Which of the following is a probable sign of pregnancy?

Uterine enlargement is a probable sign of pregnancy because it indicates that the uterus is growing to accommodate a developing fetus. This physical change occurs as early as the first trimester and becomes more noticeable as pregnancy progresses. As the uterus expands, it displaces other organs and can often be palpated during a physical examination.

While amenorrhea, fatigue, and nausea are also associated with pregnancy, they can have other causes and are considered more subjective symptoms rather than definitive signs. Amenorrhea, or the absence of menstruation, can occur due to various factors such as hormonal imbalances, stress, or changes in lifestyle. Fatigue is a common symptom in many conditions, not just pregnancy, often connected to lifestyle, illness, or sleep disorders. Nausea can also be related to various gastrointestinal issues, stress, or infections. In contrast, uterine enlargement is a clear physiological change that strongly indicates pregnancy.