**Core Concept**
Uterine atony is a condition where the uterus fails to contract after childbirth, leading to excessive bleeding. The definition of postpartum hemorrhage (PPH) is crucial in this context, as it guides the management and classification of the condition.

**Why the Correct Answer is Right**
Postpartum hemorrhage is defined as a blood loss of more than 500 mL after vaginal delivery or more than 1000 mL after cesarean delivery. This definition is based on the World Health Organization's (WHO) guidelines for managing postpartum hemorrhage. Uterine atony is a leading cause of PPH, and prompt recognition and treatment are essential to prevent maternal morbidity and mortality.

**Why Each Wrong Option is Incorrect**
**Option A:**
* This option is incorrect because 200 mL is considered a normal blood loss after vaginal delivery, and it does not meet the criteria for postpartum hemorrhage.

**Option B:**
* This option is incorrect because 300 mL is still considered a moderate blood loss, but it does not meet the criteria for postpartum hemorrhage.

**Option C:**
* This option is incorrect because 700 mL is significantly more than the threshold for postpartum hemorrhage, but it is still below the threshold for the more severe classification.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that postpartum hemorrhage can be classified into four degrees: 1st degree (500-999 mL), 2nd degree (1000-1499 mL), 3rd degree (1500-1999 mL), and 4th degree (2000 mL or more). Accurate classification guides the management and treatment of PPH.

**Correct Answer: C. 1000 mL.**