Infants who meet at-risk criteria for ROP should have their initial examination by the later of:

• A. 31 weeks postmenstrual age or 4 weeks after birth
• B. 30 weeks postmenstrual age or 5 weeks after birth
• C. 32 weeks postmenstrual age or 3 weeks after birth
• D. 33 weeks postmenstrual age or 6 weeks after birth

Answer: (A)

Determining when to screen for ROP hinges on balancing retinal development with early detection. The initial exam should be done at the later of 31 weeks postmenstrual age or 4 weeks after birth. This approach ensures you don’t screen too early, before the retina has developed enough to show early signs, while still catching potentially progressive disease within a window where treatment is most effective.

For example, a baby born at 28 weeks gestation would reach 4 weeks after birth at about 32 weeks PMA, so the exam would occur around 32 weeks PMA. A baby born at 33 weeks would have 4 weeks after birth at 37 weeks PMA, so the exam would be scheduled at about 37 weeks PMA. This flexibility keeps screening aligned with each infant’s maturation and postnatal age, optimizing timing across varying degrees of prematurity.

Other proposed timings either come too early relative to retinal development or delay screening beyond when ROP could first be detected, which is why the guideline uses the later of these two thresholds.