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Sound waves to separate twin placentas?

High-energy sound waves could treat a potentially deadly complication of some twin pregnancies TTTS or Twin-Twin Transfusion Syndrome, affecting one in seven identical twin pregnancies.


Twin-Twin Transfusion Syndrome leads to one baby growing much larger than the other due to abnormal blood vessel growth in the placenta.

Some identical twins share a placenta, which provides twin babies with equal amounts of oxygen and nutrients carried in the blood. However in TTTS the shared placenta contains abnormal blood vessels causing more blood to flow to one baby, leaving the other deprived. This can result in complications such as premature birth, handicap or even death of one or both twins.

Severe cases can be treated by using a laser to destroy the abnormal blood vessels, so that each baby has a separate supply of oxygen and nutrients. However, this involves making a small hole in the womb and carries a risk of infection or miscarriage, explains Dr Christoph Lees, senior author from the Department of Surgery and Cancer at Imperial.


"Although this is very early-stage research, it shows the procedure can successfully destroy blood vessels in the placenta - and could potentially stop abnormal blood flow between twin babies. We now hope to continue developing this HIFU procedure, translate these findings to humans, and work towards human trials."

Christoph Lees MD MRCOG, Faculty of Medicine, Department of Surgery & Cancer, Obstetrics and Fetal Medicine at Imperial College London, and senior author.

The study is published in the journal Science Translational Medicine.

High Energy Focused Ultrasound (HIFU) can be selectively targeted to destroy placental blood vessels — potentially enabling the split of the placenta into two, without need for an invasive procedure. The technique creates a beam of high energy sound waves that generate heat, and kill cells. A similar procedure is already used to treat prostate cancer and fibroids.

To establish whether the procedure could destroy placental blood vessels, the team used the technique on 11 anesthetised pregnant sheep - five had the HIFU procedure while six had a placebo procedure.

Although the sheep did not carry twins, the blood vessels in the sheep placenta have a similar structure to blood vessels in the human placenta, enabling the researchers to assess whether the HIFU could separate the placenta in TTTS. Sheep fetuses and human infants are a similar size.

The results showed the technique was successful, and could destroy blood vessels without damage to the fetus. Researchers used the HIFU probe against the wall of the uterus, through an incision in the abdomen - and through further experiments, showed the procedure works through the skin.


"Although this is very early-stage research, it shows the procedure can successfully destroy blood vessels in the placenta to potentially stop abnormal blood flow between twin babies.

"We now hope to continue developing this HIFU procedure, translate these findings to humans, and work towards human trials."

Christoph Lees MD MRCOG


Because the technique is non-invasive, the team believes the procedure could potentially be performed at an earlier stage in pregnancy, to further reduce chance of complications. The laser procedure is usually performed at around five months of pregnancy, once the womb is big enough to accommodate the laser being inserted. However, the current study suggests the procedure may work even earlier, at around three-four months into the pregnancy.

Abstract
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.

Copyright 2016, American Association for the Advancement of Science

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Jul 18, 2016   Fetal Timeline   Maternal Timeline   News   News Archive   



Some identical twins share a placenta, providing both babies with equal amounts of oxygen and nutrients. However in TTTS the shared placenta causes more blood to flow to one baby, leaving the other deprived.
Image Credit: Public Domain


 


 

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