**Question:** A new born can lose up to ______ % of birth weight in the first week of life:

A. 10%
B. 7%
C. 15%
D. 20%

**Core Concept:** Birth weight loss in neonates

In the first week of life, neonates undergo physiological weight loss due to several factors, including:

1. **Increased water loss:** Neonates have a higher surface area-to-mass ratio compared to adults, leading to increased water loss via sweat and respiration, contributing to a decrease in body weight.
2. **Increased energy expenditure:** Newborns have a higher energy requirement due to increased heart rate, breathing rate, and muscle tone.
3. **Increased urine output:** Neonates excrete more urine than adults, leading to a loss of water and electrolytes.

**Why the Correct Answer is Right:**

**Correct Answer: B. 7%**

Neonates typically lose approximately 7% of their birth weight in the first week of life. This is considered within the normal range and does not require intervention unless the weight loss is excessive or accompanied by symptoms like decreased feeding, respiratory distress, or poor overall condition.

**Why Each Wrong Option is Incorrect:**

A. 10% - This is excessive weight loss and should prompt clinical evaluation of the neonate.
C. 15% - This is also excessive and associated with significant clinical concerns.
D. 20% - This is highly concerning, and immediate medical attention should be sought.

**Clinical Pearl:** Monitoring neonatal weight loss is crucial for determining normal vs. abnormal weight loss and ensuring the newborn's overall health and wellbeing. If weight loss is excessive or accompanied by clinical signs, further evaluation is warranted.