BACKGRAUND
Selective fetal growth restriction (sFGR) is one of the common diseases of monochorionic diamniotic (MCDA) twin pregnancies, resulting in many adverse outcomes. MCDA twin pairs are predisposed to various pregnancy complications due to the unique placental angioarchitecture of monochorionicity.
OBJECTIVE
This study aimed to explore the placenta histopathological characteristics of sFGR in monochorionic diamniotic twin pregnancies and to explain placental dye injection studies to document the vascular anastomoses and placental sharing. We elaborate on the different types of anastomoses, the importance of how the placenta is divided between the twins, and the angioarchitecture in selective fetal growth restriction.
MATERIALS AND METHODS
This was a retrospective cohort study of monochorionic diamniotic twin pregnancies with sFGR between January 2021 and September 2022. A total of 20 placentas with sFGR and 30 placentas without were retrospectively analyzed after dye injection. Classification of the cohort as sFGR or non-sFGR was performed using three different definitions: (1) estimated fetal weight (EFW) of one twin <10th centile and intertwin EFW discordance >25%, according to the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) (Definition A); (2) EFW of one twin <3rd centile, according to the solitary criterion for sFGR reported in a Delphi consensus (Definition B); and (3) presence of at least two of four of the following criteria: EFW of one twin <10th centile, abdominal circumference of one twin <10th centile, intertwin EFW discordance of ≥25% and umbilical artery pulsatility index of the smaller twin >95th centile, according to the contributory criteria for sFGR in monochorionic diamniotic twin pregnancies reported in the Delphi consensus (Definition C).
RESULTS
A total of 50 placentas were analyzed. The incidence of anastomosis in the discordant group (91%) was significantly higher than that in the concordant group (51%). Abnormal umbilical cord insertion was significantly more common in the discordant group (60.2%) than in the concordant group (36%, p<0.001). Placental sharing discordance was seen no more frequently in the discordant group than in the concordant group.
CONCLUSIONS
Anastomoses and abnormal umbilical cord insertion of the smaller twin are independent risk factors for birthweight discordance in MCDA twin. Pathologic placental examination after delivery can help in assessing the presence of placental and umbilical cord abnormalities, as well as providing information about chorionicity and gaining insight into the potential mechanisms of disease affecting twin gestations.
