A 28-year-old woman, gravida 3 para 2, at 31 weeks gestation comes to the office for a prenatal visit. The patient has had increasing shortness of breath while climbing stairs and during long walks for the past few weeks but has had no cough, sick contacts, hemoptysis, orthopnea, or chest pain. She has had no contractions or vaginal bleeding, and fetal movement is normal. The patient has no chronic medical conditions, and her pregnancy has been uncomplicated. Blood pressure is 110/80 mm Hg, pulse is 70/min, and respirations are 18/min. Fetal heart tones are normal. Cardiac examination reveals no rubs or murmurs. The lungs are clear to auscultation bilaterally. The remainder of the examination is unremarkable. Which of the following laboratory findings will most likely be found in this patient?

Question

A 28-year-old woman, gravida 3 para 2, at 31 weeks gestation comes to the office for a prenatal visit.  The patient has had increasing shortness of breath while climbing stairs and during long walks for the past few weeks but has had no cough, sick contacts, hemoptysis, orthopnea, or chest pain.  She has had no contractions or vaginal bleeding, and fetal movement is normal.  The patient has no chronic medical conditions, and her pregnancy has been uncomplicated.  Blood pressure is 110/80 mm Hg, pulse is 70/min, and respirations are 18/min.  Fetal heart tones are normal.  Cardiac examination reveals no rubs or murmurs.  The lungs are clear to auscultation bilaterally.  The remainder of the examination is unremarkable.  Which of the following laboratory findings will most likely be found in this patient?

Quizplus · Accepted Answer

Eductional Objective: The normal physiology of pregnancy involves chronic hyperventilation caused by elevated progesterone levels stimulating an increase in central respiratory drive.  This creates an expected respiratory alkalosis with metabolic compensation (increased renal bicarbonate excretion) that helps facilitate the transport of acidic wastes from, and the transport of oxygen to, the developing fetus.

A 28-Year-Old Woman, Gravida 3 Para 2, at 31 Weeks