lable at ScienceDirect

Placenta 31 (2010) 163–165

Contents lists avai

Placenta

journal homepage: www.elsevier .com/locate/placenta

Case report

Arterio-Arterial Anastomoses do not Prevent the Development of TwinAnemia-Polycythemia Sequence

H. van Meir a,*, F. Slaghekke b, E. Lopriore c, W.J. van Wijngaarden a

a Division of Gynecology and Obstetrics, Bronovo Hospital, Bronovolaan 5, 2597 AX Den Haag, The Hague, The Netherlandsb Division of Gynecology and Obstetrics, Leiden University Medical Center, Leiden, The Netherlandsc Division of Neonatology, Leiden University Medical Center, Leiden, The Netherlands

a r t i c l e i n f o

Article history:Accepted 19 November 2009

Keywords:Twin anemia-polycythemia sequencePlacental angioarchitectureArterio-arterial anastomosis

* Corresponding author. Tel.: þ31 70 3124141.E-mail address: helenevanmeir@hotmail.com (H. v

0143-4004/$ – see front matter � 2009 Elsevier Ltd.doi:10.1016/j.placenta.2009.11.009

a b s t r a c t

Monochorionic twin pregnancies are associated with increased perinatal morbidity and mortality. Thevascular placental anastomoses in these pregnancies can cause severe complications.

We describe a case of twin anemia-polycythemia sequence (TAPS) with an atypical placentalangioarchitecture. During pregnancy serial ultrasound examinations of both twins revealed no amnioticfluid discordance and no abnormal Doppler ultrasound measurements (umbilical cord pulsatility indexand middle cerebral artery peak systolic velocity). The twins, born at 33 þ 3 weeks gestation afterspontaneous onset of labour, were found to be anemic and polycythemic, respectively. Placentalexamination with colored dye injection showed, apart from small ateriovenous anastomoses, an arterio-arterial anastomosis. As arterio-arterial anastomoses have not been described in cases with spontaneousTAPS to date, it was postulated that such anastomoses carried a protective effect against the developmentof this complication.

� 2009 Elsevier Ltd. All rights reserved.

1. Introduction

Placental vascular anastomoses in monochorionic twin gesta-tions may lead to twin-to-twin transfusion syndrome (TTTS).Recently, a variant of TTTS was described: twin anemia-poly-cythemia sequence (TAPS) [1–3]. TAPS is characterized by thepresence of a large inter-twin difference in haemoglobin level andreticulocyte count without any signs of the oligo-polyhydramiossequence as seen in TTTS. TAPS may occur spontaneously (spon-taneous form) or after laser surgery in the treatment of TTTS (post-laser form). The spontaneous form of TAPS occurs in approximately3%–5% of monochorionic twin pregnancies [3,4], whereas the post-laser form of TAPS may occur in up to 13% of TTTS cases treated withlaser [5].

TAPS may be suspected antenatally based on abnormal Dopplerultrasound findings in the absence of amniotic fluid discordance.Abnormal Doppler findings in TAPS consist of an increased middlecerebral artery peak systolic velocity (MCA-PSV) suggesting anemiain one fetus, with a simultaneous decrease in the MCA-PSV in theco-twin suggesting polycythemia [3–5]. Postnatal diagnosis of TAPS

an Meir).

All rights reserved.

is based on the presence of chronic anemia (with reticulocytosis) inthe donor and polycythemia in the recipient twin.

The pathophysiological mechanism leading to TAPS is not clear.We recently studied the placental angioarchitecture of a smallgroup (N ¼ 11) of monochorionic placentas with TAPS andcompared those with a control group of monochorionic placentasfrom uncomplicated twin pregnancies [4]. We found that TAPSplacentas were characterized by the presence of only few and thinarterio-venous (AV) anastomoses, in the absence of arterio-arterial(AA) anastomoses [4], and speculated on the hypothetical linkbetween this particular angioarchitecture and the development ofTAPS.

We now describe a spontaneous case of TAPS with an atypicalplacental angioarchitecture.

2. Case presentation

A healthy 30-year-old gravida 3 para 0 was referred to ourhospital at 12 weeks’ gestation with a spontaneous monochorionic-diamniotic twin pregnancy. The course of the pregnancy wasuneventful and serial fetal ultrasound examinations performedevery two weeks showed no signs of a twin oligo-polyhydramiossequence. The umbilical artery pulsatile index (PI) was neverabnormal in either twin. Until 30 weeks’ gestation, Dopplermeasurements of the MCA-PSV showed no abnormalities and both

Fig. 1. On top: maternal surface of the placenta showing the placental sharingdiscordance and the difference in color between the pale placental share of the donor(right side) and the congested placental share of the recipient (left side). Below:Placenta after dye injection (blue or green for arteries and orange for veins). The whitearrow indicates the small AA anastomosis. The white stars indicate the small AVanastomoses from donor (right side) to recipient (left side). The blue stars indicate thesmall AV anastomoses from recipient to donor.

H. van Meir et al. / Placenta 31 (2010) 163–165164

twins had a normal growth along their individual percentiles. At32 þ 5 weeks’ gestation, the last ultrasound examination beforedelivery (at 33þ 3 weeks) was performed. Due to deep engagementof the fetal head the MCA-PSV of the first twin could not bemeasured accurately during the last two weeks before delivery.

At 33 þ 3 weeks gestation, preterm uterine contractions startedspontaneously and treatment with atosiban and corticosteroidswas initiated. There were no signs of a twin oligo-polyhydramiossequence on ultrasound. Analysis of antepartum cardiotocographyshowed no signs of fetal distress in both fetuses. Spontaneousrupture of the membranes occurred a few hours after admissionand was rapidly followed by a normal vaginal delivery of two girlsboth in cephalic position. The first twin was pale and weighed1810 g (50th percentile). The second was plethoric and weighed2355 g (80th percentile). The Apgar scores were 8/9/10 and 8/10/10respectively and the fetal umbilical cord pH was normal for bothgirls.

The hemoglobin levels at birth were 11.8 g/dL in twin 1 and22.6 g/dL (normal range 14–20 g/dL) in twin 2. The hematocritvalue of the second twin was 67%. The reticulocyte count was 10.6%in twin 1 and 3.8% in twin 2 (normal range: 2–6%). Twin 1 showedno signs of hemodynamic compromise and did not require a redblood cell transfusion. The polycythemic infant had no clinicalsymptoms associated with hyperviscosity and did not requirea partial exchange transfusion. The neonatal hematological differ-ences found at birth (anemia with reticulocytosis in one andpolycythemia in the other twin) were diagnostic of chronic inter-twin transfusion as seen in TAPS. TTTS was excluded given theabsence of twin oligo-polyhydramnios sequence. Acute peripartumtransfusion was deemed unlikely as there were no signs ofhemorrhagic hypovolemic shock in the donor and the presence ofreticulocysis was suggestive of a chronic event. Cranial ultrasoundexamination of both twins showed no abnormalities and furtherneonatal course was uneventful.

Macroscopic placental examination confirmed a mono-chorionic-diamniotic placenta. The placental share of the donorand recipient twin was estimated 58% and 42%, respectively (Fig. 1).Colored dye injection of the placental vessels showed 3 small AVanastomoses (diameters from 0.3 to 0.4 mm) from donor torecipient and 2 small AV anastomoses from recipient to donor(diameter 0.3–0.4 mm) (Figs. 1 and 2). A small AA anastomosis(diameter 0.8 mm) was also detected (Figs. 1 and 2). The diametersof the anastomoses and the placental share discordance weremeasured on the digital picture of the placenta using Image Tool forWindows version 3.0 (Image Tool, San Antonio, TX, USA). Details onthe technique used for placental injection and for the measurementof the placental territory and diameter of the vascular anastomoseshave been described previously [6].

3. Comment

We present a monochorionic-diamniotic twin pregnancy,complicated by a spontaneous form of TAPS with an atypicalplacental angioarchitecture. Placental injection study showed theatypical presence of an AA anastomosis.

AA anastomoses are bi-directional anastomoses and are oftenreferred to as ‘‘superficial’’ anastomoses since they lie on the cho-rionic plate. Various studies have demonstrated that AA anasto-moses occur more frequently in uncomplicated monochorionicplacentas than in TTTS placentas, respectively 80% versus 25% [7,8].AA anastomoses are thus thought to exert a relative protectionagainst the development of TTTS by compensating for the circula-tory imbalance caused by the unidirectional AV anastomoses. Thisprotective role of AA anastomoses which was already proposed by

Schartz in the 19th century [9], has recently also been demon-strated in a mathematical computer model of TTTS [10].

In a recent study on the placental angioarchitecture of 11 indi-vidual cases of spontaneous TAPS, we found only small AV anas-tomoses (diameter< 1 mm), and no superficial AA anastomoses [4].The AV anastomoses in the 11 TAPS cases were from donor torecipient (AV anastomosis) and from recipient to the donor (VAanastomosis). In analogy with the protective role of AA anasto-moses against the development of TTTS, we suggested a linkbetween the development of TAPS and the absence of AA anasto-moses [4]. We postulated that this particular angioarchitecturewould lead to a slow inter-twin blood transfusion, allowing suffi-cient time for hemodynamic compensatory mechanisms to takeplace, thus avoiding the development of a twin oligo-poly-hydramnios sequence [2].

In a recent report, we described a post-laser case of TAPS inwhich a residual AA anastomosis was also detected [1]. Thecurrent case is the first described case of spontaneous TAPS in thepresence of an AA anastomosis. In analogy with the developmentof TTTS, the presence of an AA does not always prevent TAPS to

Fig. 2. On top: details of the small AV anastomoses from donor to the recipient (whitestars) and from recipient to the donor (blue stars). Below: details of the aterio-arterialanastomosis (white arrow).

H. van Meir et al. / Placenta 31 (2010) 163–165 165

develop. Although AA anastomoses appear to be rare in TAPS, theabsence of an AA should not be considered as a diagnosticcriterion for TAPS. However, the relatively rare occurrence of AAanastomoses in TAPS does not necessarily contradict the postu-lated pathophysiology of the underlying mechanism. One couldargue that under certain sustained physiological circumstancesthe net blood flow over the AA anastomosis is nil or minimal,allowing the other AV anastomoses to lead to imbalanced blood

transfusion between donor and recipient twins. Nevertheless, inmost cases these physiological circumstances are probably notsustained and a net blood flow over the AA anastomosis doesensue, thus protecting against the development of TAPS, or forthat matter, TTTS.

In contrast with the previously reported case [1], filling of theAA anastomosis with colored dye in the current case occurredeasily without increased injection pressure or forced manualcompression of the colored dye, suggesting that the AA anasto-mosis was also patent in utero. Interestingly, the diameter of the AAanastomosis in both cases was very small (<1 mm). We hypothe-size that the small size of the AA anastomoses in these 2 cases mayhave played a role in the development of TAPS by preventingadequate inter-twin blood volume equilibration.

In conclusion, we describe a new case of a TAPS with an AAanastomosis, showing that the absence of AA anastomoses is nota conditio sine qua non for the development of TAPS. This casereport emphasizes the extreme complexity of the pathophysio-logical mechanisms responsible for the complications seen inmonochorionic twin pregnancies and the work that still needs to bedone to understand these mechanisms.

References

[1] Lopriore E, van den Wijngaard JP, Middeldorp JM, Oepkes D, Walther FJ, vanGemert MJ, et al. Assessment of feto-fetal transfusion flow through placentalarterio-venous anastomoses in a unique case of twin-to-twin transfusionsyndrome. Placenta 2007;28:209–11.

[2] Lopriore E, Middeldorp JM, Oepkes D, Kanhai HH, Walther FJ,Vandenbussche FP. Twin anemia-polycysthemia sequence in two mono-chorionic twin pairs without oligo-polyhydramnios sequence. Placenta 2007;28:47–51.

[3] Lopriore E, Oepkes D. Fetal and neonatal haematological complications inmonochorionic twins. Semin Fetal Neonatal Med 2008;13:231–8.

[4] Lopriore E, Deprest J, Slaghekke F, Oepkes D, Middeldorp JM,Vandenbussche FP, et al. Placental characteristics in monochorionic twins withand without twin anemia-polycythemia sequence. Obstet Gynecol 2008;112:753–8.

[5] Robyr R, Lewi L, Salomon LJ, Yamamoto M, Bernard JP, Deprest J, et al. Prev-alence and management of the late fetal complications following successfulselective laser coagulation of chorionic plate anastomoses in twin-to-twintransfusion syndrome. Am J Obstet Gynecol 2006;194:790–5.

[6] Lopriore E, Sueters M, Middeldorp JM, Oepkes D, Walther FJ,Vandenbussche FP. Velamentous cord insertion and unequal placental terri-tories in monochorionic twins with and without twin-to-twin transfusionsyndrome. Am J Obstet Gynecol 2007;196(2):159.

[7] Umur A, van Gemert MJ, Nikkels PG. Monoamniotic versus diamniotic-mon-ochorionic twin placentas: anastomoses and twin-twin transfusion syndrome.Am J Obstet Gynecol 2003;189(5):1325–9.

[8] Bajoria R, Wigglesworth J, Fisk NM. Angioarchitecture of monochorionicplacentas in relation to the twin-twin transfusion syndrome. Am J ObstetGynecol 1995;172(3):856–63.

[9] Schatz F. Eine besondere Art von einsietiger Polyhydramnie mit andersietigerOligohydramnie bei eineiige Zwillingen. Arch Gynaecol 1882;19:329–69.

[10] Umur A, van Gemert MJ, Nikkels PG, Ross MG. Monochorionic twins and twin-twin transfusion syndrome: the protective role of arterio-arterial anasto-moses. Placenta 2002;23(2–3):201–9.