**Core Concept**
The World Health Organization (WHO) defines maternal mortality as the death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration and site of the pregnancy, from any cause related to or aggravated by the pregnancy or its management (but not from accidental or incidental causes). The primary focus is on the period immediately surrounding pregnancy and childbirth.

**Why the Correct Answer is Right**
The correct answer is **During lactation 8th month** because the WHO definition of maternal mortality explicitly excludes deaths occurring during the postpartum period beyond 42 days, including those during the prolonged postpartum period. This definition emphasizes the critical importance of distinguishing between maternal and non-maternal deaths, particularly in the context of international health statistics and maternal health policy.

**Why Each Wrong Option is Incorrect**
**Option A:** Following abortion is indeed a recognized cause of maternal death, as it falls within the defined period of maternal mortality.

**Option B:** During lactation, the first month (Puerperal) is also considered part of the maternal mortality period, as it may be related to complications arising from the pregnancy or childbirth.

**Option D:** During the last trimester due to Antepartum Haemorrhage (APH) is a valid cause of maternal death, as it occurs during the pregnancy itself.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the WHO definition of maternal mortality serves as a critical benchmark for monitoring global progress in reducing maternal mortality rates and improving maternal health outcomes. This definition helps guide health policy and resource allocation efforts aimed at addressing the leading causes of maternal death worldwide.

**✓ Correct Answer: C. During lactation 8th month**