Twin twin transfusion syndrome management and outcome

The three primary approaches to management of TTTS are expectant management, fetoscopic laser ablation ofanastomotic vessels, and amnioreduction.. MANAGEMENT OF QUINTERO STAGE I — The ch

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Official reprint from UpToDate

Twintwin transfusion syndrome: Management and outcome

Authors: Anthony Johnson, DO , Ramesha Papanna, MD, MPH

Section Editors: Deborah Levine, MD , Louise WilkinsHaug, MD, PhD

polycythemia sequence: Pathogenesis and diagnosis", section on 'Monitoring for TTTS'.)

The three primary approaches to management of TTTS are expectant management, fetoscopic laser ablation ofanastomotic vessels, and amnioreduction. Selective reduction is another option, but is rarely performed in theabsence of discordant malformations or severe selective fetal growth restriction. The choice of approach depends

on the Quintero stage, maternal symptoms and signs, gestational age, and availability of requisite technical

expertise

This topic will review the management and outcome of TTTS. The pathogenesis, clinical manifestations,

diagnosis, and monitoring for TTTS are discussed separately. (See "Twintwin transfusion syndrome and twinanemia polycythemia sequence: Pathogenesis and diagnosis".)

MANAGEMENT OF QUINTERO STAGE I — The choice of therapy for Quintero stage I TTTS is based primarily

on severity of maternal discomfort from uterine distention and on cervical length. No randomized trials have

compared treatment approaches for stage I TTTS. A systematic review concluded that the optimal initial

management of stage I TTTS "remains in equipoise" [1]. In this review, the pooled incidence of progression instage I TTTS was 27 percent (95% CI 1639)

Women with no or tolerable symptoms and a normal cervical length

Choice of therapy — For women with Quintero stage I (table 1) TTTS and no maternal symptoms or

tolerable symptoms and transvaginal cervical length >25 mm, we avoid intervention and monitor TTTS status withweekly ultrasound examinations to detect progression to more severe disease. In addition to the morbidity

associated with any intervention, unnecessary intervention can affect therapeutic options later in pregnancy ifintervention becomes indicated because of progressive disease. For example, amnioreduction performed as afirstline treatment of minimally symptomatic stage I disease can result in an inadvertent septostomy or bloodyamniotic fluid, which would make subsequent laser treatment difficult to undertake when indicated because ofworsening TTTS

This approach is based on limited but reassuring data of the outcome of welldefined stage I disease in the

absence of any intervention. In a 2013 systematic review of seven observational studies including 262 twin

pregnancies, expectantly managed stage I TTTS resolved or remained stable in 85 percent of cases [2]. Thesurvival rate with expectant management was 86 percent versus 85 percent with laser therapy and 77 percent

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with amnioreduction. Outcomes were similar when laser therapy was a secondchoice rather than a firstchoicetreatment, which suggests that delaying this intervention does not worsen the prognosis

In contrast, a subsequent retrospective observational study by the North American Fetal Therapy Network

reported poor outcomes with expectant management of stage I TTTS [3]. In the 49 expectantly managed stage ITTTS pregnancies, 8 percent remained stable, 22 percent regressed, 60 percent progressed to a more severestage, and 10 percent resulted in a spontaneous previable preterm birth. The mean duration from diagnosis ofstage I TTTS to a change in status was 11.1 days ±14.3 days; in those cases that progressed, the mean durationwas 9 days. Both amnioreduction and laser therapy at stage I TTTS decreased the likelihood of no survivors

(odds ratio [OR] 0.11, 95% CI 0.020.68 and OR 0.07, 95% CI 0.010.37, respectively) compared with expectantmanagement

An international randomized trial comparing expectant management with laser ablation in management of stage ITTTS is underway and should provide better data on which to base recommendations regarding the appropriaterole of early intervention at the onset of TTTS [4

Prenatal followup and care — We monitor pregnancies with stage I TTTS and no maternal symptoms ortolerable symptoms and transvaginal cervical length >30 mm for disease progression with ultrasound:

If TTTS stage and symptoms remain stable, the American College of Obstetricians and Gynecologists and theInternational Society for Ultrasound in Obstetrics and Gynecology suggest scheduling delivery at 34 to 37 weeks

Amniotic fluid volume is assessed weekly

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Fetal growth is assessed every three to four weeks. If selective fetal growth lag is identified (ie, one fetus withestimated fetal weight <10 percentile), Doppler blood flow studies of the umbilical artery and ductus venousare obtained weekly

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Beginning at 28 weeks, Doppler blood flow studies to assess middle cerebral artery peak systolic velocities(MCAPSV) are obtained weekly. Discordant values are indicative of twin anemia polycythemia sequence(TAPS), a milder form of TTTS that occurs spontaneously in 5 percent of monochorionic twins. Discordancy

is defined as MCAPSV >1.5 multiples of the median (MoM) in one fetus in conjunction with a value of <1.0MoM in the other. TAPS is discussed in more detail below. (See 'Twin anemia polycythemia sequence'

below.)

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Beginning at 30 weeks, biophysical profile scores are obtained weekly

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The procedure is described below. (See 'Fetoscopic laser ablation of anastomotic vessels' below.)

Prenatal followup and care after laser therapy — There are few data on which to base specific

recommendations for prenatal followup and care after laser therapy. We have adopted the following protocol forroutine postlaser fetal surveillance:

We do not routinely order magnetic resonance imaging (MRI) postlaser at 30 to 32 weeks of gestation. Two to 6percent of neonates will have an ischemic hemorrhagic lesion; however, one study noted that 82 percent of thesecases were detected by ultrasound prior to MRI [14]. In addition, monochorionic twins are known to have whitematter injury, even those without known diagnosis of TTTS, so if an injury is seen, it will not be known whether it isdue to the procedure or not. Lastly, few centers have qualified individuals onsite to read/interpret a fetal MRI.MRI may be informative in cases with a cotwin demise postlaser. In theory, all vascular communications betweenthe twins should be closed so the surviving cotwin should not be at risk of hypotension/emboli at the time of thedemise, but since recurrent TTTS is possible, International Society of Ultrasound in Obstetrics and Gynecology(ISUOG) guidelines suggest consideration of imaging (MRI) 4 to 6 weeks after a demise is detected [11]

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Fetal weight is estimated every three to four weeks to identify severe growth lag (ie, one fetus with estimatedfetal weight <10 percentile), which is typically seen in the exdonor twin. Doppler blood flow studies of theumbilical artery in the growthrestricted fetus are obtained weekly once viability is reached. If abnormal flowresults are present in the umbilical artery (absent or reversed diastolic flow), Doppler flow studies of the

development. (See 'Persistent or recurrent TTTS' below.)

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Beginning at 30 weeks of gestation, biophysical profile scores are obtained weekly

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Delivery is scheduled at 36 to 37 weeks of gestation, in the absence of complications necessitating earlier

delivery. Early delivery is indicated due to the risk of unexplained fetal death at term

MANAGEMENT OF QUINTERO STAGE II TO IV — Intervention for pregnancies at Quintero stage II to IV isindicated because reports suggest a poor prognosis with expectant management alone. Overall perinatal survivalwith Quintero stage II or more was only approximately 30 percent in a literature review of 28 studies involving atotal of 68 pregnancies with untreated TTTS between 1966 and 1991 [19]. By comparison, perinatal survival wasapproximately 60 percent in two large series with therapeutic intervention [20,21]

Choice of therapy at 16 to 26 weeks of gestation — Fetoscopic laser ablation of placental anastomoses is thepreferred procedure for definitive treatment of Quintero stage II to IV TTTS between 16 and 26 weeks of

Following amnioreduction, fetal ultrasound examination is performed weekly to evaluate for complications,progression to more advanced stage of TTTS, and response to therapy. The amniotic fluid and fetal

membranes are assessed to detect signs of membrane separation, inadvertent septostomy, membrane

rupture, unexpected changes in amniotic fluid volume, and evidence of a therapeutic response

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Amnioreduction is repeated if the patient becomes symptomatic (contractions or respiratory compromise)due to uterine overdistention from recurrent polyhydramnios

Fetal growth is assessed every three to four weeks. If selective fetal growth lag is identified (ie, one fetus withestimated fetal weight <10 percentile), Doppler blood flow studies of the umbilical artery in the growth

restricted fetus are obtained weekly. If abnormal flow results are present in the umbilical artery (absent orreversed diastolic flow), Doppler flow studies of the ductus venosus are added to the monitoring paradigm. Iffetal growth discordance is detected and preterm delivery is likely, a course of antenatal glucocorticoids isadministered

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Beginning at 28 weeks, Doppler blood flow studies to assess MCAPSVs are obtained weekly. As discussedabove, discordant values are indicative of TAPS, a milder form of TTTS that occurs spontaneously in 5

percent of monochorionic twins. TAPS is diagnosed when MCAPSV is >1.5 MoM in one fetus in conjunctionwith a value of <1.0 MoM in the other. (See 'Twin anemia polycythemia sequence' below.)

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Beginning at 30 weeks of gestation, biophysical profile scores are obtained weekly

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gestation [22]

Although a 2014 metaanalysis of randomized trials comparing laser ablation with amnioreduction did not find astatistically significant improvement in survival with laser therapy, the two trials had discordant results (Eurofetusreported improved survival with laser ablation [23]; the United States trial did not [20]) and in both trials the laserablation group was more likely to be alive without neurologic complications at six years of age [24]. However,

there were several limitations to these data: <200 pregnancies were studied; approximately 90 percent of

pregnancies in both trials had stage II or III disease, but the proportions of stage I and stage IV disease

randomized were insufficient to answer the question regarding benefit. The Eurofetus trial enrolled patients at allstages of TTTS; of the 142 randomized cases, 11 were stage I (6 randomized to laser and 5 to amnioreduction)and 2 were stage IV cases (1 randomized to laser and 1 to amnioreduction). In the United States trial, stage Icases were excluded; of the 42 randomized cases, 4 were stage IV (3 randomized to laser and 1 to

amnioreduction). Thus pregnancies in the United States trial were at the more severe end of the disease

spectrum. Both trials were stopped early: Eurofetus was stopped early because a planned interim analysis

demonstrated a significant benefit in the laser group. The United States trial was stopped early because referringclinicians were no longer willing to refer patients to the participating centers for randomization after the publication

of the Eurofetus report. The reduced enrollment along with the finding of a statistical trend in adverse outcomes

in recipient twins undergoing laser resulted in the decision to stop the trial

Additional support for the effectiveness of laser therapy was provided by a 2013 metaanalysis of cerebral injuryfollowing laser therapy versus amnioreduction, which included four observational studies involving 357 children inthe amnioreduction group and 269 children in the laser group [25]. Cerebral injury in live born infants in the

amnioreduction group was more than sevenfold higher than in live borns in the laser group (95% CI 2.820). Afterexcluding neonatal deaths from the analysis, infants from pregnancies treated with amnioreduction still had a

marked increase in neurologic injury (relative risk 3.23, 95% CI 1.457.14) compared with the laser group. Thegestational age at the time of intervention was comparable, 20 to 22 weeks; however, the median gestational age

at delivery was lower in the amnioreduction group compared with the laser group, 28 to 31 versus 32 to 34. Theauthors speculated that the increased risk of cerebral injury in the amnioreduction group was due to the higherrate of prematurity

Prenatal followup and care — Prenatal followup and care are identical to that in stage I TTTS patientstreated with laser ablation. (See 'Prenatal followup and care after laser therapy' above.)

Choice of therapy at >26 weeks of gestation — Amnioreduction is the preferred intervention for treatment ofQuintero stage II to IV TTTS at >26 weeks of gestation in the United States. As discussed above, the US Foodand Drug Administration investigational device exemption for fetoscopes limits their use to treatment of TTTS at

16 to 26 weeks of gestation. Practically, laser ablation at more advanced gestational ages would be subject toseveral technical limitations: fetal vernix in the amniotic fluid reduces optimal visualization, placental vessels arelarger in caliber and more difficult to successfully coagulate, and greater in utero distances may not be easily

traversed by current fetoscopes. However, some centers offer laser ablation after 26 weeks of gestation, and

there is increasing evidence that procedures performed at later gestational ages can result in outcomes

comparable with those performed in the traditional 16 to 26 week period [1518]. (See 'Amnioreduction' below.)Prenatal followup and timing of delivery — Prenatal followup and delivery timing are identical to that inStage I TTTS patients treated with amnioreduction. (See 'Prenatal followup and care' above.)

MANAGEMENT OF QUINTERO STAGE V — If one fetus has died, the major concerns for the cotwin are death(10 percent risk) or neurologic impairment (10 to 30 percent risk) due to their shared circulation [22]

Management is the same as in monochorionic twin pregnancies without TTTS. (See "Twin pregnancy: Prenatalissues", section on 'Death of one twin'.)

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In these cases, neither laser therapy nor amnioreduction can prevent cerebral damage in the surviving twin asthe insult occurs at the time of the death of the cotwin. The goal is to optimize the outcome for the surviving cotwin and avoid complications of iatrogenic prematurity. A thorough ultrasound survey of the surviving cotwin

should be performed including Doppler blood flows studies of the middle cerebral artery peak systolic velocity(MCAPSV). Excluding fetal anemia (MCAPSV) in the setting of an acute fetal cotwin demise essentially

eliminates the possibility that major exsanguination occurred and most likely has a favorable prognosis [26]. In thepreterm fetus, expectant observation with serial fetal ultrasound examinations every three to four weeks is

performed to follow fetal growth and central nervous development. Magnetic resonance imaging examinationthree to four weeks following the fetal demise is indicated to detect intracranial damage. Emergent delivery in thepreterm setting does not improve cotwin outcome

In utero transfusion to correct fetal anemia within 24 hours of intrauterine fetal death has been offered at somecenters, but the benefit of this intervention has not been established [27]. We perform in utero transfusion after

an acute demise with fetal anemia documented by MCAPSV

FETOSCOPIC LASER ABLATION OF ANASTOMOTIC VESSELS — Fetoscopic laser ablation is a procedure

in which a laser is inserted through a fetoscope and used to ablate superficial blood vessels on the surface of theplacenta that cross the intertwin membrane. Although anastomoses exist deep in the placenta, their afferent andefferent branches are superficial. Theoretically, coagulation of the superficial vessels should eliminate unbalancedtwintwin transfusion

The procedure is available at several tertiary obstetrical centers in the United States and worldwide. It should only

be performed by clinicians with extensive training and expertise performing the procedure

Patient preparation — Fetoscopic laser coagulation is generally performed as an outpatient procedure underlocal anesthesia with intravenous sedation, although some centers use regional anesthesia. General anesthesiawith endotracheal intubation may be required in select cases when there is respiratory difficulty from extremepolyhydramnios. We administer a firstgeneration cephalosporin within one hour of starting the procedure;

nifedipine 10 mg orally is given just prior to the procedure to suppress uterine contractions. After 24 weeks ofgestation, a course of antenatal corticosteroids is administered in case of preterm delivery. Some centers

administer indomethacin rather than nifedipine. We do not use indomethacin because of reports of an increasedrisk of renal compromise in the donor twin when multiple doses of this agent were used to treat hydramnios in therecipient twin

A thorough obstetrical ultrasound examination is performed, including determination of the distance between thetwo placental umbilical cord insertion sites. If the sites are too close together (defined as <2 cm), the vascularanastomoses can be difficult to visualize and coagulate [28,29] and an alternative intervention or expectant

management may be necessary. However, proximate cord insertions are uncommon, occurring in only 1 to 2

percent of cases of TTTS

Procedure — The suspected intertwin vascular equator is located in the region between the two placental

umbilical cord insertion sites. The lie of the "stuck" donor twin typically parallels this equator. A site for entry intothe recipient sac is selected at 90 degrees to the equator. Power Doppler is used to locate an avascular area inthe uterine wall

The skin is prepped with hexachlorophene and anesthetized with a local anesthetic (we use 0.25 percent

bupivacaine). Percutaneous entry may be via the Seldinger technique or by sharp trocar. For the Seldinger

technique, an 18gauge diamond point needle is inserted followed by insertion of a J wire through the needle andthen removal of the needle. A 9 to 12 French intravenous catheter is then placed percutaneously over the guidewire under ultrasound guidance. Alternatively, a sharp metal trocar can be placed in the cannula and used forentry into the uterus

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A 2 to 3 mm diameter fetoscope is then inserted through the cannula. If the placenta is anterior and centrally

located, entry into the uterus from an extreme lateral approach can result in puncture of the placental edge or thedilated adnexal vascular complex. Specialized fetoscopes with 30 and 70 degree lens have been developed thatallow better visualization of the anterior placenta in these cases. In rare cases where percutaneous access is notpossible due to the adnexal vasculature, a laparoscopicassisted approach can be utilized. This method directsthe fetoscope through the posteriorlateral uterine wall under direct visualization [30]

Visualization of all four distal extremities of both fetuses is attempted. This is especially important in cases of

TTTS complicated by twin anemia polycythemia sequence (TAPS) where the plethoric twin may show signs ofthrombosis of extremities (eg, skin bullae and blanching of the affected limb) [31]

We prefer the equatorial dichorionization (Solomon) technique, which has three components:

Identify the vascular equator and map the anastomoses – The intertwin membrane on the placentalsurface is located as a landmark. The vascular equator is then identified and the types of anastomoses

mapped. The type of anastomosis is determined based on several features as they are visualized throughthe fetoscope

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Arteriovenous (AV) or venoarterial (VA) connections appear as a single vessel originating from the donor orrecipient; this vessel disappears into the placental mass and a second vessel in immediate proximity of thedisappearing vessel can be traced leading back to the cotwin. The arterial component of the anastomosis isdark redblue (deoxygenated blood), while the venous component is bright red (oxygenated blood). If colordifferentiation can be easily discerned, a vessel can be traced back to its origin from the cord insertion intothe placenta. Placental arteries are noted to cross over placental veins

Arterioarterial (AA) anastomoses appear as dark tortuous vessels that connect the twin circulations on thesurface of the placenta. Often, pulsating color changes can be seen by fetoscopy as the blood components

of the two twins oscillate in the vessel

Venovenous (VV) anastomoses are rare. When present, they appear as relatively straight vessels that

course between the two fetal circulations on the placental surface

In most cases, the vascular equator can be located in the recipient sac; however, occasionally it is irregularwith some component located in the donor sac. The uterine wall at either end of the placenta is examinedcarefully to ensure that an eccentric communicating vessel is not coursing outside of the placental mass

Coagulate all visible anastomoses – Laser energy (20 to 40 watts from a diode or YAG laser) is appliedthrough a 400 to 600 micron quartz fiber introduced through an operating channel in the fetoscope. A

second channel allows for continuous irrigation to promote visualization. The anastomotic vessels are thencoagulated in a specific sequential sequence (called sequential selective laser photocoagulation):

Arteriovenous (AV, donor artery to recipient vein), then venousarterial (VA, donor vein to recipient artery),and lastly arterialarterial (AA) and venousvenous (VV) anastomoses. As an example, ablation of an AVanastomosis is shown in the video (movie 1) and in the following series of photographs (picture 1 and picture

2 and picture 3)

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Sequential selective ablation has been associated with a 40 to 50 percent reduction in risk of intrauterinedemise of the donor or recipient twin compared with selective ablation, the older standard technique. Thesequential selective technique requires a specific order of ablation of the type of anastomoses as stated

above, whereas ablations of the anastomoses with the selective technique are done in no specific order

[21,32]. It has also been associated with an almost doubling of the rate of dual perinatal survival. However,these results should be interpreted cautiously because pregnancies that underwent the standard procedure

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Other complications that have been reported in less than 10 percent of cases include recurrent TTTS, amnioticfluid leakage into the maternal peritoneal cavity, vaginal bleeding/abruptio placenta, and intraamniotic infection[36]. Intraperitoneal leaking is selflimited and often causes maternal discomfort, which can be controlled withanalgesics. Vaginal bleeding, abruption and intraamniotic infection are managed according to standard obstetricprotocols. (See "Placental abruption: Management" and "Intraamniotic infection (clinical chorioamnionitis or tripleI)".)

Complications can lead to miscarriage, fetal demise, or preterm delivery

Preterm birth — The average gestational age at delivery after fetoscopic laser surgery is approximately 31 to

33 weeks of gestation [37]. The major risk factors include preterm premature rupture of membranes (PPROM),short cervix, amnioinfusion during the procedure, and increased number of anastomoses [38]. The most commonetiology for preterm birth is spontaneous preterm labor, which occurs in 48 percent of patients, followed by

indicated preterm birth, which occurs in 32 percent, and elective or scheduled deliveries in 20 percent [39]

Preventive measures such as cervical cerclage did not prolong pregnancy or improve survival in a multicentersecondary analysis of a prospective cohort study including 163 patients, 48 percent of whom had cerclage

placement for preoperative cervical length <25 mm [40]. In another smaller retrospective study of 14 patients, thecerclage improved pregnancy duration and perinatal survival for preoperative cervical length <15 mm [41]

Preterm premature rupture of membranes — The most common serious complication of fetoscopic

intervention is PPROM, which occurred within one and three weeks postprocedure in 7 and 17 percent of cases,respectively, in one series [36] and in 39 percent of cases prior to term [42]. PPROM is associated with a twoweek mean reduction in the gestational age at birth [43]. Diagnosis and management are the same as in any

in these studies did so because of technical difficulties that prevented them from receiving the full sequentialselective treatment, potentially biasing the results [21]

Coagulate the vascular equator (equatorial dichorionization) – After coagulation of all visible

anastomoses, a thin line of placental surface at the vascular equator is coagulated. This line extends fromone edge of the placenta to the other and connects the white areas that resulted from coagulation of the

equatorial coagulation was performed [34]. However, equatorial coagulation did not lead to significant

differences in perinatal mortality or severe neonatal morbidity, and neurodevelopment outcomes at two years

of age were similar for both approaches [33,35]

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pregnancy. (See "Preterm premature (prelabor) rupture of membranes" and "Midtrimester preterm prematurerupture of membranes".)

Iatrogenic PPROM has been attributed to a persistent fetal membrane defect at the trocar entry site. Use of asmall operative cannula (9 or 10 French versus 12 French) decreases the risk of PPROM but prevents use oflarge diameter fetoscopes and fetoscopes with angled lenses, which increase the likelihood of successful laserablation [38]

Instillation of platelets, maternal blood, absorbable gelatin, or a collagen plug has been tried to plug the defect,but none of these approaches has been effective [44]

Membrane separation — Membrane separation can usually be seen at the site of trocar entry and is oftenevident on ultrasound by 24 hours after the laser procedure. It can progress on subsequent ultrasound

examinations to completely encircle the uterine cavity, and no therapeutic interventions are available to prevent orcorrect this complication. Membrane separation was reported after 20 percent of fetoscopic laser procedures forTTTS in one large study [45,46]. It is associated with an increased risk of spontaneous and indicated pretermbirth

Rupture of the intertwin membranes — Rupture of the intertwin membranes creating iatrogenic

monoamniotic twins occurs in up to 20 percent of cases following laser therapy [47]. It should be suspected whenthe amniotic fluid in the donor sac normalizes rapidly, within 24 hours of the laser procedure. Complications

include cord entanglement and limb constriction defects, so called pseudoamniotic band syndrome (PABS)

formation resulting in compromise of blood flow to the cord or fetal extremities [48,49]. PABS will also be seen in

1 to 2 percent of recipient twins due to the disruption of the amnion at the fetoscopic insertion site. PABS canresult in constriction defects, which have been limited to the distal extremities and, to our knowledge, have notresulted in amputation or functional limitation of the affected limbs. Prenatal intervention is not indicated for

PABS

We manage these pregnancies similar to naturally occurring monoamniotic twins. (See "Monoamniotic twin

pregnancy".)

Intraamniotic bleeding during the procedure — Intraamniotic bleeding may obscure visualization andthus prevent completion of the procedure. In these cases, amnioinfusion using the rapid infuser pump utilized bytrauma services to provide warmed blood can be very useful to clear the operative field. We have this equipmentavailable and set up at all procedures

Lactated Ringer's solution with 1 g/L of nafcillin is administered (clindamycin 400 mg/L if the patient is penicillinallergic). The remaining portion of the procedure should be completed as rapidly as possible; often a non

selective coagulation method is used (ie, coagulating all vessels along the intertwin membrane). Depending onthe severity of the bleeding coagulation of the vascular equator, the Solomon technique may not be possible

Fetal demise — Procedurerelated fetal loss has been reported in 10 to 30 percent of cases [22]. Risk factorsfor fetal demise include [5053]:

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466 patients from eight North American treatment centers, stepwise logistic regression showed that REDF in theumbilical artery after laser ablation was predictive of fetal death in the donor twin (OR 4.0, 95% CI 1.5410.2),while fetal death in the recipient twin after laser therapy was predicted by hydrops (OR 3.7, 95% CI 1.112.7) and

a reversed "a" wave in the ductus venosus (OR 2.39, 95% CI 1.274.51) [51]. In a smaller study (n = 215

consecutive cases), middle cerebral artery peak systolic velocity (MCAPSV) >1.5 multiples of the median (MoM)was observed in 5 of 139 recipients (3.6 percent) postlaser ablation and was predictive of fetal death (odds offetal death: OR 22, 95% CI 1.8267); two deaths occurred among these five recipients [52]

Twin anemia polycythemia sequence — TAPS is a mild variant of TTTS characterized by a large intertwinhemoglobin difference without amniotic fluid discordance. Postlaser TAPS occurs in 2 to 13 percent of TTTSpregnancies treated with laser ablation up to six weeks after the procedure [54,55]. Risk factors include TTTSwith few anastomoses and no arterytoartery communications before laser ablation [56]. TAPS may also occurspontaneously. The pathogenesis, diagnosis, and classification of TAPS are reviewed separately. (See "Twintwintransfusion syndrome and twin anemia polycythemia sequence: Pathogenesis and diagnosis", section on 'Twinanemia polycythemia sequence'.)

Persistent or recurrent TTTS — A 2012 systematic review reported the incidence of recurrent TTTS rangedfrom 0 to 16 percent [60]. Residual anastomoses can lead to persistent or recurrent TTTS. They may have beenmissed at the time of laser ablation or revascularized after the procedure. Measures for reducing the risk of

residual anastomoses include more careful scrutiny of the placental margins (where the majority of residual

anastomoses have been found) and use of the Solomon technique. (See 'Procedure' above.)

Persistent or recurrent TTTS can be managed with expectant management, repeat fetoscopic laser ablation, oramnioreduction, depending on the Quintero stage and gestational age

Treatment – Consideration for treatment is based on progression of the discordance between the MCAPSVs of the twins. We reserve treatment for pregnancies with stage II TAPS (ie, MCAPSV of >1.7 MoM inone fetus and <0.8 MoM in the other fetus). TAPS after laser ablation has been treated with repeat lasertherapy, in utero fetal transfusion [57], selective feticide, expectant management, and early delivery. The

optimal treatment has not been determined and should be decided on a casebycase basis [54,57,58]. Thedecision of the best approach is based on gestational age and the acuity of the TAPS. If there is a significantdisparity in the MCA velocities of the twins soon after the procedure, we offer selective reduction or an

patients are delivered at 32 weeks of gestation, in the absence of complications necessitating earlier delivery.Neurodevelopmental outcome – The only study that specifically evaluated longterm neurodevelopmentaloutcome of fetuses who developed TAPS after fetoscopic laser ablation for TTTS reported mild to moderatecognitive delay (score <85) in 8 of 47 children (17 percent) and severe cognitive delay (score <70) in 2 of 47children (4 percent) assessed at 24 to 96 months of age [59]. Overall, severe neurodevelopmental

impairment occurred in 4 of 47 children (9 percent): cerebral palsy (n = 1), severe motor delay (n = 1),

severe cognitive delay (n = 2); these four children were delivered at 28, 29, 29, and 32 weeks of age, whichmay account for at least some of these impairments. The small sample size and variety of tests used for

neurodevelopmental evaluation limit interpretation of these findings

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Reverse TTTS — Reverse TTTS is a rare occurrence postlaser in which each twin assumes the former

phenotype of the cotwin (eg, the former donor develops hydramnios and the former recipient develops

oligohydramnios). It is unclear how the apparent reversal of the transfusional gradient occurs, but when present,the outcomes are compromised with overall survival rates <50 percent [61,62]

Outcome

Perinatal survival — In a literature review, overall perinatal survival after laser therapy of stage I to IV TTTSwas 65 percent (1306/2016) [22]. Approximately onethird of pregnancies had one survivor and onehalf had twosurvivors. Survival is higher with stage I and II disease and lower with stage III and IV disease

Neurodevelopmental impairment — In a 2011 systematic review of studies evaluating neurodevelopmentaloutcome in pregnancies complicated by TTTS and treated with laser [63]:

The overall risk of neurologic impairment postlaser therapy is not significantly different from the baseline risk inmonochorionic twins without TTTS or in dichorionic twins matched for gestational age at delivery [6466]. Almostall of the risk of neurologic impairment in survivors is due to prematurity and prematurityrelated complications,rather than a direct result of TTTS or laser therapy [63,6668]

Renal effects — Chronic hypovolemia in the donor may result in vascular remodeling [69], which may be

prevented by laser ablation [70]. In the only study of the longterm renal effects of TTTS treated with laser, nosignificant differences in serum and urinary markers of renal function were noted in 18 surviving twin pairs

followed to a median age of three years [71]

Cardiovascular effects — Fetoscopic laser photocoagulation usually improves cardiovascular function inboth twins. Optimal initiation of this therapy has shortened disease duration compared with past decades, whichappears to provide time for cardiac remodeling before delivery [72]. However, pulmonary valve pathology maypersist and require postnatal intervention [73]. One series of 51 recipient survivors of laser therapy observed that

8 percent had pulmonary stenosis at the time of birth, a 200fold increase over the rate in the general population[74]. Onehalf of the cases required valvular balloon dilation for treatment. Nevertheless, when assessed at amean age of 10 years, childhood cardiac function was normal in the majority of surviving donors and recipients[75]

AMNIOREDUCTION — Amnioreduction reduces uterine overdistention, which is a risk factor for preterm laborand preterm premature rupture of membranes (PPROM). It also decreases pressure inside the amniotic cavityand may thus improve uteroplacental perfusion [76,77]

Procedure — A variety of amnioreduction techniques have been described; no randomized trials have evaluatedwhether one is safer and more effective than another. There is no consensus regarding how much fluid to

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Cerebral palsy accounted for 39.7 percent (60/151) of longterm abnormal neurologic outcomes

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avoiding the placental edge, if possible. The placenta will be markedly thinned on ultrasound imaging because ofthe excessive amniotic fluid

The needle is placed as close to the midline of the uterus as possible with a slight angulation toward the maternalxiphoid to reduce the risk of needle displacement as the uterine size diminishes with drainage of amniotic fluid.The needle can be connected to one end of the specialized tubing included in a disposable thoracocentesis tray(male to male ends) while the other end of the tubing is connected to a short 18gauge needle that is spiked into

a disposable vacuum bottle. This setup maintains a closed system, avoids excessive needle manipulation, andallows the rate of flow to be controlled with the rollerball valve in the line

Some authors recommend removing fluid until polyhydramnios is no longer present (maximum vertical pocket <8cm); others suggest removing no more than 5 liters of amniotic fluid over approximately an hour [78]

Decompression of the uterus with rapid removal of a large volume of fluid may cause placental abruption or fetalbradycardia; therefore, we suggest removing no more than 3 liters of fluid in severe TTTS

Outcome — The International Amnioreduction Registry reported outcomes from the largest series of TTTS

patients undergoing amnioreduction [79]. A total of 223 twin pregnancies from 20 fetal medicine units were

diagnosed with TTTS prior to 28 weeks of gestation and treated with 760 amnioreductions. The major findingsfrom this series were:

SELECTION REDUCTION — Selective reduction of one twin is an option that may improve the prognosis of thecotwin if a technique is used that does not impact its circulation. While perinatal outcomes are comparable

amongst the various procedures (bipolar cord coagulation, laser cord coagulation, and radiofrequency ablation[RFA]), RFA is our preferred technique for selective reduction of monochorionic twins because the smaller devicereduces maternal morbidity [80]

The fetus predicted to have the least chance for survival is usually selected for the reduction procedure. The

available data do not show a difference in survival according to whether the donor or recipient twin is targeted[81]. If bipolar cautery is used, reduction of the recipient twin is technically easier since its cord is easily visualizedfloating amid the excess amniotic fluid. Oligohydramnios around the donor makes this twin a more difficult target,although the donor cord can be grasped through the intertwin membrane after entry into the recipient's amnioticcavity. This can result in a septostomy and the risk of subsequent cord entanglement. However, if the donor twin

is the primary target, amnioinfusion can be performed to improve access for the bipolar forceps. Radiofrequencyablation does not require amnioinfusion [82]

Experience with selective reduction for TTTS is limited. One study including 15 cases of TTTS treated with

bipolar coagulation of the umbilical cord reported an overall survival of 87 percent in the cotwin, but preterm

premature rupture of membranes occurred in 20 percent of pregnancies within three weeks of the procedure [83].Another study including 22 cases of TTTS treated with bipolar cautery reported an overall survival of 77 percent[84]. One infant had developmental delay at 16 months of age. In a third series of 24 cases of TTTS, the overall

Complications associated with the procedure included PPROM within 48 hours of the procedure (6

percent), spontaneous delivery (3 percent), fetal distress (2 percent), fetal death (2 percent), placentalabruption (1.3 percent), and chorioamnionitis (1 percent)

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Both twins were live born in 55 percent of pregnancies, one twin was live born in 31 percent, and bothtwins were stillborn in the remaining 14 percent. During the first four weeks of neonatal life, an additional

30 percent of liveborn twins succumbed

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Intracranial abnormalities were observed on neonatal cranial ultrasound in 24 percent of recipient twinsand 25 percent of donor twins that survived to four weeks of age

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