In pregnancy, the arterial pH is typically in which range?

• A. 7.42 to 7.45
• B. 7.50 to 7.55
• C. 7.30 to 7.35
• D. 7.38 to 7.40

Answer: (A)

In pregnancy there is a mild respiratory alkalosis from increased ventilation due to hormonal changes, especially progesterone. This pushes the arterial pH toward the upper end of the normal range, so it’s typically around 7.42 to 7.45. The normal arterial pH is about 7.35 to 7.45, but pregnancy tends to sit closer to the high end. The kidneys compensate by lowering bicarbonate, but the pH remains near the upper normal value. Choices that show more alkalemia (7.50–7.55) or acidity (7.30–7.35) or a mid-normal range (7.38–7.40) don’t fit as well as the upper end of normal seen in pregnancy.