What is the expected increase in maternal blood volume during pregnancy?
10–20%
30–50%
60–80%
90–100%
The Correct Answer is B
Maternal blood volume increase in pregnancy occurs to meet increased metabolic demands, uteroplacental circulation, and fetal development. Plasma volume rises by 40–50% and red blood cell mass rises by 20–30%. This results in hemodilution called physiologic anemia. Normal hematocrit in pregnancy is 32–42%, hemoglobin 11–12 g/dL, and normal non-pregnant hematocrit is 36–46%. Increased cardiac output and reduced systemic vascular resistance maintain adequate perfusion.
Rationale for correct answer
2. Maternal blood volume increases by 30–50% during pregnancy. This expansion supports uteroplacental perfusion and compensates for blood loss at delivery. The stem asked for the expected increase, which directly aligns with this physiologic range.
Rationale for incorrect answers
1. A 10–20% increase is too low and would not meet pregnancy demands. Such a small increase could not sustain placental blood flow or provide reserve for intrapartum hemorrhage. Scientific data consistently report expansion closer to 40–50%.
3. A 60–80% increase would be excessive and pathologic. This degree of hypervolemia would lead to severe hemodilution, pulmonary edema, and possible high-output cardiac failure. Physiologically, maternal cardiovascular adaptation plateaus at about 50%.
4. A 90–100% increase is not physiologically possible. Doubling blood volume would cause circulatory overload and profound cardiopulmonary compromise. Such levels are not compatible with normal adaptation in pregnancy.
Take home points
• Maternal blood volume increases by 30–50% during pregnancy.
• Hemodilution results in physiologic anemia with hemoglobin 11–12 g/dL and hematocrit 32–42%.
• Increased plasma volume supports uteroplacental circulation and compensates for delivery blood loss.
• Differentiation is important from pathologic hypervolemia such as preeclampsia or heart failure.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is ["A","C","E"]
Explanation
Constipation in pregnancyis common due to hormonal and mechanical factors. Progesteronerelaxes smooth muscle, slowing colonic transit, while the enlarging uterus compresses the intestines. Normal bowel movement frequency ranges from 3 times/day to 3 times/week. Low fiberintake (<25 g/day), reduced activity, and inadequate hydrationworsen symptoms. Typical clinical features are infrequent stools, straining, and hard stool consistency. Preventive strategies include dietary fiber >25–30 g/day, fluid intake >2 L/day, regular exercise, and meal pattern adjustment.
Rationale for correct answers
1.Increased fiber intake enhances stool bulk and water retention, stimulating peristalsis. Daily intake of 25–30 g is recommended for pregnant women to prevent constipation.
3.Regular exercise improves bowel motility by stimulating colonic activity. Activities like walking 30 minutes daily are safe and effective in pregnancy.
5.Promoting small, frequent meals helps regulate digestion, prevents gastric overfilling, and maintains steady bowel function. This supports peristalsis and reduces bloating.
Rationale for incorrect answers
2.Reducing fluid intake worsens constipation. Adequate hydration (≥2 L/day) softens stools and supports normal bowel function. Low fluid intake results in harder stools and straining.
4.Avoiding stool softeners is incorrect. Stool softeners such as docusate sodium are considered safe in pregnancy and may be used when lifestyle measures are insufficient. They reduce straining without systemic absorption.
Take home points
• Progesterone-induced smooth muscle relaxation slows bowel transit in pregnancy.
• Adequate fiber, fluids, and exercise are first-line preventive strategies.
• Small frequent meals regulate digestion and reduce bloating.
• Stool softeners are safe in pregnancy if lifestyle changes are inadequate.
Correct Answer is C
Explanation
Relaxinis a peptide hormonesecreted mainly by the corpus luteum, decidua, and placenta during pregnancy. It increases collagen remodelingand connective tissue elasticity, promoting relaxation of pelvic ligaments and increased joint mobility to facilitate childbirth. Relaxin levels peak in the first trimester and again near term. Normal effects also include softening of the cervix and inhibition of uterine contractions to maintain early pregnancy.
Rationale for correct answer
3.Relaxin causes relaxation and softening of pelvic ligaments and joints, especially the pubic symphysis and sacroiliac joints. This increases pelvic mobility and prepares the birth canal for labor. It also contributes to cervical ripening through collagen breakdown and connective tissue remodeling.
Rationale for incorrect answers
1.Oxytocin stimulates uterine smooth muscle contractions during labor and milk ejection from the breast. It does not influence ligament relaxation or pelvic joint mobility.
2.Prolactin is primarily involved in mammary gland development and initiation of lactation. It has no role in pelvic ligament relaxation or connective tissue changes in pregnancy.
4.Cortisol regulates metabolism and has a role in fetal lung maturation, but it does not act on pelvic ligaments or joints. Its effects are primarily catabolic and immunomodulatory, not structural relaxation.
Take home points
• Relaxin softens pelvic ligaments and joints to facilitate delivery.
• It is secreted by the corpus luteum, decidua, and placenta.
• Cervical ripening and inhibition of uterine contractions are additional effects.
• Oxytocin, prolactin, and cortisol have different physiological roles unrelated to ligament relaxation.
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