**Core Concept**
Maternal mortality rate (MMR) is a critical indicator of the quality of healthcare and outcomes for pregnant women. It is defined as the number of deaths due to pregnancy-related causes per 100,000 live births. The calculation of MMR requires a specific time frame to determine the numerator, which includes deaths from pregnancy-related causes.

**Why the Correct Answer is Right**
The World Health Organization (WHO) and other global health authorities define maternal mortality as deaths due to pregnancy-related causes within 42 days of termination of pregnancy, irrespective of the duration and site of the pregnancy, from now on or from the date of abortion, or miscarriage. This 42-day period is crucial in identifying deaths related to pregnancy complications, such as hemorrhage, eclampsia, and sepsis. The specific time frame of 42 days ensures that deaths due to direct or indirect causes related to pregnancy are accurately captured and reported.

**Why Each Wrong Option is Incorrect**
**Option A:** Calculating MMR till delivery would underestimate the number of deaths related to pregnancy complications, as it would not account for deaths occurring after delivery.
**Option B:** Including deaths till 1 week after delivery is also insufficient, as it would still miss deaths occurring later in the postpartum period.
**Option D:** This option is incorrect because there is a correct answer among the options provided.

**Clinical Pearl / High-Yield Fact**
Remember that the 42-day time frame for calculating maternal mortality rate is critical in accurately capturing deaths due to pregnancy-related causes, and this period should be strictly adhered to in all maternal mortality audits and reporting.

**✓ Correct Answer: C. Till 42 days after delivery**