Take home points
• Supine hypotensive syndrome results from gravid uterine compression of the inferior vena cava.
• Symptoms include dizziness, pallor, hypotension, and tachycardia when lying flat.
• Turning to the left lateral position relieves symptoms by restoring venous return.
• Physiological anemia and hyperventilation are normal pregnancy changes but do not explain positional dizziness.
Correct Answer is A
Explanation
Heartburn in pregnancyis primarily due to progesterone-induced relaxationof the lower esophageal sphincter, which allows gastric acid refluxinto the esophagus. Progesterone also delays gastric emptying and decreases gastrointestinal motility. Normal lower esophageal sphincter pressure decreases progressively during pregnancy, predisposing to gastroesophageal reflux. Symptoms usually peak in the second and third trimesters.
Rationale for correct answer
1.Heartburn is the burning substernal sensation caused by reflux of gastric acid. Progesterone relaxes the lower esophageal sphincter, allowing backflow of stomach contents. This is the most direct gastrointestinal discomfort linked with progesterone-induced relaxation.
Rationale for incorrect answers
2.Constipation in pregnancy is caused by decreased bowel motility and prolonged transit time due to progesterone’s effect on smooth muscle. However, it is not due to lower esophageal sphincter relaxation but rather intestinal smooth muscle relaxation.
3.Nausea is primarily related to increased human chorionic gonadotropin and estrogen levels, especially in the first trimester. It is not due to esophageal sphincter changes.
4.Gingivitis results from increased vascularity, edema, and hormonal effects on gingival tissue, often leading to bleeding gums. It is unrelated to sphincter relaxation or acid reflux.
Take home points
• Heartburn in pregnancy results from progesterone-induced relaxation of the lower esophageal sphincter.
• Constipation is also progesterone-related but involves reduced intestinal motility, not sphincter relaxation.
• Nausea is linked to elevated hCG and estrogen levels, particularly in early pregnancy.
• Gingivitis arises from vascular and hormonal changes in gingival tissues, not gastrointestinal reflux.
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