By the time of childbirth, maternal blood volume typically exceeds its preconception volume by approximately what percentage?

1. Pregnancy places substantially increased demands on the maternal circulatory system. 2. Blood volume must rise to manage fetal nourishment and waste removal. 3. This increase reaches 30 percent above preconception volume by childbirth. 4. 5 percent and 15 percent are both different figures a reader might guess from memory, but neither matches the specific figure given here. 5. 60 percent is also incorrect for the same reason: it does not match the specific figure given here. 6. That corresponds to approximately 1 to 2 additional liters of blood. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 28 "Development and Inheritance", p.1344 §Changes in Organ Systems During Pregnancy_