Which is considered a presumptive sign of pregnancy?

Amenorrhea, or the absence of menstruation, is considered a presumptive sign of pregnancy because it is one of the earliest indicators that a woman might be pregnant. This sign is based on the changes in hormonal levels that occur when a conception takes place. During pregnancy, elevated levels of hormones such as human chorionic gonadotropin (hCG) prevent the normal menstrual cycle from occurring, which is why a missed period often prompts a woman to take a pregnancy test.

In contrast, the other options represent signs that are either more definitive or related to pregnancy but not classified as presumptive. Ballottement refers to a physical examination technique that typically occurs later in pregnancy, while cervical dilation is a sign associated with labor. Increased systemic circulation is related to the physiological changes that happen during pregnancy but does not serve as an early indicator. Thus, amenorrhea stands out as the most direct and early sign of pregnancy, making it the correct choice.