Cody has always carefully controlled her caloric intake, and is lean. During her unplanned pregnancy, she continued to eat the same, hoping that taking prenatal vitamins and minerals would ensure that her fetus would grow normally. Her only complication during pregnancy was persistent constipation and consequent hemorrhoids. She gained only the minimum weight suggested by her doctor, and

Question

delivered a healthy, full-term infant; her pre-pregnancy weight was rapidly reestablished. Propose an explanation for how she managed to gain enough weight, did not violate the law of conservation of mass, and for her only complication. What does this suggest about "eating for two" that some pregnant women do?

What will be an ideal response?

Answer 1

She must have inefficiently absorbed calories prior to her pregnancy, losing many potential calories in her feces. When she became pregnant, one of her physiological changes included an increase in nutrient (and thus calorie) absorption. This would also contribute to her constipation, as her feces retained less water than normal and thus were more difficult to eliminate. It is not possible for her to have gained more weight than she ate; no one can violate the law of conservation of mass. Most obstetricians recommend only a slight increase in calories during pregnancy for this reason, and women who indulge in overeating too often are likely to gain unnecessary body fat and may produce a fetus that is larger than it should be.