**Question:** By 2 week of age, infants normally show all of the following signs EXCEPT

A. Persistent fetal breathing movements
B. Increased startle reflex
C. Facial grimacing during feeding
D. Rapid eye movement (REM) sleep

**Core Concept:** In infants, certain physiological and behavioral changes occur during the first two weeks of life, which are indicative of maturation and adaptation to extrauterine life.

**Why the Correct Answer is Right:**

By 2 weeks of age, infants exhibit several physiological and behavioral changes, which are essential for their adaptation to extrauterine life. These changes include:

1. **Persistent fetal breathing movements (Option A):** These are the irregular, non-patterned breathing movements that occur in the newborn during sleep. By two weeks of life, these movements become more rhythmic and patterned, resembling adult-like breathing.
2. **Increased startle reflex (Option B):** The startle reflex is a protective reflex triggered by sudden or unexpected stimuli. In infants, the startle reflex is initially exaggerated and becomes less intense over time as the infant adapts to their new environment.
3. **Facial grimacing during feeding (Option C):** Infants may exhibit facial grimacing during feeding due to the orogastric reflex, which is a protective mechanism triggered by the passage of food into the stomach. This reflex is common in newborns and may persist into the first few weeks of life.
4. **Rapid eye movement (REM) sleep (Option D):** REM sleep is a stage of sleep characterized by increased brain activity and eye movements. Infants undergo REM sleep soon after birth and continue to experience it throughout their life. Although the frequency of REM sleep decreases over time, it remains a vital component of sleep in infants.

**Why Each Wrong Option is Incorrect:**

A. **Persistent fetal breathing movements (Option A):** By 2 weeks of age, infants typically exhibit more adult-like breathing patterns, making this option incorrect.
B. **Increased startle reflex (Option B):** Infants generally exhibit a decreased startle reflex as they adapt to their new environment.
C. **Facial grimacing during feeding (Option C):** Although facial grimacing during feeding is common in newborns, it usually resolves by the first few weeks of life, making this option incorrect.
D. **Rapid eye movement (REM) sleep (Option D):** REM sleep remains an essential part of infants' sleep pattern, despite a decrease in frequency over time.

**Clinical Pearl:**
Monitoring the development and maturation of these physiological and behavioral changes in infants is crucial for healthcare providers to assess the child's overall health and wellbeing. Prompt recognition of any abnormalities in these signs can help identify potential developmental delays or medical conditions that require further evaluation and intervention.