**Core Concept**
Retinopathy of Prematurity (ROP) is a disease of the eye affecting prematurely born babies, characterized by abnormal growth of blood vessels in the retina. Early detection through screening is crucial to prevent vision loss. The timing of ROP screening is critical, as it depends on the gestational age and postnatal age of the infant.

**Why the Correct Answer is Right**
ROP screening should be performed between 31 and 33 weeks of postmenstrual age (PMA), which is equivalent to 4-6 weeks of chronological age in a 28-week gestation baby. This allows for early detection of ROP in high-risk infants. The screening is typically done by an ophthalmologist or an experienced pediatrician using indirect ophthalmoscopy.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because ROP screening should not be delayed beyond 6 weeks of chronological age in a 28-week gestation baby.
**Option B:** This option is incorrect because ROP screening should not be performed before 31 weeks of PMA, as the risk of ROP is lower before this age.
**Option C:** This option is incorrect because ROP screening should not be performed at the same time as the initial treatment for sepsis, as the infant may be too unstable for the procedure.

**Clinical Pearl / High-Yield Fact**
ROP screening should be performed by an experienced healthcare provider to ensure accurate detection and treatment of the disease. A delay in ROP screening can lead to vision loss in high-risk infants.

**Correct Answer: D. 4-6 weeks.**