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W4211035456 abstract "BJOG: An International Journal of Obstetrics & GynaecologyVolume 124, Issue 1 p. e1-e45 RCOG Green-top GuidelineFree Access Management of Monochorionic Twin Pregnancy Green-top Guideline No. 51 First published: 16 November 2016 https://doi.org/10.1111/1471-0528.14188Citations: 49AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat This is the second edition of this guideline, previously published under the same title in December 2008. Executive summary of recommendations Diagnosis of monochorionic twin pregnancy How is monochorionicity diagnosed prenatally and what is the accuracy of prenatal ultrasound chorionicity allocation? All women with a twin pregnancy should be offered an ultrasound examination between 11+0 weeks and 13+6 weeks of gestation (crown–rump length 45–84 mm) to assess fetal viability, gestational age and chorionicity, and to exclude major congenital malformations. Grade of recommendation: B Chorionicity should be determined at the time the twin pregnancy is detected by ultrasound based upon the number of placental masses, the appearance of the membrane attachment to the placenta and the membrane thickness. This scan is best performed before 14 weeks of gestation. [New 2016] Grade of recommendation: D A photographic (thermal copy) record should be taken and placed in the patient's notes documenting the ultrasound appearance of the membrane attachment to the placenta and an electronic copy stored (Appendix II). Grade of recommendation: ✓ If there is uncertainty about the diagnosis of chorionicity, a photographic record of the ultrasound appearance of the membrane attachment to the placenta should be retained and a second opinion should be sought. Grade of recommendation: ✓ If there is still doubt in the diagnosis of chorionicity, the woman should be referred to a specialist without delay, as chorionicity is best determined before 14 weeks of gestation. Grade of recommendation: D On ultrasound, the fetuses in twin pregnancies should be assigned nomenclature (i.e. upper and lower, or left and right) and this should be clearly documented in the woman's case notes to ensure consistency throughout pregnancy. [New 2016] Grade of recommendation: C Outcome of monochorionic twin pregnancy What is the outcome of monochorionic compared with dichorionic twin pregnancies? Clinicians and women should be aware that monochorionic twin pregnancies have higher fetal loss rates than dichorionic twin pregnancies, mainly due to second trimester loss and, overall, may have a higher risk of associated neurodevelopmental morbidity. This should form part of the parental counselling. Grade of recommendation: ✓ Optimal screening for chromosomal abnormalities, structural abnormalities and other fetal complications in monochorionic twin pregnancies What is the optimum method of screening for chromosomal abnormalities in monochorionic twin pregnancies? Women with monochorionic twins who wish to have aneuploidy screening should be offered nuchal translucency measurements in conjunction with first trimester serum markers (combined screening test) at 11+0 weeks to 13+6 weeks of gestation (crown–rump length 45–84 mm). [New 2016] Grade of recommendation: C In women with monochorionic twin pregnancies who ‘miss’ or who have unsuccessful first trimester screening for aneuploidy, second trimester screening by the quadruple test should be offered. [New 2016] Grade of recommendation: D Early data with noninvasive prenatal testing are encouraging, but results should be interpreted with caution until larger studies have been carried out. [New 2016] Grade of recommendation: C What is the optimum method of screening for structural abnormalities in monochorionic twin pregnancies? All monochorionic twins should undergo a routine detailed ultrasound scan between 18 and 20+6 weeks of gestation which includes extended views of the fetal heart anatomy (as recommended in the Fetal Anomaly Screening Programme screening of a singleton fetus). Grade of recommendation: C What is the optimum ultrasound regimen for monochorionic twin pregnancies? Fetal ultrasound assessment should take place every 2 weeks in uncomplicated monochorionic pregnancies from 16+0 weeks onwards until delivery (Appendix III). Grade of recommendation: D At every ultrasound examination, liquor volume in each of the amniotic sacs should be assessed and a deepest vertical pocket (DVP) depth measured and recorded, as well as the umbilical artery pulsatility index (UAPI). Fetal bladders should also be visualised. Although first presentation of twin-to-twin transfusion syndrome (TTTS) is rare after 26+0 weeks of gestation, it can occur and therefore, scans should be performed at 2-weekly intervals in uncomplicated monochorionic twins until delivery (Appendix III). [New 2016] Grade of recommendation: ✓ From 16+0 weeks of gestation, fetal biometry should be used to calculate an estimated fetal weight (EFW) and the difference in EFW calculated and documented. As the risk of selective growth restriction (sGR) extends to delivery, this should be performed at 2-weekly intervals until delivery. [New 2016] Grade of recommendation: D What are the optimum methods of screening for specific complications of monochorionic twin pregnancies? Screening for TTTS Screening for TTTS by first trimester nuchal translucency measurements should not be offered. [New 2016] Grade of recommendation: C Women with monochorionic twin pregnancies should be asked to report sudden increases in abdominal size or breathlessness to healthcare professionals in their secondary or tertiary centres as this may be a manifestation of TTTS. Grade of recommendation: ✓ Screening for TTTS should be by ultrasound examination from 16+0 weeks onwards, at 2-weekly intervals, noting and recording fetal biometry and liquor volumes (DVP). Fetal bladders should also be visualised. Grade of recommendation: ✓ Screening for twin anaemia-polycythaemia sequence (TAPS) TAPS should be screened for following fetoscopic laser ablation for TTTS and in other complicated monochorionic pregnancies requiring referral to a fetal medicine centre (such as those complicated by sGR) by serial middle cerebral artery peak systolic velocity (MCA PSV). [New 2016] Grade of recommendation: ✓ Screening for sGR At each scan from 20 weeks of gestation (at 2-weekly intervals) onwards, calculate EFW discordance using two or more biometric parameters. Calculate percentage EFW discordance using the following formula: ([larger twin EFW – smaller twin EFW]/larger twin EFW) x 100. Liquor volumes as DVP should be measured and recorded (to differentiate from TTTS). [New 2016] Grade of recommendation: C An EFW discordance of more than 20% is associated with an increase in perinatal risk. Such pregnancies should be referred for assessment and management in fetal medicine units with recognised relevant expertise. [New 2016] Grade of recommendation: B Umbilical artery Doppler evaluation in monochorionic twins with sGR allows definition of prognosis and potential morbidity. In particular, those with absent or reversed end-diastolic velocities (AREDV) and ‘cyclical’ umbilical artery Doppler waveforms (intermittent AREDV) are at increased risk of perinatal mortality and morbidity (Appendix IV). [New 2016] Grade of recommendation: C Management of complex pathologies associated with a monochorionic twin pregnancy The management of TTTS How useful are grading systems for severity of TTTS in establishing prognosis? At diagnosis, TTTS should be staged using the Quintero system. In addition, measurement of umbilical artery Doppler velocities, MCA PSV and ductus venosus Doppler studies should be performed and documented. Grade of recommendation: D What is (are) the optimal treatment(s) of TTTS and their outcomes? TTTS should be managed in conjunction with fetal medicine centres with recourse to specialist expertise and treatment in supraregional centres. Grade of recommendation: ✓ TTTS presenting before 26 weeks of gestation should be treated by fetoscopic laser ablation rather than amnioreduction or septostomy. There is evidence that the fetoscopic laser ablative method should be the Solomon technique. Grade of recommendation: A Centres performing fetoscopic laser ablation should perform at least 15 procedures per year (rolling 3-year average). [New 2016] Grade of recommendation: ✓ Weekly ultrasound assessment (including examination of the fetal brain, heart and limbs) and serial measurements of UAPI, MCA PSV and ductus venosus Doppler velocities should be performed. After 2 weeks post treatment, the ultrasound interval can be increased to every 2 weeks (noting UAPI, MCA PSV and DVP) with documentation of adequate fetal growth (by calculating EFW). Grade of recommendation: ✓ In treated TTTS pregnancies, ultrasound examination of the fetal heart should be performed by the fetal medicine specialist to exclude functional heart anomalies. Grade of recommendation: ✓ When should the delivery of monochorionic twin pregnancies complicated by TTTS take place? Delivery of monochorionic twin pregnancies previously complicated by TTTS and treated should be between 34+0 and 36+6 weeks of gestation. [New 2016] Grade of recommendation: D The management of sGR sGR in monochorionic twins requires evaluation in a fetal medicine centre with expertise in the management of such pregnancies. [New 2016] Grade of recommendation: ✓ In cases of early-onset sGR in association with poor fetal growth velocity and abnormal umbilical artery Doppler assessments, selective reduction may be considered an option. [New 2016] Grade of recommendation: C In sGR, surveillance of fetal growth should be undertaken at least every 2 weeks with fetal Doppler assessment (by umbilical artery and middle cerebral artery pulsatility index, and peak systolic velocity). If umbilical artery Doppler velocities are abnormal, the Doppler assessments should be undertaken in line with national guidance, measuring ductus venosus waveforms. [New 2016] Grade of recommendation: D Clinicians should be aware that there is a longer ‘latency period’ between diagnosis and delivery in monochorionic twins complicated by sGR compared with growth restriction in dichorionic twin pregnancy or singleton pregnancy. [New 2016] Grade of recommendation: D Abnormal ductus venosus Doppler waveforms (reversed flow during atrial contraction) or computerised cardiotocography short-term variation should trigger consideration of delivery. [New 2016] Grade of recommendation: B In type I sGR, planned delivery should be considered by 34–36 weeks of gestation if there is satisfactory fetal growth velocity and normal umbilical artery Doppler waveforms. [New 2016] Grade of recommendation: ✓ In type II and III sGR, delivery should be planned by 32 weeks of gestation, unless fetal growth velocity is significantly abnormal or there is worsening of the fetal Doppler assessment. [New 2016] Grade of recommendation: ✓ It is important to prospectively inform parents that in sGR and TTTS (even after apparently successful treatment) there can be acute transfusional events (which are neither predictable nor preventable) and therefore, despite regular monitoring, there may still be adverse perinatal outcomes. [New 2016] Grade of recommendation: ✓ Management of TAPS Clinicians should be aware that the natural history, fetal and neonatal implications, and optimal treatment and/or surveillance of monochorionic pregnancies diagnosed with TAPS are poorly established. [New 2016] Grade of recommendation: D The management of monochorionic twin pregnancies complicated by single twin demise What are the consequences for the surviving twin after fetal death of the co-twin in a monochorionic pregnancy and what is optimal clinical management? Clinicians should be aware that monochorionic pregnancies not complicated by TTTS, sGR or TAPS are still at risk of fetal death and neurological abnormality. Grade of recommendation: D After a single fetal death in a monochorionic pregnancy, clinicians should be aware that the risks to the surviving twin of death or neurological abnormality are of the order of 15% and 26%, respectively. [New 2016] Grade of recommendation: B Single fetal death in a monochorionic pregnancy should be referred and assessed in a fetal medicine centre, with multidisciplinary expertise to manage these cases. Grade of recommendation: ✓ Fetal magnetic resonance imaging of the brain may be performed 4 weeks after co-twin demise to detect neurological morbidity if this information would be of value in planning management. Grade of recommendation: D How should fetal anaemia be monitored after single twin intrauterine death? Fetal anaemia may be assessed by measurement of the fetal MCA PSV using Doppler ultrasonography. Grade of recommendation: D Timing and mode of delivery in uncomplicated monochorionic pregnancies What is the optimal timing and method of delivery for otherwise uncomplicated monochorionic pregnancies (without TTTS, sGR or TAPS)? Women with monochorionic twins should have timing of birth discussed and be offered elective delivery from 36+0 weeks with the administration of antenatal steroids, unless there is an indication to deliver earlier. [New 2016] Grade of recommendation: C It is appropriate to aim for vaginal birth of monochorionic diamniotic twins unless there are other specific clinical indications for caesarean section. Grade of recommendation: A Monochorionic monoamniotic (MCMA) pregnancies What are the specific problems of MCMA pregnancies and how should they be managed? MCMA twins almost always have umbilical cord entanglement when visualised using colour flow Doppler. Such a finding has not consistently been demonstrated to contribute to overall morbidity and mortality. [New 2016] Grade of recommendation: D MCMA twins have a high risk of fetal death and should be delivered by caesarean section between 32+0 and 34+0 weeks. [New 2016] Grade of recommendation: D Higher order multiple pregnancies with reference to monochorionicity What is the outcome of monochorionic and dichorionic compared with trichorionic triplet pregnancies? Clinicians should be aware that monochorionic/dichorionic triplet pregnancies have higher fetal loss rates than trichorionic triplet pregnancies and may be complicated by feto–fetal transfusion syndrome, sGR and TAPS. Grade of recommendation: C Selective reduction should be discussed in all higher order pregnancies including triplets. [New 2016] Grade of recommendation: ✓ Increased ultrasound surveillance is warranted in a fetal medicine centre with expertise to manage such cases. Grade of recommendation: ✓ Discordant abnormalities in monochorionic pregnancies What is the incidence of and the therapeutic options for discordant abnormalities in monochorionic pregnancies, including twin reversed arterial perfusion sequence? Monochorionic twins that are discordant for fetal anomaly must be referred promptly for assessment and counselling in a fetal medicine centre with consideration for treatment. Grade of recommendation: ✓ Karyotyping of monochorionic twins should be managed in a fetal medicine centre. [New 2016] Grade of recommendation: ✓ Meticulous mapping of the position of the twins within the uterus should be performed both at the time of prenatal diagnostic tests and invasive treatments. [New 2016] Grade of recommendation: ✓ During amniocentesis, both amniotic sacs should be sampled in monochorionic twin pregnancies, unless monochorionicity is confirmed before 14 weeks and the fetuses appear concordant for growth and anatomy. [New 2016] Grade of recommendation: ✓ Prior to invasive testing or in the context of twins discordant for an abnormality, selective reduction should be discussed and made available to those requesting the procedure after appropriate counselling. [New 2016] Grade of recommendation: ✓ Monitoring for disseminated intravascular coagulopathy is not indicated in monochorionic twin pregnancies undergoing selective reduction. [New 2016] Grade of recommendation: ✓ Selective feticide by intravascular injection of an abortifacient is not an option in monochorionic pregnancies because of the presence of placental anastomoses. The potential risks of intrafetal/umbilical cord ablative procedures should be discussed prospectively, including the risk of co-twin loss and neurological morbidity. [New 2016] Grade of recommendation: ✓ Documentation and discussion of heterokaryotypic monozygotic karyotypic abnormalities should take place. [New 2016] Grade of recommendation: ✓ Conjoined twins How are conjoined twins diagnosed and what are the outcomes? Conjoined twins are exceedingly rare and prenatal assessment is required in a tertiary fetal medicine centre so that diagnosis can be confirmed and prognosis discussed in conjunction with a multidisciplinary team. [New 2016] Grade of recommendation: ✓ What are the training competencies required for managing monochorionic pregnancies? All sonographers who undertake routine ultrasound scans during pregnancy must be trained to establish chorionicity and the correct labelling of twins. Grade of recommendation: ✓ All sonographers who undertake midtrimester (18 +0 –20 +6 weeks) and fetal growth scans of monochorionic twins should be made aware of the appearances of TTTS, sGR and TAPS, and the need to refer patients on to specialist centres if such features present. Grade of recommendation: ✓ Fetal medicine centres undertaking fetal therapy for relatively rare complications of monochorionic twins should have a minimum of two experienced operators and more than 15 cases per year (rolling 3-year average) to maximise perinatal outcomes and minimise long-term morbidity. Grade of recommendation: D 1 Purpose and scope The purpose of this guideline is to evaluate and provide recommendations on best practice for the management of problems associated with monochorionic placentation and their effects upon multiple pregnancies. The use of ultrasound to determine chorionicity and amnionicity is key to the management of multiple pregnancies and the potential risks to the fetuses. This guideline will outline the best evidence to guide clinical care, including fetal surveillance and treatment of complications for monochorionic multiple pregnancy. It is important to emphasise that this guideline is focused upon the management of monochorionic multiple pregnancies rather than all multiple pregnancies. It is also recognised that women carrying a monochorionic pregnancy (most commonly twins) may have concerns and anxieties surrounding their pregnancy. This requires accurate information given in a sensitive manner by healthcare professionals and support by a multidisciplinary team, ideally within a multiple pregnancy clinic.1 Support is also often given in conjunction with the Twins And Multiple Births Association and The Multiple Births Foundation within the UK. 2 Introduction and background epidemiology A monochorionic pregnancy is a multiple pregnancy, most commonly a twin pregnancy, in which babies are dependent on a single, shared placenta. Approximately 30% of twin pregnancies in the UK are monochorionic. Monochorionic placentation can also occur in rarer, higher order multiples, especially triplets (i.e. dichorionic or monochorionic triplets). There has been an increase in all types of multiple pregnancies with the increasing use of assisted reproductive technology, sociodemographic changes in our population associated with migration and deferment of pregnancy to a later maternal age. Assisted reproductive technology increases the prevalence of both dichorionic and monochorionic twinning. However, using day 5 blastocyst transfers seems to have a significantly higher rate of monozygotic twinning (adjusted OR 2.04, 95% CI 1.29–4.48) compared with cleavage stage day 3 transfers.2, 3 Monochorionic and dichorionic twin pregnancies have increased risks of preterm birth, fetal growth restriction (FGR), pre-eclampsia, postpartum haemorrhage and postnatal complications, such as infant feeding difficulties and adverse puerperal mood change.1, 4 The particular challenges of monochorionic pregnancies arise from the shared placenta and vascular placental anastomoses that are almost universal and connect the fetal circulations of both twins. Specific complications associated with inter-twin vascular anastomoses are listed in Table 1. Note that there may occasionally be some challenging diagnostic overlap among these definitions (e.g. twin-to-twin transfusion syndrome [TTTS] versus selective growth restriction [sGR] with reduced liquor around the smaller twin – see section 8.4.3): Table 1. Complications associated with inter-twin vascular anastomoses TTTS (Quintero staging) Associated with 15% of monochorionic twins I A significant discordance in amniotic fluid volumes. This is defined as oligohydramnios with deepest vertical pocket (DVP) < 2 cm in donor sac and polyhydramnios in the recipient sac (DVP > 8 cm before 20 weeks of gestation and > 10 cm after 20 weeks of gestation). Donor bladder visible and Doppler normal. II Bladder of the donor twin not visible and severe oligohydramnios due to anuria. Doppler studies are not critically abnormal. III Doppler studies are critically abnormal in either the donor or recipient, with typically abnormal umbilical arterial Doppler velocities in the donor and/or abnormal venous Doppler velocities in the recipient (reversed flow during atrial contraction within the ductus venosus and/or pulsatile umbilical vein velocities). IV Ascites, pericardial or pleural effusion, scalp oedema or overt hydrops present usually in the recipient. V One or both babies have died (not amenable to therapy). TAPS 2% of uncomplicated monochorionic diamniotic (MCDA) and up to 13% of monochorionic twins post laser ablation Signs of fetal anaemia in the donor and polycythaemia in the recipient without significant oligohydramnios/polyhydramnios being present. Donor has increased middle cerebral artery peak systolic velocity (MCA PSV) (> 1.5 multiples of the normal median) and recipient has decreased MCA PSV (< 1.0 multiples of the normal median). sGR (growth discordance of > 20%) Approximately 10–15% of monochorionic twins I Growth discordance but positive diastolic velocities in both fetal umbilical arteries. II Growth discordance with absent or reversed end-diastolic velocities (AREDV) in one or both fetuses. III Growth discordance with cyclical umbilical artery diastolic waveforms (positive followed by absent then reversed end-diastolic flow in a cyclical pattern over several minutes [intermittent AREDV; iAREDV]). TRAP sequence Approximately 1% of monochorionic twins Acardiac twin (with usually no cardiac tissue) being perfused by the anatomically ‘normal’ pump twin through a large artery–artery anastomosis on the placental surface. TTTS sGR twin anaemia-polycythaemia sequence (TAPS) twin reversed arterial perfusion (TRAP) sequence single intrauterine death; although not exclusive to monochorionic twin pregnancy, it is more common and has global effects on the co-twin. In addition, the consequences for single fetal death and the management of discordant fetal anomalies (i.e. structural and chromosomal anomalies) in monochorionic twins is important. Monochorionic diamniotic (MCDA) twin pregnancies carry a higher risk of overall fetal and perinatal loss compared with dichorionic pregnancies. Furthermore, monochorionic monoamniotic (MCMA) pregnancies, where both twins are in a single amniotic sac (1% of monochorionic twins), carry a very high risk of perinatal loss, most commonly before 24 weeks.1, 4-7 Almost all monochorionic placentas contain vascular anastomoses running between the two fetal umbilical cords within and on the surface of the placenta. These connect the fetal circulations. In 80% of cases, these are bidirectional vascular anastomoses which rarely lead to haemodynamic imbalance between the fetal circulations, but allow a direct vascular connection between the twins with an increased risk of fetal death.8, 9 In TTTS, which complicates up to 15% of monochorionic pregnancies,4 the placentas have a predominance of unidirectional artery–vein anastomoses. This may lead to a haemodynamic imbalance within the circulations of the twins, directly adversely affecting fetal cardiac function, fetoplacental perfusion, but also adversely affecting fetal renal function by discordant activation of the renin–angiotensin axis.4, 10 Postnatal perfusion studies have noted unequal placental ‘territory’ shared by the fetuses with associated marginal or ‘velamentous’ cord insertions. Such findings are common both in TTTS and sGR (which is often associated with TTTS).9, 11-13 Very rarely, TTTS complicates MCMA twin pregnancies, as well as both dichorionic and monochorionic triplet pregnancies.11, 14 TAPS is an important association in complicated monochorionic pregnancies, especially TTTS, occurring in up to 13% of cases post laser ablation.15 It may relatively rarely be associated with apparently uncomplicated MCDA twins. The pathogenesis of TAPS is evidenced by postnatal placental injection studies demonstrating ‘miniscule’ artery–vein anastomoses (less than 1 mm) allowing the slow transfusion of blood from the donor to the recipient. This may be associated with highly discordant haemoglobin levels at birth (80 g/l or greater).15-18 Significant intrauterine fetal size discordance (difference in estimated fetal weight [EFW] of greater than 20%), termed ‘selective growth restriction’ (sGR), occurs in up to 15% of monochorionic twins in the absence of TTTS and in over 50% of monochorionic twins complicated by TTTS.19 sGR is recognised as a specific monochorionic twin pathological entity associated with a significant differing placental territory between each fetus, inter-fetal placental anastomoses and abnormal fetoplacental blood flow.13 The incidence of size discordance is as great in dichorionic pregnancies in some series,20 but management of discordant growth is more complex in monochorionic pregnancies due to the associated placental anastomoses conjoining the fetal circulations. It is recognised that in monochorionic twin pregnancies, because of these potential and specific complications, there may be significant anxiety and concern in parents, even if such abnormalities are not present. Accurate information presented in a sensitive manner during discussions is important so as to allay unnecessary fears, while imparting to couples the importance of appropriate increased prenatal surveillance.1, 5, 6 3 Identification and assessment of evidence This guideline was developed in accordance with standard methodology for producing Royal College of Obstetricians and Gynaecologists (RCOG) Green-top Guidelines. The Cochrane Library (including the Cochrane Database of Systematic Reviews and the Database of Abstracts of Reviews of Effects [DARE]), EMBASE, Trip, MEDLINE and PubMed (electronic databases) were searched for relevant randomised controlled trials, systematic reviews and meta-analyses. The search was restricted to articles published between 1966 and 2015. The databases were searched using the relevant Medical Subject Headings (MeSH) terms, including all subheadings, and this was combined with a keyword search. Search words included ‘monochorionic twin’, ‘TTTS’, ‘twin twin transfusion syndrome’, ‘TRAP syndrome’, ‘amnioreduction’, ‘laser ablation’, ‘septostomy’ and ‘cord occlusion’ and the search was limited to humans and the English language. The National Library for Health and the National Guideline Clearinghouse were also searched for relevant guidelines and reviews. The most important of these is the 2011 National Institute for Health and Care Excellence (NICE) clinical guideline 129,1, 5 which was based upon an extensive review of the evidence for the antenatal management of twin and triplet pregnancies. An evidence update to this guideline was published in 2013.6 The proceedings of the 50th RCOG Study Group on Multiple Pregnancy also gave important expert opinion used in this document.4 In addition, qualitative information and patient representation has been provided by Mr Keith Reed on behalf of the Twins And Multiple Births Association and Ms Jane Denton on behalf of The Multiple Births Foundation. Where possible, recommendations are based on available evidence. In the absence of published evidence, these have been annotated as ‘good practice points’. Further information about the assessment of evidence and the grading of recommendations may be found in Appendix I. 4 Diagnosis of monochorionic twin pregnancy 4.1 How is monochorionicity diagnosed prenatally and what is the accuracy of prenatal ultrasound chorionicity allocation? All women with a twin pregnancy should be offered an ultrasound examination between 11+0 weeks and 13+6 weeks of gestation (crown–rump length 45–84 mm) to assess fetal viability, gestational age and chorionicity, and to exclude major congenital malformations. Grade of recommendation: B Chorionicity should be determined at the time the twin pregnancy is detected by ultrasound based upon the number of placental masses, the appearance of the membrane attachment to the placenta and the membrane thickness. This scan is best performed before 14 weeks of gestation. Grade of recommendation: D A photographic (thermal copy) record should" @default.
W4211035456 created "2022-02-13" @default.
W4211035456 date "2016-11-16" @default.
W4211035456 modified "2023-10-14" @default.
W4211035456 title "Management of Monochorionic Twin Pregnancy" @default.
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