Research ArticlePregnancy

Noninvasive high-intensity focused ultrasound treatment of twin-twin transfusion syndrome: A preliminary in vivo study

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Science Translational Medicine  13 Jul 2016:
Vol. 8, Issue 347, pp. 347ra95
DOI: 10.1126/scitranslmed.aaf2135

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Splitting the babies

Twin-twin transfusion syndrome is a complication of some twin pregnancies, where abnormal connections between the twins’ placental blood vessels result in unequal sharing of blood flow, with potentially lethal consequences. Although it is possible to separate the twins’ vasculature using fetoscopic laser occlusion of the connecting blood vessels, it is an invasive treatment with a high risk of complications. Shaw et al. used a sheep model of pregnancy to demonstrate the feasibility and relative safety of using high-intensity focused ultrasound to ablate blood flow through individual placental vessels. The authors used only healthy pregnant sheep, and the procedure still required surgical intervention to reach the uterus, but this approach may eventually offer a safer treatment alternative for human patients.


We investigated the efficacy, maternofetal responses, and safety of using high-intensity focused ultrasound (HIFU) for noninvasive occlusion of placental vasculature compared to sham treatment in anesthetized pregnant sheep. This technique for noninvasive occlusion of placental vasculature may be translatable to the treatment of conditions arising from abnormal placental vasculature, such as twin-twin transfusion syndrome (TTTS). Eleven pregnant sheep were instrumented with maternal and fetal arterial catheters and time-transit flow probes to monitor cardiovascular, acid-base, and metabolic status, and then exposed to HIFU (n = 5) or sham (n = 6) ablation of placental vasculature through the exposed uterine surface. Placental vascular flow was occluded in 28 of 30 targets, and histological examination confirmed occlusion in 24 of 30 targets. In both HIFU and sham exposures, uterine contact reduced maternal uterine artery flow, but delivery of oxygen and glucose to the fetal brain remained normal. HIFU can consistently occlude in vivo placental vessels and ablate blood flow in a pregnant sheep model. Cardiovascular and metabolic fetal responses suggest that the technique is safe in the short term and potentially translatable to human pregnancy.

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