To explore the characteristics of 'sawtooth shunts (STS)' following intravitreal anti-vascular endothelial growth factors (anti-VEGF) for aggressive posterior retinopathy of prematurity (AP-ROP).Prospective observational study.In a prospective observational study, 45 eyes of 24 babies receiving intravitreal anti-VEGF for AP-ROP or hybrid ROP were analyzed. Anti-VEGF molecule and doses: bevacizumab (0.62 mg or ½ IVB, n = 30 eyes; 0.25 mg or 1/5IVB, n = 9 eyes; 0.12 mg or 1/10 IVB, n = 1 eye); or ranibizumab (0.25 mg or ½IVR, n = 3 eyes; 0.1 mg or 1/5IVR, n = 2 eyes). They were followed every 1-2 week till disease regression with or without laser treatment. Development of STS, its variants, characteristics, timeline, and final outcomes was analyzed.STS occurred in 26 (57.7%) eyes at 1-6 weeks following anti-VEGF injections and persisted for 1-14 weeks. While the shunt regressed spontaneously in half of the treated eyes (n = 13) with anti-VEGF alone, the other half (n = 13) required additional laser because of either non-compliance (n = 9) or recurrence (n = 4).The STS was observed to be an important retinal vascular change seen in infants treated with intravitreal anti-VEGF at half adult doses. It warrants further studies to explore the association between STS and its association with disease recurrence or regression.