Which of the following are normal respiratory changes in pregnancy? Select all that apply.
Increased tidal volume
Decreased minute ventilation
Increased oxygen consumption
Reduced functional residual capacity
Decreased respiratory rate
Correct Answer : A,C,D
Respiratory changes in pregnancy are driven by hormonal and mechanical factors to meet higher oxygen demand. Progesterone increases respiratory center sensitivity to CO₂, raising tidal volume by about 30–40%. Minute ventilation rises by 30–50%, leading to mild respiratory alkalosis with PaCO₂ 28–32 mmHg (normal non-pregnant PaCO₂ 35–45 mmHg). Oxygen consumption increases by 15–20% due to fetal and maternal metabolic needs. The enlarging uterus elevates the diaphragm, reducing functional residual capacity by 20%. Respiratory rate remains unchanged or slightly increased, not decreased.
Rationale for correct answers
1. Tidal volume increases by 30–40% from progesterone stimulation of the respiratory center. This enhances alveolar ventilation and maintains maternal-fetal gas exchange.
3. Oxygen consumption increases 15–20% to meet maternal and fetal metabolic demands. This adaptation ensures sufficient oxygen delivery across the placenta.
4. Functional residual capacity decreases by about 20% due to diaphragm elevation from the gravid uterus. This lowers lung reserve volume and contributes to dyspnea in late pregnancy.
Rationale for incorrect answers
2. Minute ventilation does not decrease. Instead, it increases by 30–50% because of higher tidal volume. A decrease would cause hypercapnia and impair placental gas exchange.
5. Respiratory rate does not decrease. It usually remains stable or slightly increases by 1–2 breaths/min. A decrease would reduce alveolar ventilation and worsen hypoxemia risk.
Take home points
• Pregnancy increases tidal volume and minute ventilation, not respiratory rate.
• Oxygen consumption rises by 15–20% to support maternal-fetal metabolism.
• Functional residual capacity decreases due to diaphragm elevation.
• Maternal PaCO₂ is reduced to 28–32 mmHg, causing mild compensated respiratory alkalosis.
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Related Questions
Correct Answer is B
Explanation
Estrogenis a steroid hormonethat rises significantly in pregnancy, produced mainly by the placentaafter the first trimester. It influences neurotransmitter regulation, particularly serotonin and dopamine, which are involved in mood control. Rapidly increasing estrogen levels contribute to mood swings, irritability, and emotional lability often reported during pregnancy. Normal estradiol levels increase from ~50–350 pg/mL (follicular phase) to >10,000–40,000 pg/mL in late pregnancy.
Rationale for correct answer
2.Estrogen fluctuations and high levels alter central nervous system neurotransmission, especially serotonin, leading to emotional instability and mood swings. This is the primary hormonal factor for psychological changes during pregnancy.
Rationale for incorrect answers
1.Human placental lactogen regulates maternal glucose metabolism and increases insulin resistance to ensure fetal glucose supply. It does not act directly on neurotransmitters or cause mood swings.
3.Insulin regulates blood glucose by facilitating cellular glucose uptake. While hypoglycemia or hyperglycemia can cause irritability, insulin itself is not the hormonal cause of mood swings in pregnancy.
4.Thyroxine (T4) regulates metabolism and oxygen consumption. Abnormal thyroid hormone levels can cause anxiety or depression, but normal pregnancy mood swings are not primarily due to thyroxine.
Take home points
• Estrogen is the main hormone responsible for mood swings in pregnancy.
• High estrogen levels affect serotonin and dopamine pathways in the brain.
• Human placental lactogen and insulin regulate glucose, not emotions.
• Thyroxine regulates metabolism; abnormal levels may mimic mood changes but are not typical causes.
Correct Answer is C
Explanation
Goodell’s signis the softening of the cervical tipobserved around 6–8 weeks of pregnancy. It is caused by increased vascularity, hyperplasia, and hypertrophyof cervical glands due to estrogen and progesterone. Normal cervical tissue is firm, but with increased blood flow and edema, the cervix becomes softand pliable.
Rationale for correct answer
3.Goodell’s sign results from increased vascularity leading to engorgement, along with hyperplasia and hypertrophy of cervical glands. Estrogen increases blood flow and stimulates cervical tissue changes, causing the softening of the cervix detected on pelvic exam.
Rationale for incorrect answers
1.Decreased vascularity would make the cervix less perfused and firmer, not softer. Goodell’s sign specifically results from increased blood flow, not reduction.
2.Increased collagen content makes tissue more rigid and firm. In pregnancy, cervical collagen is remodeled and partially degraded, contributing to softening, not increased firmness.
4.Uterine contractions do not cause early cervical softening. Contractions influence cervical effacement and dilation during labor, but Goodell’s sign occurs in early pregnancy before labor begins.
Take home points
• Goodell’s sign is cervical softening detected at 6–8 weeks of pregnancy.
• It results from increased vascularity, hyperplasia, and hypertrophy of cervical glands.
• Increased collagen would firm the cervix, but in pregnancy collagen is remodeled for softness.
• Uterine contractions affect dilation in labor, not early pregnancy softening.
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