**Question:** Preterm infant is defined as -

A. Infant born before 37 weeks of gestation
B. Infant born before 28 weeks of gestation
C. Infant born after 22 weeks of gestation
D. Infant born after 28 weeks of gestation

**Core Concept:** Preterm birth refers to the delivery of a baby before it is fully developed, typically before 37 completed weeks of gestation. Gestational age is calculated based on the first day of the woman's last menstrual period (LMP).

**Why the Correct Answer is Right:** Preterm infants are classified based on their gestational age, which is crucial for understanding their health risks and management strategies. Preterm birth occurs when a baby is born before 37 weeks of gestation, which is defined as **A**. This age is chosen because it reflects the development milestones and the increased risks associated with birth before this critical period.

**Why Each Wrong Option is Incorrect:**

**Option B:** Infants born before 28 weeks of gestation are considered extremely preterm, which carries significantly higher risks compared to preterm infants born between 28-37 weeks. While important, option B is too specific and does not encompass the broader definition of preterm birth.

**Option C:** Infants born after 22 weeks of gestation may have a chance of survival, but they are still at high risk for severe complications, including disabilities and developmental issues. This option is too narrow and does not encompass the broader definition of preterm birth.

**Option D:** Infants born after 28 weeks of gestation are considered moderately preterm, which is associated with lower risks compared to extremely preterm infants born before 28 weeks. This option is too specific and does not encompass the broader definition of preterm birth.

**Correct Answer:** Preterm infants born between 28-37 weeks of gestation are **A** preterm infants, which are at increased risk for various complications but have better outcomes compared to infants born before 28 weeks. This range covers the majority of preterm infants and is more relevant for clinical decision-making and research purposes.

**Core Concept:** Preterm birth is a critical aspect of neonatal medicine, as it affects millions of infants globally and has significant implications for their overall health and development. Understanding gestational age and the associated risks is essential for healthcare providers to provide appropriate care and interventions for these vulnerable infants.