c-obs 42 management of monochorionic twins new mar 11

7/30/2019 C-Obs 42 Management of Monochorionic Twins New Mar 11

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1 RANZCOG College Statement: C-Obs 42

C-Obs 42

Management of Monochorionic Twin Pregnancy

Monochorionic twins are monozygotic; that is, they arise from one fertilised ovum andcommonly have a shared placenta with vascular anastomoses between the two fetalcirculations. Monochorionic twins are usually diamniotic, with each twin in a separate amnioticsac. Rarely, the twins may be in a single sac (monoamniotic) or even conjoined. Theseconfigurations depend upon the stage of development at which the inner cell mass divided.

Specific complications of Monochorionic Twin Pregnancies

Monochorionic twin pregnancies exhibit the increased complication rates characteristic of (themore common) dichorionic twin pregnancies (such as risk of preterm birth, and increasedmaternal risks), but are also at higher risk of a number of specific monochorioniccomplications. These include:

Twin to twin transfusion syndrome (TTTS) which will occur in approximately 15% ofMonochorionic diamniotic (MCDA) twin pregnancies; and

Selective intrauterine growth restriction (IUGR), commonly due to unequal placentalsharing and velamentous cord insertion;

Death of one twin (see below); Twin reversed arterial perfusion (TRAP) sequence.

All of these conditions contribute to an overall higher perinatal mortality when compared todichorionic twins.1

Determining Chorionici ty in Multiple Pregnancy

Chorionicity is a critical consideration in the management of twin pregnancies and should bedetermined by ultrasound and documented in all twin pregnancies during the first trimester.2Chorionicity is more difficult to determine accurately after 14 weeks gestation. Discordantgender confirms dizygosity with great certainty.

Management of Monochorionic Gestations

Women should be informed about the implications of a monochorionic pregnancy in earlypregnancy, so that the parents can fully discuss options for managing the pregnancy, and plantheir future pregnancy care. In particular, they need to know the importance of notifying theirobstetric care provider of acute increasing abdominal girth or breathlessness, as these may besigns of polyhydramnios and TTTS.

Screening tests for aneuploidy have a lower detection rate than in singleton pregnancies andin some centres nuchal translucency alone will be used without the addition of biochemistry.

NEW College StatementC-Obs 42

1st Endorsed: March 2011Current: March 2011Review: March 2014

The RoyalAustralian and NewZealand College ofObstetricians andGynaecologists


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Surveillance for TTTS

Ultrasound signs such as discordant nuchal translucency or discordant crown-rump length(CRL) in the first trimester increase the likelihood of a later diagnosis of TTTS or IUGR but arenot diagnostic, and have insufficient predictive value to be used as screening tests. Thesecomplications still occur in the presence of reassuring early scans.

Frequent ultrasound surveillance of monochorionic twins is recommended; early recognition of

TTTS will facilitate referral to a tertiary centre for consideration of intervention in a timelymanner. Recommended scanning schedules vary; RCOG recommends 2-3 weekly scanningfrom 16 weeks gestation,8 and two-weekly ultrasound surveillance has been shown to reducethe incidence of late stage TTTS at diagnosis;9 earlier stage diagnosis and earlier interventionis likely to improve outcomes.

For this reason, it is suggested that all women with monochorionic pregnancies should ideallybe offered ultrasound surveillance for TTTS and IUGR every 2-3 weeks following their nuchaltranslucency scan, and 2 weekly from 18 weeks gestation. Ultrasound should be undertakenby a centre with sufficient experience to recognise these complications and refer appropriatelyif they occur. Outcomes with TTTS are optimised where there is timely diagnosis and referralto a tertiary centre for consideration of surgical therapy.

TTTS may take 2 forms:

1. TOPS (twin Oligohydramnios/ polyhydramnios sequence), affecting approximately 10%of monochorionic twins, most commonly seen in the midtrimester. This is recognisedas classical TTTS, with oligohydramnios, poor growth and abnormal umbilical arterydopplers in the donor, and polyhydramnios progressing to cardiac dysfunction andfailure in the recipient.

2. TAPS (twin anemia/ polycythemia sequence) affecting approximately 5% ofMonochorionic twins, and 10% of twins that have undergone laser therapy for TOPS.

TAPS results in very slow transfusion (5-15ml/ 24 hours) from donor to recipient, so isnot characterised by extreme amniotic fluid discordance and cardiac dysfunction, butby significantly discordant middle cerebral artery (MCA) peak systolic velocities,reflecting anemia and polycythemia in the donor and recipient, respectively. It is morecommon in later pregnancy, and is often recognised as neonatal TTTS when verydiscordant haemoglobin levels are recognised at birth. Nevertheless, TAPS can alsobe associated with significant fetal anemia and in utero compromise requiringtreatment. For this reason, ultrasound examination in MC twins should include growth,amniotic fluid volume in each sac, bladder volume, umbilical artery and, preferably,middle cerebral artery Doppler wave forms (after 24 weeks).6,7

Management of Twin-Twin Transfusion Syndrome (TTTS)

TTTS should be managed in a tertiary centre. Laser ablation of vascular connections is therecommended treatment for the majority of pregnancies with TTTS that require intervention,and referral to a laser surgery facility should be considered - even where this would meaninterstate transfer.3 Early referral is recommended to allow optimal treatment before the onsetof severe disease and cervical shortening. Amnio-reduction prior to laser surgery may lead toincreased membrane separation and more difficult laser treatment. Mild TTTS mayoccasionally be managed expectantly or by amnio-reduction and some severe cases may bemanaged by cord ligation of one twin.4 Ongoing surveillance post laser for TAPS (see above)is necessary post laser ablation.

Death of one of a Monochorionic Twin pair

Death of one twin in a monochorionic pair may result in death or neurological disability in thesurvivor. These events occur around the time of the fetal death, postulated due to agonal


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hypotension as the blood volume of the survivor is dumped precipitously into the corpse ofthe co-twin through shared vascular communications, or possibly due to the release ofthromboplastins from the deceased twin into the shared circulation. One of the advantages oflaser therapy (or cord ligation) in TTTS is that it provides some neuroprotection for thesurviving twin in the event of co-twin demise. Delivery of the survivor at a preterm gestationwill not prevent further damage unless there is evidence of cardiotocography (CTG)abnormalities or significant fetal anaemia. Ongoing ultrasound or MRI assessment of the brainin the survivor to diagnose neurological damage secondary to hypovolaemia may be

appropriate.

Gestation at Birth

Monochorionic twins, without IUGR or TTTS, appear to have a higher stillbirth rate than othertwin pregnancies despite intensive surveillance.5 This has led to the recommendation thatthese pregnancies should be delivered by 37 weeks gestation. The mode of delivery formonochorionic twins remains controversial. These pregnancies are at risk of intrapartum twinto twin transfusion and should be delivered vaginally only where appropriate facilities exist forcontinuous intrapartum fetal surveillance and recourse to emergency caesarean section.

Monochorionic twin pregnancies of further increased complexity, such as monoamniotic twins,monochorionic twins with discordant anomalies or monochorionic twins within a tripletpregnancy are of even higher risk and early advice sought from units experienced in themanagement of these rare conditions.

References

1. Hack K, Derks J , Elias S, Franx A, Roos E, Voerman S, Bode C, Koopman-EsseboomC, Visser G. Increased perinatal mortality and morbidity in monochorionic versusdichorionic twin pregnancies: clinical implications of a large Dutch cohort study. BJ OG2008; 115: 58-67.

2. Sepulveda W, Sebire NJ , Hughes K. Evolution of the lambda or twin-chorionic peak signin dichorionic twin pregnancies. Obstet Gynecol 1997; 89: 439-441.

3. Lee Y, Wylie BJ , Simpson LL, DAlton ME. Twin Chorionicity and the Risk of Stillbirth.Obs Gyn 2008; 111: 310-8.

4. Senat MV, Deprest J , Boulvain M, Paupe A, Winer N, Ville Y. Endoscopic LaserSurgery versus Serial Amnioreduction for Severe Twin-to-Twin Transfusion Syndrome. NEngl J Med 2004; 351: 136-44.

5. Walker SP, Cole S and Edwards AG. Twin-to-twin transfusion syndrome: Is the futuregetting brighter? ANZOG 2007; 47: 158-168.

6. Chalouhi GE, Stirnemann J J , Salomon LJ , Essaoui M, Quibel T, Ville Y. Specificcomplications of monochorionic twin pregnancies: twin-twin transfusion syndrome andtwin reversed arterial perfusion sequence. Semin Fetal Neonatal Med 2010 Dec; 15 (6):349-56. Epub 2010 Sep 19. Review.

7. Slaghekke F, Kist WJ , Oepkes D, Pasman SA, Middeldorp J M, Klumper FJ , Walther FJ ,Vandenbussche FP, Lopriore E. Twin anemia-polycythemia sequence: diagnosticcriteria, classification, perinatal management and outcome. Fetal Diagn Ther 2010 J ul;27 (4): 181-90. Epub 2010 Mar 26.

8. The Royal College Obstetrician and Gynaecologists. Green-top GuidelineManagement

of Monochorionic Twin Pregnancy. Green-top 51, December 2008.
http://www.rcog.org.uk/womens-health/clinical-guidance/management-monochorionic-twin-pregnancyhttp://www.rcog.org.uk/womens-health/clinical-guidance/management-monochorionic-twin-pregnancyhttp://www.rcog.org.uk/womens-health/clinical-guidance/management-monochorionic-twin-pregnancyhttp://www.rcog.org.uk/womens-health/clinical-guidance/management-monochorionic-twin-pregnancy


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9. Thorson HL, Ramaeker DM, Emery SP. Optimal interval for ultrasound surveillance inmonochorionic twin gestations. Obstet Gynecol 2011; 117: 131-5.

Links to other College Statements

(C-Gen 02) Guidelines for consent and the provision of information regarding proposedtreatmenthttp://www.ranzcog.edu.au/component/docman/doc_download/899-c-gen-02-guidelines-for-consent-

and-the-provision-of-information-regarding-proposed-treatment-.html

(C-Gen 15) Evidence-based Medicine, Obstetrics and Gynaecologyhttp://www.ranzcog.edu.au/component/docman/doc_download/894-c-gen-15-evidence-based-medicine-obstetrics-and-gynaecology.html?Itemid=341

Disclaimer

This College Statement is intended to provide general advice to Practitioners. The statement should never be relied on as asubstitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient.

The statement has been prepared having regard to general circumstances. It is the responsibility of each Practitioner to haveregard to the particular circumstances of each case, and the application of this statement in each case. In particular, clinical

management must always be responsive to the needs of the individual patient and the particular circumstances of each case.

This College statement has been prepared having regard to the information available at the time of its preparation, and eachPractitioner must have regard to relevant information, research or material which may have been published or becomeavailable subsequently.

Whilst the College endeavours to ensure that College statements are accurate and current at the time of their preparation, it takesno responsibility for matters arising from changed circumstances or information or material that may have become available afterthe date of the statements.
http://www.ranzcog.edu.au/component/docman/doc_download/899-c-gen-02-guidelines-for-consent-and-the-provision-of-information-regarding-proposed-treatment-.htmlhttp://www.ranzcog.edu.au/component/docman/doc_download/899-c-gen-02-guidelines-for-consent-and-the-provision-of-information-regarding-proposed-treatment-.htmlhttp://www.ranzcog.edu.au/component/docman/doc_download/899-c-gen-02-guidelines-for-consent-and-the-provision-of-information-regarding-proposed-treatment-.htmlhttp://www.ranzcog.edu.au/component/docman/doc_download/894-c-gen-15-evidence-based-medicine-obstetrics-and-gynaecology.html?Itemid=341http://www.ranzcog.edu.au/component/docman/doc_download/894-c-gen-15-evidence-based-medicine-obstetrics-and-gynaecology.html?Itemid=341http://www.ranzcog.edu.au/component/docman/doc_download/894-c-gen-15-evidence-based-medicine-obstetrics-and-gynaecology.html?Itemid=341http://www.ranzcog.edu.au/component/docman/doc_download/894-c-gen-15-evidence-based-medicine-obstetrics-and-gynaecology.html?Itemid=341http://www.ranzcog.edu.au/component/docman/doc_download/899-c-gen-02-guidelines-for-consent-and-the-provision-of-information-regarding-proposed-treatment-.htmlhttp://www.ranzcog.edu.au/component/docman/doc_download/899-c-gen-02-guidelines-for-consent-and-the-provision-of-information-regarding-proposed-treatment-.html

c-obs 42 management of monochorionic twins new mar 11

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