NLS Q19: Cord blood pH measurements can be made from umbilical cords, when these have been immediately double-clamped, up to 60 min after delivery. Select one: a. True b. False Incorrect Feedback Studies have shown that blood pH remains relatively stable in a double-clamped umbilical cord for up to 60 min. In contrast, values for blood lactate and base excess deteriorate much more quickly and are unreliable after 20 min. Blood pH from an unclamped cord is also unreliable after 20 min.