Which sign of pregnancy is recognized for its reliance on ultrasound?

• A. Hegar's sign
• B. Positive pregnancy test
• C. Fetal heart sounds
• D. Chadwick's sign

Answer: (C)

The sign of pregnancy that is recognized for its reliance on ultrasound is the detection of fetal heart sounds. This sign typically manifests around six weeks of gestation and can be confirmed through the use of ultrasound technology. Fetal heart sounds indicate that a fetus is developing and usually can be visualized as early as the sixth week but is more commonly assessed a bit later in the first trimester.

Ultrasound provides a clear, visual confirmation of fetal heart activity, which is a significant indicator of a viable pregnancy. In contrast, other signs, such as Hegar's sign, Chadwick's sign, and positive pregnancy tests, do not specifically require ultrasound for confirmation. Hegar's sign refers to the softening of the lower uterine segment as felt during a physical examination, Chadwick's sign relates to the bluish coloration of the cervix and vagina, and a positive pregnancy test measures hormone levels in the urine or blood. While these signs can indicate a pregnancy, they do not rely on imaging technology to be confirmed.

Thus, the identification of fetal heart sounds through ultrasound is a definitive measure of pregnancy that is scientifically validated and widely accepted in clinical practice.