These RNC-OB practice questions target physiology — including CO. The complete RNC-OB deck holds 1050 flashcards, 100 of them dedicated to this topic. Study the free samples below, then unlock the whole collection for a one-time $7.
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A patient at 28 weeks gestation has a Hgb of 10.8 g/dL, down from 12.8 g/dL pre-pregnancy. What is the primary physiological mechanism for this change?
Show answer →This is physiologic anemia of pregnancy. It occurs because plasma volume increases by 45-50%, while RBC mass only increases by 20-30%. The disproportionate increase in plasma relative to RBCs leads to hemodilution. NCC Exam Strategy: Recognize that Hgb >11.0 in 1st/3rd trimesters and >10.5 in the 2nd trimester is considered normal. This expansion is vital for placental perfusion and protecting against blood loss during delivery.
When does maternal cardiac output (CO) reach its absolute peak during the entire pregnancy, labor, and postpartum period?
Show answer →The absolute peak occurs in the immediate postpartum period (first 10-15 minutes). CO increases by 60-80% above pre-labor values due to autotransfusion of approximately 500 mL of blood from the involuting uterus and the relief of inferior vena cava compression. Clinical Pearl: This is the highest-risk period for patients with underlying cardiac disease (e.g., CHF or valve stenosis) to experience decompensation or pulmonary edema.
A patient at 22 weeks gestation presents with a BP of 98/58 mmHg (Baseline 118/76). What physiological mechanism explains this nadir in blood pressure?
Show answer →Systemic Vascular Resistance (SVR) decreases by 20-30% during pregnancy, reaching its lowest point (nadir) at 20-24 weeks. This is driven by high levels of progesterone (smooth muscle relaxant), increased nitric oxide, and prostaglandins. NCC Tip: Diastolic BP typically drops more than systolic (10-15 mmHg vs 5-10 mmHg). BP should return to pre-pregnancy baseline levels by term. Failure to return to baseline or an increase may indicate gestational hypertension.
A patient at 38 weeks lies supine for an ultrasound and reports sudden nausea and faintness. Fetal monitoring shows a late deceleration. What is the pathophysiological cause?
Show answer →Supine Hypotensive Syndrome (Aortocaval Compression). The heavy gravid uterus compresses the inferior vena cava when the patient is supine, significantly reducing venous return (preload) to the heart. This can decrease cardiac output by up to 30%, leading to maternal hypotension and reduced uterine blood flow (causing fetal decelerations). Management: Immediate lateral tilt or wedge under the right hip to displace the uterus.
During a physical assessment of a healthy 34-week pregnant patient, which heart sound would be considered an abnormal/pathological finding?
Show answer →An S4 (atrial gallop) is always considered pathological in pregnancy. Normal findings due to hypervolemia and increased flow include: 1. A loud S1 split. 2. An S3 (ventricular gallop) in up to 80% of patients. 3. Grade I or II systolic ejection murmurs. Note: Diastolic murmurs are also considered pathological and require a cardiology referral. NCC often tests the distinction between the normal S3 and abnormal S4 in pregnancy.
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Try 30 free RNC-OB cards firstThe full RNC-OB deck contains 1050 flashcards, and 100 of them focus on physiology. This page shows 5 free samples.
Our RNC-OB deck dedicates 100 of 1050 cards (10%) to physiology — always cross-check the official NCC exam outline for the current blueprint weighting.
Yes — the samples on this page are free, and the RNC-OB preview page has 30 more free cards. Full access to all 1050 cards is a one-time $7.
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