Selective FGR in Monochorionic Twin Pregnancy: Gratacos Classification (Types I–III)
Selective fetal growth restriction (sFGR) in monochorionic twin pregnancy is classified according to the Gratacos et al. system, described in the publication: «A classification system for selective intrauterine growth restriction in monochorionic pregnancies according to umbilical artery Doppler flow in the smaller twin» (Ultrasound Obstet Gynecol. 2007;30(1):28-34). The classification is based on assessment of blood flow in the umbilical artery of the smaller fetus.
Classification Principle
The Gratacos classification identifies three types of sFGR depending on the pattern of diastolic flow in the umbilical artery of the smaller of the two fetuses. Specific Doppler characteristics of each type (I–III) are not detailed in the provided fragments [requires clarification].
Clinical Significance of Type II
Type II sFGR is considered separately in the context of endoscopic laser coagulation of the placenta in monochorionic diamniotic twins (Peeva G. et al. Fetal Diagn Ther. 2015;38(2):86-93). This indicates a relationship between the classification type and the choice of invasive management strategy.
Management Strategy and Outcomes
Perinatal outcomes in monochorionic twin pregnancy complicated by sFGR, depending on the management method, have been analyzed in a systematic review and meta-analysis (Townsend R, D'Antonio F, Sileo FG et al. Ultrasound Obstet Gynecol. 2019;53(1):36-46). The role of ultrasound in twin pregnancy management is also reflected in the updated ISUOG recommendations (ISUOG Practice Guidelines: role of ultrasound in twin pregnancy, 2025).
Differences with Dichorionic Twin Pregnancy
Diagnosis, natural course, and perinatal outcome of sFGR in dichorionic twin pregnancy are described separately (Antonakopoulos N, Pateisky P, Liu B et al., 2020), since most published literature on sFGR is focused specifically on monochorionic pregnancies.
Frequently asked questions
On what is the Gratacos classification based?
On assessment of blood flow in the umbilical artery of the smaller fetus in monochorionic pregnancy (Gratacos E. et al. Ultrasound Obstet Gynecol. 2007;30(1):28-34).
How many types does the classification identify?
Three types (I–III) depending on Doppler blood flow in the umbilical artery of the smaller fetus.
Which type is associated with laser coagulation?
Type II sFGR is considered in the context of endoscopic laser coagulation of the placenta in monochorionic diamniotic twins (Peeva G. et al. Fetal Diagn Ther. 2015).
Does sFGR differ in dichorionic twin pregnancy?
Yes, its diagnosis and outcomes are described separately (Antonakopoulos N. et al., 2020); the majority of literature on sFGR focuses on monochorionic pregnancies.