## **Core Concept**
Labour is a physiological process that involves the delivery of a baby through the birth canal. Prolonged labour, also known as obstructed labour, is a condition where the labour process extends beyond the normal duration, potentially leading to maternal and fetal complications. The normal duration of labour varies among individuals, but there are established guidelines to define prolonged labour.

## **Why the Correct Answer is Right**
The correct answer defines the duration beyond which labour is considered prolonged. According to the World Health Organization (WHO) and other obstetric guidelines, labour is considered prolonged in a primigravida (a woman pregnant for the first time) if the active phase of the first stage lasts more than 12 hours, or the second stage lasts more than 2 hours without epidural anesthesia or more than 3 hours with epidural anesthesia. For a multigravida (a woman who has been pregnant more than once), the active phase of the first stage should not exceed 14 hours. However, a commonly used and simpler criterion for prolonged labour in the first stage for primigravidas is 14 hours and for the second stage is 2 hours.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately reflect the commonly used criteria for defining prolonged labour.
- **Option B:** This option is incorrect as it does not match the standard definitions used in obstetrics for prolonged labour.
- **Option D:** This option is incorrect because it does not align with established guidelines for the duration of labour.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the diagnosis of prolonged labour requires careful assessment of the labour progress, including cervical dilatation and fetal station. Prolonged labour can lead to significant maternal and fetal morbidity, including uterine rupture, fetal distress, and postpartum hemorrhage. Early recognition and appropriate management are crucial.

## **Correct Answer:** C.