Fig. 2. Description of new clinical classification system for cesarean scar pregnancy. A–C. Type I is defined as the implantation of a gestational sac within the cesarean scar, with anterior myometrium thickness greater than 3 mm regardless of the size of the gestational sac. D–F. Type IIa is defined as anterior myometrium thickness between 1 and 3 mm and average diameter of the gestational sac or mass 30 mm or less. G–I. Type IIb is defined as anterior myometrium thickness between 1 and 3 mm and average diameter of the gestational sac or mass greater than 30 mm. J–L. In type IIIa, the gestational sac bulges out under the cesarean scar, with anterior myometrium thickness 1 mm or less and average diameter of the gestational sac or mass 50 mm or less. M–O. Type IIIb is defined as anterior myometrium thickness 1 mm or less and average diameter of the gestational sac or mass greater than 50 mm.

Ban. Cesarean Scar Ectopic Pregnancy Classification System. Obstet Gynecol 2023.