North American Registry of Midwives (NARM) Practice Exam

What factors can cause a woman's hemoglobin levels to have a higher lower limit of normal?

1. Living at sea level

2. Increased red cell mass due to high altitude

3. Being physically inactive

4. Having low blood pressure

The correct answer is: Increased red cell mass due to high altitude

The correct answer is based on the physiological adaptation that occurs with altitude. At higher altitudes, the atmospheric pressure decreases, which can lead to a lower availability of oxygen in the environment. To compensate for this reduced oxygen availability, the body responds by increasing the production of red blood cells, a process primarily regulated by erythropoietin. This increase in red blood cells leads to a higher red cell mass and subsequently elevates hemoglobin levels. Consequently, women living at high altitudes will often have a higher lower limit of normal for hemoglobin levels as their bodies adapt to ensure efficient oxygen transport despite the lower oxygen concentrations in the air. This adaptive mechanism is crucial for maintaining proper physiological function in environments where oxygen is limited. Other factors mentioned, such as living at sea level, being physically inactive, and having low blood pressure, do not facilitate an increase in hemoglobin levels. Living at sea level would typically result in average hemoglobin levels without the adaptive increase seen at high altitudes. Physical inactivity generally does not stimulate increased red cell production, and low blood pressure is not directly related to hemoglobin levels but rather reflects cardiovascular status and volume status in the body. Thus, these options do not contribute to a higher lower limit of normal for