Background

Twin reversed arterial perfusion (TRAP) sequence is a rare complication of monochorionic multiple gestation pregnancies, in which the pump twin provides hemodynamic support to a nonviable co-twin (acardius). Fetal magnetic resonance imaging (MRI) is used to detect pump twin abnormalities, particularly brain ischemia, prior to fetal intervention to interrupt umbilical blood flow to the acardius.

Objective

To summarize the imaging findings of TRAP sequence pregnancies in a large series.

Materials and methods

A single-center retrospective review was performed of all TRAP sequence pregnancies referred for fetal MRI (2004–2021). Fetal MRI, ultrasound, and echocardiography data were collected.

Results

Eighty-eight TRAP sequence pregnancies with MRI were included (mean gestational age, 19.8±2.8 weeks). Demise of the pump twin was noted in two pregnancies at the time of MRI. By MRI, 12% (10/86) of live pump twins had abnormalities, including 3% (3/86) with brain abnormalities and 9% (8/86) with extra-cranial abnormalities. By echocardiography, 7% (6/86) of pump twins had structural cardiac abnormalities. Three acardius morphological subtypes were identified by MRI: acephalus (55%, 48/88), anceps (39%, 34/88), and amorphous (7%, 6/88). The mean ultrasound acardius to pump twin ratio A/P ratio, calculated for each twin pair as the ratio of the acardius trunk (and head, if present) plus limb volume to the pump twin estimated fetal weight) differed among the three acardius subtypes (P=.03). The mean A/P ratio moderately correlated with pump twin cardiothoracic ratio and combined cardiac output (Pearson’s r=0.45 and 0.48, respectively, both P<.001).

Conclusion

Fetal MRI of TRAP sequence pregnancies found anomalies in a substantial number of pump twins. The three acardius subtypes differed in A/P ratio, which moderately correlated with the pump twin cardiothoracic ratio and combined cardiac output.

Graphical abstract

背景

双胎逆向动脉灌注 (TRAP) 序列是单绒毛膜多胎妊娠的一种罕见并发症，其中泵双胞胎为无法存活的双胞胎（无心胎）提供血流动力学支持。胎儿磁共振成像 (MRI) 用于在胎儿干预之前检测泵双胞胎异常，特别是脑缺血，以中断流向心室的脐血。

客观的

总结一系列 TRAP 序列妊娠的影像学结果。

材料和方法

对所有转诊进行胎儿 MRI 的 TRAP 序列妊娠（2004-2021 年）进行了单中心回顾性审查。收集胎儿 MRI、超声和超声心动图数据。

结果

纳入 88 例进行 MRI 检查的 TRAP 序列妊娠（平均孕龄，19.8±2.8 周）。MRI 检查时发现两次妊娠中双胎泵死亡。通过 MRI 检查，12% (10/86) 的活泵双胞胎存在异常，其中 3% (3/86) 存在脑部异常，9% (8/86) 存在颅外异常。通过超声心动图检查，7% (6/86) 的泵双胞胎存在结构性心脏异常。通过 MRI 鉴定出三种无心形亚型：无心形 (55%, 48/88)、无心形 (39%, 34/88) 和无定形 (7%, 6/88)。平均超声心电图与泵双胞胎比率 A/P 比值是针对每对双胞胎计算的，计算为心电图躯干（和头部，如果存在）加上肢体体积与泵双胞胎估计胎儿重量的比率，在三种心电图亚型之间存在差异（P =.03）。平均 A/P 比值与泵双心胸比和合并心输出量中度相关（Pearson's r分别 =0.45 和 0.48，均P <.001）。

结论

TRAP 序列妊娠的胎儿 MRI 发现大量泵双胞胎存在异常。三种无心室亚型的 A/P 比值不同，该比值与泵双心胸比和组合心输出量中度相关。

图形概要