**Core Concept**
The definitive signs of pregnancy are a set of clinical indicators that confirm pregnancy beyond a doubt. These signs are crucial in obstetrics and gynecology for confirming pregnancy, assessing fetal development, and guiding prenatal care.

**Why the Correct Answer is Right**
The definitive signs of pregnancy include fetal heart sounds, quickening (feeling the baby move), fetal movements, and fetal parts palpable on abdominal examination. However, the option that is not a definitive sign of pregnancy is the one that does not directly relate to fetal presence or development.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a definitive sign of pregnancy. Definitive signs involve direct evidence of fetal presence or development, whereas this option might be related to non-specific symptoms or indirect indicators.
**Option B:** This option is also not a definitive sign of pregnancy. While it may be related to pregnancy, it is not a direct indicator of fetal presence or development.
**Option C:** This option is not a definitive sign of pregnancy. Definitive signs of pregnancy are typically related to direct evidence of fetal presence or development, whereas this option might be related to non-specific symptoms or indirect indicators.

**Clinical Pearl / High-Yield Fact**
One key point to remember is that the definitive signs of pregnancy are crucial in confirming pregnancy and guiding prenatal care. Fetal heart sounds are often the first definitive sign of pregnancy, detectable as early as 5-6 weeks of gestation.

**Correct Answer: D.**