**Core Concept**
The World Health Organization (WHO) provides a standardized definition for abortion, which is essential for global health statistics, research, and policy-making. This definition is based on the medical and social context of the pregnancy termination.

**Why the Correct Answer is Right**
The WHO defines abortion as "the termination of pregnancy, as a result of intercession before viability or of a spontaneous process, before the fetus reaches the viability threshold." This definition encompasses both induced and spontaneous abortions. The term "viability" refers to the point at which a fetus can survive outside the uterus with or without medical assistance, typically around 24 weeks of gestation. The WHO definition is comprehensive, considering both medical and spontaneous terminations of pregnancy.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the context of the pregnancy termination, including the gestational age or the method used.
**Option B:** This option is incorrect because it only mentions the termination of pregnancy but does not provide any additional context, such as the gestational age or the method used.
**Option C:** This option is incorrect because it only mentions the termination of pregnancy before the fetus reaches viability, but it does not account for spontaneous processes.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the WHO definition of abortion is crucial for global health statistics, research, and policy-making. Understanding this definition helps healthcare professionals and policymakers address the complex issues surrounding abortion and reproductive health.

**Correct Answer:** A. The termination of pregnancy, as a result of intercession before viability or of a spontaneous process, before the fetus reaches the viability threshold.