**3.4. Twin reversed arterial perfusion sequence**

positive predictive value, and a 99% negative predictive value [115]. In some TAPS cases, other ultrasound findings have been reported. The first one is the difference in placental thickness, and echodensity on ultrasound examination was detected [110]. Another ultrasound finding described in TAPS is the so-called starry sky liver [116] which is characterized by clearly identified portal venules and diminished parenchymal echogenicity. More studies are needed to further investigate the validity and significance of these antenatal ultrasound

The postnatal criteria (**Table 2**) can be used when TAPS is not diagnosed by MCA Doppler. It is based on the finding of discordant hemoglobin levels (Hb difference > 8.0 g/dl) associated with an increased intertwin reticulocyte count ratio > 1.7 that is pathognomonic for TAPS and

The classification for TAPS was proposed by Slaghekke et al. in 2010 [111] based on the differ-

There is no optimal treatment for TAPS. Options include expectant management and early delivery; intrauterine transfusion (IUT) in the donor, with or without partial exchange trans-

Expectant management is made with closing ultrasound monitoring with serial MCA-PVS evaluation and an early delivery when necessary. It leads to a 75 to 83% survival rate [111, 118]. Another kind of treatment is IUT that can be performed intravascularly or intraperitoneal. It seems the latter may be superior to intravascular intrauterine transfusions because it is technically easier and can be performed as early as 15 weeks [119]. Although this method is commonly used, it is a palliative option, since it temporarily meliorates the donor anemia. Furthermore, the raise in blood viscosity in the recipient twin can lead to embolic complications [67]. These complications can be managed by partial exchange transfusion (PET) that decreases the viscosity of the blood of the polycythemic recipient. The perinatal survival rate

fusion (PET) in the recipient; selective feticide; and fetoscopic laser surgery.

placental evidence of only small vascular anastomoses [111, 117].

in some studies is generally good, reaching 85–100% [111, 118].

Stage V Intrauterine demise of one or both fetuses preceded by TAPS

umbilical vein, and increased pulsatility index or reversed flow in ductus venosus.

signs of fetal compromise

signs of fetal compromise

Stage I MCA-PSV donor >1.5 MoM and MCA-PSV recipient <1.0 MoM, without other

Stage II MCA-PSV donor >1.7 MoM and MCA-PSV recipient <0.8 MoM, without other

Stage III As stage I or II, with cardiac compromise of donor, defined as critically abnormal flow\*

**Table 3.** Antenatal TAPS classification. Adapted from Ultrasound Obstet Gynecol. Slaghekke et al. [111].

\*Critically abnormal Doppler is defined as absent or reversed end-diastolic flow in umbilical artery, pulsatile flow in the

ence in hemoglobin levels postnatally (**Table 3**).

findings for the diagnosis of TAPS.

140 Multiple Pregnancy - New Challenges

*3.3.2. Management of TAPS*

**Antenatal stage Doppler ultrasound**

Stage IV Hydrops of donor

Twin reversed arterial perfusion sequence resulting in an acardiac twin is a rare condition and occurs in 1:35,000 births or 1% of all monozygotic twins [122]. It consists in one health twin (the "pump" twin) and one acardiac mass which is perfused by the other fetus' heart. This acardiac twin most often has an underdeveloped head and upper body and impressive edema also mostly of the upper body. In some cases, there might be fetal movements. In rare cases, a rudimentary pulsating cardiac structure may be seen. It is though that the VV and AA bidirectional anastomoses are responsible for the perfusion of the acardiac fetus. One study analyzed the TRAPS placenta and found big AA anastomoses as well as veins in direct continuity with each other. They also noted that umbilical cords were attached, with insertion adjacent to each other [123]. The blood from the pump twin flows through the umbilical artery to the umbilical artery of the acardiac twin and then it flows back to the recipient twin through the umbilical vein. The returning blood bypasses the placenta and returns to the pump twin via VV anastomoses, without passing through the placenta. This condition may cause a hyperdynamic circulation and progressive high output cardiac failure in the pump twin causing fetal death in about half of cases if not treated [122, 124, 125].

The diagnostic is made by turning on the color Doppler and showing the inverse direction of blood flow in the aorta of the acardiac twin [92] (**Figure 11**). TRAPS is usually diagnosed in the 11–13 weeks scan or even in the early endovaginal ultrasound [126–128]. Given the fact that 50% of pump twin dies if expectant management is made and that in 33% of the TRAPS pregnancies diagnosed at the first trimester the healthy twin dies before 18 weeks [123, 129], several intrauterine interventions have been tested in order to improve the perinatal outcomes. The overall survival of the treatment methods is similar among several studies and varies between 71 and 86% [130–134]. The methods used to manage TRAPS are cord ligation; monopolar, bipolar, or laser cord coagulation; and fetoscopic laser coagulation of placental anastomoses. However, intrafetal techniques such as intrafetal laser ablation and intrafetal radiofrequency ablation (RFA) are preferred because, when compared to cord occlusion

**4. Conclusion**

ablative techniques.

**Conflict of interest**

**Author details**

**References**

Bruno Rodrigues Toneto

There are no conflicts of interest in this chapter.

Address all correspondence to: brunotoneto@yahoo.com.br

Federal University of São Paulo, São Paulo, Brazil

Hill Education; 2014. pp. 891-924

Monochorionic pregnancies are at a great risk of complications such as preterm birth, fetal and neonatal death, and neurological injury. The early sonographic screening is extremely important to diagnose some of the most important complications which can lead to death of one or both siblings. It should begin in the first trimester, where the confirmation of chorionicity should be done and the search for potential predictors of adverse outcomes such as NT discordance should be accessed. Some complications such as TRAPS can be diagnosed and managed in this period. Beginning in the 16th week, a biweekly detailed ultrasound examination is extremely important since it can detect early stages of TTTS, sFGR, and TAPS. Most of these complications

Complications in Monochorionic Pregnancies http://dx.doi.org/10.5772/intechopen.83390 143

can be treated in the mid-trimester improving the survival rate of one or both fetuses.

The fetoscopic approach is the main method to manage MC twin complications and should be available in specialized fetal medicine centers with trained staff to perform the laser surgery. Several laser techniques have been tested in the last years and the improvement in the outcomes is clear. Although the results are satisfactory, the complication rates, such as PROM and unintentional septostomy, are still relatively high as well as the both twins' survival rate. Future directions in the management of TTTS are likely to involve refinements in the prediction of the disease, clarification of the optimum frequency of surveillance, technique of laser therapy, prediction of adverse outcome after treatment, and development of other vascular

Although the treatment efficacy is rapidly improving in big centers, in most parts of the world, there is a lack of specialized centers and trained personnel. In order to achieve an optimal management in MC pregnancy complications, it is important to improve the early

[1] Gary Cunningham F. Multifetal pregnancy. In: Williams Obstetrics. 24th ed. McGraw-

screening and diagnosis and the referral system, mainly in low-income countries.

**Figure 11.** Upper image: Acardiac twin with retrograde flow in the umbilical cord. Lower image: Normal recipient twin. Adapted from ultrasound Obstet Gynecol. Pagani et al. [124].

techniques, they are associated with a lower technical failure rate (13 vs. 35%), lower rate of preterm birth or rupture of membranes before 32 weeks (23 vs. 58%), and higher rate of clinical success (77 vs. 50%) [135].

There are some doubts about the optimal time to do the treatment. Performing any procedure before the obliteration of the coelomic cavity increases the risk of talipes and miscarriage [136]; therefore, most of the authors perform the intervention between 13 and 16 weeks [124]. In one study in which the median gestational age at intervention (intrafetal laser ablation) was 13.2 weeks, there was a 41% mortality rate in the first 72 h after the procedure; therefore, surgery before 13 weeks of gestation should be avoided [136]. Some studies showed that expectant management could be offered in special cases. Jelin et al. [125] found a 100% survival when the acardiac twin had less than 50% of the pump twin's weight. Other studies suggested that discordance between crown-rump length of the pump twin and upper pole-rump length of the TRAP twin could be potential predictors of pregnancy outcome [137].

The optimal approach should be an early diagnosis and a proper parental counseling and an intrafetal intervention, by laser or RFA in 13–16 weeks. The expectant management could be considered if the TRAP twin is smaller (about half the size) than the pump twin.
