The transition between phase 1 and phase 2 in the development of ROP peaks at which postmenstrual age range?

• A. 30 to 32 weeks
• B. 38 to 40 weeks
• C. 34 to 36 weeks
• D. 42 to 44 weeks

Answer: (C)

The question tests timing of the switch from the initial arrest of retinal vascular growth to the proliferative neovascular phase in retinopathy of prematurity. After preterm birth, the retina’s vessels are disrupted by oxygen exposure (Phase I), and as the retina continues to mature postnatally, it becomes relatively hypoxic, triggering new vessel growth (Phase II). The transition between these two phases occurs most prominently in the late preterm period, around thirty-four to thirty-six weeks postmenstrual age. This timing reflects when the retina has grown enough to create hypoxic drive for neovascularization but hasn’t completed normal vascular development if the infant remains premature. In other words, the mid-to-late preterm PMA window is when Phase I ends and Phase II begins.