Final answer:
The correct understanding of common pregnancy discomforts around 20 weeks of gestation is expecting some back pain due to the increased size and weight of the growing fetus.
Step-by-step explanation:
The statement that indicates an understanding of the common discomforts associated with pregnancy at 20 weeks gestation is: "I should expect to experience some back pain as my pregnancy progresses." This understanding is accurate since the growing fetus increases in size, leading to an altered center of gravity and extra strain on the back muscles. In addition, gastrointestinal issues such as gastric reflux or heartburn are common due to the increase in upward pressure from the growing uterus on the stomach. A healthy balance of physical activity and diet, rather than strict avoidance or stringent diets, is recommended to manage these discomforts.