The North American Fetal Therapy Network Consensus Statement

Abstract

Owing to vascular connections within a single placenta, monochorionic gestations present distinctive prenatal management challenges. Complications that can arise as a result of unbalanced hemodynamic exchange (twin-twin transfusion syndrome and twin anemia polycythemia sequence) and unequal placental sharing (selective fetal growth restriction) should be kept in mind while prenatal management is being planned. Because of unique monochorionic angioarchitecture, what happens to one twin can directly affect the other. Death of one twin can result in death or permanent disability of the co-twin. Early detection of these unique disease processes through frequent ultrasonographic surveillance may allow the opportunity for earlier referral, intervention, or both and potentially better outcomes. Therefore, monochorionic gestations should be managed differently than dichorionic gestations or singletons. The purpose of this document is to present in detail methods for monitoring and management of uncomplicated monochorionic gestations and to review the evidence for the roles of these methods for detection of complications in clinical practice. Finally, we present evidence-based and expert opinion-supported recommendations developed by the North American Fetal Therapy Network for the diagnosis, surveillance, and delivery of uncomplicated monochorionic gestations.

Validation of a Single-Nucleotide Polymorphism-Based Non-Invasive Prenatal Test in Twin Gestations: Determination of Zygosity, Individual Fetal Sex, and Fetal Aneuploidy

“…Monochorionic (MC) twins account for ~20% of twin gestations [3,4] and have higher rates of major structural defects, miscarriage, preterm delivery, and selective fetal growth restriction compared to dichorionic (DC) twins [5]. Of particular importance, MC twins are at high risk for twin-to-twin transfusion syndrome (TTTS), which accounts for more than one-third of perinatal MC twin deaths [6,7].…”

Perinatal outcomes in Finnish twins: a retrospective study

“…This finding also emphasizes the outstanding neonatal care in Finland, although in rare cases potential mislabeling of twins may slightly alter our results. In monochorionic twins, the higher PNM and morbidity are particularly due to twin-to-twin transfusion syndrome [27]. We were unable to analyze the differences between chorionicities because this information is still not collected into the Finnish registers.…”

Review of International Clinical Guidelines Related to Prenatal Screening during Monochorionic Pregnancies

“…While the majority of resources also mentioned nuchal translucency (NT) screenings (Table 2), some noted that NT discordance might be interpreted as an early sign of SFGR and/or TTTS, which could complicate the typical interpretation of NT screening results [12,17,23,32,33]. However, others commented that early NT discordance is not considered predictive of TTTS and should not be treated as such [26,27].…”

“…Approximately half (n = 13, 52%) of the resources recommended routine screening for the complication of TAPS, via MCA-PSV Doppler, as part of the biweekly ultrasound regimen [8,11,12,[15][16][17]20,23,25,[28][29][30]33]. Obtaining MCA-PSV multiples of the normal median (MoM) values of <1.0 and >1.5 [17,20,25,27], indicating risk of TAPS, were generally reported, although some reported looking for the larger MoM range of <0.8 and >1.5 [8,11,20,29,31].…”

“…Several sources reported that screening for TAPS should only occur post-TTTS laser surgery [31] or if other complications are occurring [26,27] and should not be part of routine screening. Some resources reported that screening was controversial [29] and could not make a statement for or against TAPS screening [22] or the use of calculation of MCA-PSV MoM [23]. However, still other resources indicated that screening for TAPS at any time using MCA-PSV Doppler has not been shown to improve outcomes and therefore could not be recommended [32].…”