**Core Concept**
Bacterial vaginosis (BV) is a type of vaginal infection caused by an imbalance of the normal vaginal microbiota, leading to an overgrowth of various bacteria. This condition is characterized by a loss of the protective lactobacilli and an increase in anaerobic bacteria such as Gardnerella vaginalis.

**Why the Correct Answer is Right**
The correct answer will be the characteristic that is NOT typical of bacterial vaginosis. BV is often associated with an increased vaginal pH, which is usually elevated above 4.5. This is due to the overgrowth of anaerobic bacteria, which do not produce lactic acid, thereby disrupting the normal acidic environment of the vagina. The presence of clue cells, which are vaginal epithelial cells coated with bacteria, is another hallmark of BV.

**Why Each Wrong Option is Incorrect**
**Option A:** A fishy odor is a characteristic feature of bacterial vaginosis, which is often described as a strong, unpleasant smell that may be more noticeable after sexual intercourse or during menstruation. This is due to the production of amines by the anaerobic bacteria.

**Option C:** A thin, white or gray discharge is a common symptom of bacterial vaginosis, which may be more noticeable after sexual intercourse or during menstruation.

**Clinical Pearl / High-Yield Fact**
It's essential to note that bacterial vaginosis is not caused by a single pathogen but rather by an imbalance of the normal vaginal microbiota. This makes it challenging to diagnose using traditional microbiological methods, and diagnosis often relies on clinical symptoms and the presence of clue cells.

**Correct Answer: D.**