**Core Concept**
Pregnancy gingivitis is a condition that affects pregnant women, characterized by inflammation of the gums and increased susceptibility to periodontal disease. The condition is often linked to hormonal changes during pregnancy, which can affect the immune system and increase the risk of periodontal disease.

**Why the Correct Answer is Right**
Loesche WJ and co-workers initially demonstrated the association between pregnancy gingivitis and periodontal pathogens. However, Kornman KS further established that P. intermedia is a significant contributor to pregnancy gingivitis. Both researchers played crucial roles in understanding the etiology of this condition.

**Why Each Wrong Option is Incorrect**
**Option A:** Loesche WJ did describe an association between pregnancy gingivitis and periodontal pathogens, but he was not the sole researcher to describe P. intermedia's role.
**Option B:** Kornman KS also contributed significantly to the understanding of pregnancy gingivitis, but he did not act alone in describing P. intermedia's involvement.
**Option D:** This option is incorrect because both Loesche and Kornman made important contributions to understanding the role of P. intermedia in pregnancy gingivitis.

**Clinical Pearl / High-Yield Fact**
Pregnancy gingivitis is a preventable condition that can be managed through good oral hygiene practices, such as regular brushing and flossing, as well as regular dental check-ups during pregnancy.

**✓ Correct Answer: C. Both**