Introduction
Twin-twin transfusion syndrome (TTTS) is a severe complication in monochorionic (MC) twin pregnancies, for which fetoscopic laser surgery is the preferred treatment. TTTS occurs in approximately 10% of MC pregnancies.1 2 3–5
This improving survival rate and decrease in perinatal complications have led to a shift in attention towards the long-term outcome of survivors of TTTS, especially the impact on neurodevelopment later in life. Neurodevelopment is an important outcome measure as it has a great influence on overall quality of life and academic achievement of children, burden on the family and on society.
The improved outcome in TTTS is a result of growing expertise and improved techniques, including the use of a selective sequential method and the Solomon laser technique.6 neurodevelopmental outcome after fetoscopic laser surgery for TTTS reported by studies from the last decade, 2009 to 2019.
Methods
A systematic literature search was performed to obtain all relevant articles. We searched PubMed, Embase, Emcare, Web of Science, Cochrane library, and Academic Search Premier using the following search (mesh) terms: fetofetal transfusion, fetoscopy, laser therapy, lasers, neurodevelopmental disorders, human development, cognition, cognition disorders, motor skills, cerebral palsy (CP), patient health questionnaire, neuropsychological tests, and neurobehavioral manifestations. For the complete search strategy see Supplemental Digital Content 1 (https://links.lww.com/MFM/A5 neurodevelopmental outcome in TTTS-survivors treated with fetoscopic laser surgery and assessed after the neonatal period using neurologic exams and cognitive developmental tests. Exclusion criteria were publications in other languages than English, reviews, case reports, guidelines, and letters. Reference lists of eligible studies were searched for relevant articles which were possibly missed by our search strategy. Eligibility and methodological quality of each study were assessed independently by two reviewers (P.K. and J.v.K.).
We searched eligible articles on neurodevelopmental primary and secondary outcomes, including CP, cognitive delay, blindness, and deafness. We registered lost to follow-up rates, reported risk factors and the tests used to determine cognitive delay and CP. Severe cognitive delay was defined as either a score below −2 standard deviations (SD ) on a developmental test or was based on the description of severe cognitive delay by the authors when no validated test was used. CP was classified as Grade I-V on the Gross Motor Function Classification System (GMFCS) or was based on other tests and reports of CP by the authors when GMFCS was not used.7
The primary outcome for this study was severe neurodevelopmental impairment (NDI), a composite of CP, severe motor and/or cognitive delay (<−2 SD ), bilateral blindness and/or bilateral deafness requiring amplification with hearing aids.
A secondary outcome was used to record adverse neurodevelopmental outcome as reported according to the various definitions in the included studies.
Data are reported as mean ± SD or median (interquartile range), as appropriate.
Results
Our search yielded 178 articles, 125 published between January 2009 and April 2019 (Fig. 1 ). In total, 26 articles met our inclusion criteria. We excluded seven articles because the same cohort was more fully described in later, larger or more detailed series by the same authors.8–14 15–17
Figure 1: Flowchart showing the selection of studies.
Long-term neurodevelopmental outcome in TTTS treated with laser surgery
From 1999 to 2009 only five long-term follow-up studies were published, compared to nineteen follow-up studies in the last decade, 2009 to 2019. Table 1 summarizes the long-term neurodevelopmental outcome stated as the prevalence of CP and NDI reported by these follow-up studies.
Table 1: Neurodevelopmental outcome in TTTS-survivors treated with laser therapy.
CP
The majority of studies (17/19) reported CP as a primary outcome or part of a composite outcome. The mean prevalence of CP was 5.1% (87/1700, 95% confidence interval (CI ): 4.1–6.2). Several tests were used to determine CP, including Amiel-Tison neurodevelopmental examination and other standard neurologic examinations. The GMFCS was used to classify CP by 4/19 (21.1%) studies.7
Cognitive outcome
To assess cognitive outcome, 6/18 (33.3%) studies used the ages stages questionnaire (ASQ), a developmental questionnaire for children aged 1 to 66 months and to be completed by parents.18–33 SD ranged between 6.0% and 42.4%. Salomon et al . (2010) followed-up a cohort from 6 months to 6 years of age and used both the ASQ at 12, 24, 48, and 60 months and the Wechsler Intelligence Scale for Children-IV at 6 years to evaluate cognitive development.19 SD was not reported. Korsakissok et al . (2018) and Schou et al . (2019) assessed 53.4% (31/58) and 68.0% of their cohorts with an ASQ.22,23 et al. (2019) reported a mean ASQ-score of (176.4 ± 51.5) at a median age of 27 months. In TTTS-survivors with a similar age (median 24 months), Lenclen et al. (2009) reported a mean ASQ-score of (216.3 ± 54).18
In 5/18 (27.7%) studies the Bayley scales second or third edition (Bayley II or III) was used to assess neurodevelopment.15–17,24,25 SD ranged from 3.2% to 15.8%, though only 3/5 studies presented these data.15,16,24 et al. (2009) conducted an international multicenter study in the Netherlands, Belgium, and Spain, the largest cohort in this review (n = 278).15 et al. (2016) evaluated their TTTS-survivors twice, first at 1 to 6 months followed by a second assessment at 7 to 12 months of age.25 et al . (2012) reported cognitive impairment in 6.8% (4/59) using Bayley scales with a cut-off point of <70.24
In 4/18 studies several tests were used according to the age range of their TTTS cohort. Gray et al. (2011) used both Griffith Mental Development Scales (Griffiths’ scales) (71.7%) and Bayley II and III (13.3% and 15.0%) to assess neurodevelopment and detected scores below −2 SD in 13 (11.5%) TTTS-survivors.26 et al. (2012) used the Kaufman-Assessment Battery for Children and the German national screening examination to assess cognitive and motor development in TTTS-survivors at a median age of 6 years and 5 months.27 et al. (2014) used the Wechsler Preschool and Primary Scale of Intelligence Third Edition in 41 children, in four (8.0%) children other tests were used, in five (10.0%) children neurodevelopment was considered normal based on parental reports.28 SD were detected in one child (2.0%). Vanderbilt et al . (2014) used the Battelle Developmental Inventory scores in 2-year-old TTTS-survivors and detected cognitive scores below −2 SD in one child (1.0%).29
In four studies, no validated test was used to assess neurodevelopment. Information on long-term outcome was obtained from parents, patient records, questionnaires, check-ups or the child's pediatrician.30–33 et al. (2015) described “neurodevelopmental concerns” in 14.1% (15/106) based on pediatric review and correspondence with parents.31
NDI
A wide variety of definitions was used to report neurodevelopmental outcome . The composite outcome “severe NDI” as defined in our Methods section was used in only 7/19 (36.8%) studies.15–17,22,23,26,29 CI : 7.8–11.5).
The majority of other follow-up studies used a different definition for NDI. Three studies reported a composite outcome including CP and a score below −2 SD on a developmental test, though lacking deafness and blindness.24,27,28 SD and four reported CP.20,21,25,32,33 Table 1 ).18,19,30,31 neurodevelopmental outcome when combining these different definitions is 10.5% (194/1 853, 95% CI : 9.1–11.9). Seven studies also included minor impairment defined as “borderline” scores or scores below −1 SD on developmental tests, minor neurological impairments, or temporary and treatable impairments with no significant impact on daily life (Table 2 ). The prevalence of minor impairment ranges between 0% and 25.9% with a summarized mean of 13.7% (117/853, 95% CI : 11.4–16.0).16,17,19,22,27,28,30
Table 2: Minor neurodevelopmental impairment in TTTS-survivors treated with laser therapy.
Control groups
Four studies compared neurodevelopmental outcome of TTTS-survivors with a control group of singletons, uncomplicated MC or dichorionic-twins. Campos et al . (2016) reported in both evaluations (1–6 and 7–12 months), more children in the TTTS group with an inadequate performance than in the control group of uncomplicated singletons.25 et al . (2019) reported lower ASQ scores for TTTS survivors with a median age of 27 months (range 11–60) compared to a control group of uncomplicated MC-twins of 18 months (range 17–25) (–23.5 points; 95% CI : –44.8 to –2.2, P = 0.03).23 P = 0.07). Lenclen et al . (2009) reported comparable ASQ scores in 85 TTTS-survivors born between 24 and 34 weeks of GA and assessed at the corrected age of 2 years and 184 DC-twin controls, (216.3 ± 54) versus (225.5 ± 54) respectively (P = not significant).18 et al. (2018) described the outcome in TTTS-survivors born <29 weeks of GA at a corrected age of eighteen months.32 P = 0.07).
Risk factors
An important characteristic of long-term outcome studies is the possibility to assess (perinatal) risk factors for long-term impairment. All nineteen studies included for this review assessed risk factors for their primary outcome.
The severity of TTTS, defined as Quintero Stage I to V, is reported a risk factor for adverse outcome in 5/12 (41.6%) studies.17,19,21,26,29,34 neurodevelopmental outcome . In contrast, Sananès et al. (2016) reported an association between Quintero Stage I, indicating less severe disease, and abnormal ASQ scores (P = 0.021).21 P = 0.004), leading to possible selection bias, since lost to follow-up was 49.5% (54/109) in Stage II, 38.6% (27/70) in Stage III, and 37.5% (3/8) in Stage IV.
Prematurity and low birth weight, in particular fetal growth restriction or being small for GA, are well-known risk factors for adverse long-term outcome. Low GA at birth was reported a risk factor for adverse long-term neurodevelopmental outcome in 30.7% (4/13) studies.15,17,21,22 et al. (2018) reported a high prevalence of CP (15.4%) in very premature infants (<29 weeks of GA) born after laser therapy for TTTS.32 et al. (2012), 90.9% (10/11) children with severe neurological morbidity (see definition in Table 1 ) were born before 32 weeks of gestation.30 et al . (2019) reported CP or ASQ-scores below −2 SD in 23.1% of TTTS-survivors born before 34 weeks of gestation versus 6.6% in survivors born after a GA of 34 weeks.23
Low birth weight was reported as a risk factor for long-term impairment in 44.4% (4/9) studies.15,17,21,22 et al. (2019) reported an independent association between cognitive scores and low birth weight (regression coefficient B: 0.3; 95% CI : 0.1–0.6, P = 0.004) and between cognitive scores and growth restriction below the tenth percentile (regression coefficient B: −4.3; 95% CI : −7.9 to −0.7, P = 0.021).17 et al . (2016) described an association between birth weight below the fifth percentile and adverse neurodevelopmental outcome (P = 0.036): 23.1% (9/39) children with a birth weight below the fifth percentile had an abnormal ASQ.21 et al. (2009) found low birth weight associated with NDI (odds ratio: 1.2 for each 100-g decrease; 95% CI: 1.1–1.3; P < 0.001) though no association between NDI and growth restriction below the tenth percentile.15
Graeve et al . (2012) described significantly better Kaufman-Assessment Battery for Children mental processing scores in recipients compared to donors (median 106 (69–127) and 100 (70–124) respectively, P = 0.045), though no significant difference in overall scores.27 et al . (2016) reported an association between donor status and difficulties with expressive communication (odds ratio: 6.8, 95% CI : 1.0–44.6).25
In one study, cranial magnetic resonance imaging (MRI) was routinely performed in the whole study population. Chang et al. (2012) described impairment in one child with no cerebral injury on MRI and two children with cerebral injury on MRI and normal neurologic exams.24 el al . (2019) reported an association between decreased Bayley motor scores and severe cerebral injury (regression coefficient B: −14.1; 95% CI : −25.0 to −3.2, P = 0.012), although 58.8% (10/17) of children with NDI had no severe cerebral injury on cranial ultrasound.17
Maternal education was associated with scores on the Battelle Developmental Inventory by Vanderbilt et al. (2014).29 P < 0.001) than lower GA at birth (β level 0.3, P < 0.01) and advanced Quintero stage (β level −0.4, P < 0.01). In contrast, Campos et al. (2016) reported no association between impairment and maternal education, although they did find an association between impairment and economic class, defined according to the Brazilian Association of Research Companies, (each point decreased the risk of abnormality with 16%).25
Discussion
In the past decade, fetal medicine centers all over the world increasingly reported on the long-term neurodevelopmental outcome after fetoscopic laser surgery for TTTS. Overall, in the last 10 years, 19 studies evaluated the long-term neurodevelopmental outcome . Severe NDI was reported in seven studies and the prevalence of severe NDI was 9.7% (range 4.0%–18.0%). The prevalence of adverse neurodevelopmental outcome (our secondary outcome) was 10.5% (Table 1 ) and the prevalence of CP was 5.1%. Minor impairment was reported in 13.7%.
Important risk factors for adverse long-term neurodevelopmental outcome include prematurity, low birth weight, and advanced Quintero stage. The association between Quintero stage and long-term impairment suggests that increasing disease severity may not only lead to increased perinatal mortality but also to increased long-term morbidity. Recipient or donor status of the fetus was not associated with adverse neurodevelopmental outcome in most studies, although two studies found lower scores on one domain. The prognostic value of severe antenatal or postnatal cerebral injury for long-term impairment remains a subject of debate. Conclusions on long-term neurodevelopmental outcome based on cerebral injury are difficult to make as cerebral injury does not directly correlate with long-term neurodevelopment. The prevalence of minor impairment implies that, even in children without obvious NDI, subtle problems may occur, including mild CP and neurocognitive impairments. These “subtle” problems can have a significant impact on the care and educational requirements of children throughout life.
The prevalence of NDI and CP in this review is equivalent to the prevalence described in a recent review by Hecher et al . (2018), reporting NDI in 6% to 18% and CP in 3% to 11% of TTTS-survivors.35 et al . (2011) and van Klink et al . (2016) reported mean NDI in 11.1% and 9.8% and CP in 4.8% and 6.1%, respectively.36,37 36,37
In several studies bias may have occurred, the majority due to an unequal distribution of Quintero stages in the follow-up group, as no Quintero Stage I cases were included or a higher proportion of low or high Quintero stages were lost to follow-up.21,26,28,29 21,22,29,32 23
An important limitation for comparison between studies is the substantial difference in the timing of follow-up (age range from 1 month to 10 years), their definition of the primary outcome, inclusion criteria, and the methods and materials to assess outcome. The majority of studies performed their assessments at an adjusted age of 2 years. At this age, it is possible to discover severe developmental abnormalities that require and benefit from early intervention. However, developmental outcomes assessed during early childhood are only moderate predictors of long-term neurodevelopment, particularly for scores on cognitive tests and academic performance. Although some studies followed their cohort until a mean of five years of age, some developmental problems, including learning difficulties, speech and language deficits, and communication disorders, cannot be detected until later on, once the children start becoming more socially and academically challenged at school age. In addition, definitions of primary outcome ranged widely from CP to impaired cognitive function, sometimes including blindness and hearing impairment. The aforementioned composite outcome, NDI, was unfortunately used in less than half of the included studies. Therefore, the mean prevalence of NDI must be interpreted with caution as it is based on a minority of the reported impairment. In these studies, different neurodevelopmental tests were used, like Bayley II and III, ASQ, as well as nonvalidated questionnaires and neurologic exams. Results were either reported as mean scores per domain of the developmental test, the proportion of children with abnormal results per domain or only overall scores, which makes it difficult to compare results between studies.
Longer follow-up of TTTS-survivors is required to understand the clinical relevance of milder forms of impairments diagnosed in early childhood and to follow speech and language development, for instance at the age of 2, 5, and 8 years. Studies reporting on long-term neurodevelopment should use a uniform definition of NDI that is, scores on neurodevelopmental tests below −2 SD , CP GMFCS grade II or higher, bilateral blindness and/or severe hearing impairment. In this review, we had to include all grades of CP in the composite outcome NDI since most studies did not report or grade CP according to GMFCS. To reliably compare study results, it is important that diagnoses of individual cases are reported and in particular when there are comorbidities. Only TTTS-survivors treated with laser surgery should be included in follow-up along with an appropriate control group. When other groups are included in follow-up, presentation of separate results on primary and secondary outcomes are recommended. Validated neurodevelopmental test is of uttermost importance to assess neurodevelopment. Methods sections should contain a detailed description of the used definitions and methods. In the results section authors should report both mean scores, including SD , per domain and on the overall test, and the proportion of children with scores below −2 SD . Consensus on these terms is necessary to allow valid comparison of cohorts, which would improve the quality of research and lead to more accurate knowledge on TTTS. Accordingly, development of a core outcome set to allow comparison of study data would be beneficial in improving the quality of research.38,39
Moreover, large prospective multicenter studies with stringent neuroimaging and long-term follow-up protocols could provide more clarity around the association between cerebral injury and NDI.
In conclusion, TTTS-survivors are at increased risk for NDI and close fetal monitoring and long-term follow-up remains required. Continuing follow-up until at least school age is recommended. International collaboration in long-term follow-up of TTTS-survivors to form universal inclusion criteria, developmental tests, ages at assessment, and outcome measures are of great importance to improve knowledge on long-term neurodevelopmental outcome and allow adequate parental counseling.
Acknowledgment
The authors thank J.W. Schoones for assistance with the literature search strategy.
Funding
None.
Conflicts of Interest
None.
References
[1]. Lewi L, Jani J, Blickstein I, et al. The outcome of monochorionic diamniotic twin gestations in the era of invasive fetal therapy: a prospective cohort study. Am J Obstet Gynecol 2008;199:514.e511–e518. doi:10.1016/j.ajog.2008.03.050.
[2]. Berghella V, Kaufmann M. Natural history of twin-twin transfusion syndrome. J Reprod Med 2001;46(5):480–484.
[3]. van Klink JM, Koopman HM, van Zwet EW, et al. Cerebral injury and neurodevelopmental impairment after amnioreduction versus laser surgery in twin-twin transfusion syndrome: a systematic review and meta-analysis. Fetal Diagn Ther 2013;33(2):81–89. doi:10.1159/000341814.
[4]. Senat MV, Deprest J, Boulvain M, et al. Endoscopic laser surgery versus serial amnioreduction for severe twin-to-twin transfusion syndrome. N Engl J Med 2004;351(2):136–144. doi:10.1056/NEJMoa032597.
[5]. Rossi AC, D’Addario V. Laser therapy and serial amnioreduction as treatment for twin-twin transfusion syndrome: a metaanalysis and review of literature. Am J Obstet Gynecol 2008;198(2):147–152. doi:10.1016/j.ajog.2007.09.043.
[6]. Slaghekke F, Lopriore E, Lewi L, et al. Fetoscopic laser coagulation of the vascular equator versus selective coagulation for twin-to-twin transfusion syndrome: an open-label randomised controlled trial. Lancet 2014;383(9935):2144–2151. doi:10.1016/s0140-6736(13)62419-8.
[7]. Palisano R, Rosenbaum P, Walter S, et al. Development and reliability of a system to classify gross motor function in children with cerebral palsy. Dev Med Child Neurol 1997;39(4):214–223. doi:10.1111/j.1469-8749.1997.tb07414.x.
[8]. Arias AV, Campos D, Campos-Zanelli TM, et al. Twin-twin transfusion syndrome: neurodevelopmental screening test. Arq Neuropsiquiatr 2015;73(3):194–199. doi:10.1590/0004-282x20140237.
[9]. Chmait RH, Chon AH, Schrager SM, et al. Fetal brain-sparing after laser surgery for twin-twin transfusion syndrome appears associated with two-year neurodevelopmental outcomes. Prenat Diagn 2016;36(1):63–67. doi:10.1002/pd.4713.
[10]. Chmait RH, Chon AH, Schrager SM, et al. Neonatal cerebral lesions predict 2-year neurodevelopmental impairment in children treated with laser surgery for twin-twin transfusion syndrome. J Matern Fetal Neonatal Med 2019;32(1):80–84. doi:10.1080/14767058.2017.1371694.
[11]. Chon AH, Mamey MR, Schrager SM, et al. The relationship between preoperative fetal head circumference and 2-year cognitive performance after laser surgery for twin-twin transfusion syndrome. Prenat Diagn 2018;38(3):173–178. doi:10.1002/pd.5204.
[12]. van Klink JM, Koopman HM, van Zwet EW, et al. Improvement in
neurodevelopmental outcome in survivors of twin-twin transfusion syndrome treated with laser surgery. Am J Obstet Gynecol 2014;210(6):540.e1-e7. doi:10.1016/j.ajog.2014.01.002.
[13]. Ortibus E, Lopriore E, Deprest J, et al. The pregnancy and long-term
neurodevelopmental outcome of monochorionic diamniotic twin gestations: a multicenter prospective cohort study from the first trimester onward. Am J Obstet Gynecol 2009;200(5):494.e1-e8. doi:10.1016/j.ajog.2009.01.048.
[14]. Peralta CF, Molina FS, Gomez LF, et al. Endoscopic laser dichorionization of the placenta in the treatment of severe twin-twin transfusion syndrome. Fetal Diagn Ther 2013;34(4):206–210. doi:10.1159/000354898.
[15]. Lopriore E, Ortibus E, Acosta-Rojas R, et al. Risk factors for neurodevelopment impairment in twin-twin transfusion syndrome treated with fetoscopic laser surgery. Obstet Gynecol 2009;113(2 Pt 1):361–366. doi:10.1097/AOG.0b013e318195873e.
[16]. van Klink JM, Slaghekke F, Balestriero MA, et al.
Neurodevelopmental outcome at 2 years in twin-twin transfusion syndrome survivors randomized for the Solomon trial. Am J Obstet Gynecol 2016;214:113.e1–e7. doi:10.1016/j.ajog.2015.08.033.
[17]. Spruijt MS, Lopriore E, Tan R, et al. Long-term
neurodevelopmental outcome in twin-to-twin transfusion syndrome: is there still room for improvement? J Clin Med 2019;8(8). doi:10.3390/jcm8081226.
[18]. Lenclen R, Ciarlo G, Paupe A, et al.
Neurodevelopmental outcome at 2 years in children born preterm treated by amnioreduction or fetoscopic laser surgery for twin-to-twin transfusion syndrome: comparison with dichorionic twins. Am J Obstet Gynecol 2009;201(3):291.e1-e5. doi:10.1016/j.ajog.2009.05.036.
[19]. Salomon LJ, Ortqvist L, Aegerter P, et al. Long-term developmental follow-up of infants who participated in a randomized clinical trial of amniocentesis vs laser photocoagulation for the treatment of twin-to-twin transfusion syndrome. Am J Obstet Gynecol 2010;203(5):444.e1-e7. doi:10.1016/j.ajog.2010.08.054.
[20]. Tosello B, Blanc J, Haumonte JB, et al. Short and medium-term outcomes of live-born twins after fetoscopic laser therapy for twin-twin transfusion syndrome. J Perinat Med 2014;42(1):99–105. doi:10.1515/jpm-2013-0119.
[21]. Sananes N, Gabriele V, Weingertner AS, et al. Evaluation of long-term neurodevelopment in twin-twin transfusion syndrome after laser therapy. Prenat Diagn 2016;36(12):1139–1145. doi:10.1002/pd.4950.
[22]. Korsakissok M, Groussolles M, Dicky O, et al. Mortality, morbidity and 2-years neurodevelopmental prognosis of twin to twin transfusion syndrome after fetoscopic laser therapy: a prospective, 58 patients cohort study. J Gynecol Obstet Hum Reprod 2018;47(10):555–560. doi:10.1016/j.jogoh.2018.04.003.
[23]. Schou KV, Lando AV, Ekelund CK, et al. Long-term
neurodevelopmental outcome of monochorionic twins after laser therapy or umbilical cord occlusion for twin-twin transfusion syndrome. Fetal Diagn Ther 2019;46(1):20–27. doi:10.1159/000491787.
[24]. Chang YL, Chao AS, Chang SD, et al. The neurological outcomes of surviving twins in severe twin-twin transfusion syndrome treated by fetoscopic laser photocoagulation at a newly established center. Prenat Diagn 2012;32(9):893–896. doi:10.1002/pd.3929.
[25]. Campos D, Arias AV, Campos-Zanelli TM, et al. Twin-twin transfusion syndrome: neurodevelopment of infants treated with laser surgery. Arq Neuropsiquiatr 2016;74(4):307–313. doi:10.1590/0004-282x20160032.
[26]. Gray PH, Poulsen L, Gilshenan K, et al.
Neurodevelopmental outcome and risk factors for disability for twin-twin transfusion syndrome treated with laser surgery. Am J Obstet Gynecol 2011;204(2):159.e1-e6. doi:10.1016/j.ajog.2010.08.041.
[27]. Graeve P, Banek C, Stegmann-Woessner G, et al.
Neurodevelopmental outcome at 6 years of age after intrauterine laser therapy for twin-twin transfusion syndrome. Acta Paediatr 2012;101(12):1200–1205. doi:10.1111/apa.12017.
[28]. McIntosh J, Meriki N, Joshi A, et al. Long term developmental outcomes of pre-school age children following laser surgery for twin-to-twin transfusion syndrome. Early Hum Dev 2014;90(12):837–842. doi:10.1016/j.earlhumdev.2014.08.006.
[29]. Vanderbilt DL, Schrager SM, Llanes A, et al. Predictors of 2-year cognitive performance after laser surgery for twin-twin transfusion syndrome. Am J Obstet Gynecol 2014;211(4):388.e1-e7. doi:10.1016/j.ajog.2014.03.050.
[30]. Kowitt B, Tucker R, Watson-Smith D, et al. Long-term morbidity after fetal endoscopic surgery for severe twin-to-twin transfusion syndrome. J Pediatr Surg 2012;47(1):51–56. doi:10.1016/j.jpedsurg.2011.10.021.
[31]. Mullers SM, McAuliffe FM, Kent E, et al. Outcome following selective fetoscopic laser ablation for twin to twin transfusion syndrome: an 8 year national collaborative experience. Eur J Obstet Gynecol Reprod Biol 2015;191:125–129. doi:10.1016/j.ejogrb.2015.05.019.
[32]. Sommer J, Nuyt AM, Audibert F, et al. Outcomes of extremely premature infants with twin-twin transfusion syndrome treated by laser therapy. J Perinatol 2018;38(11):1548–1555. doi:10.1038/s41372-018-0202-z.
[33]. Swiatkowska-Freund M, Pankrac Z, Preis K. Results of laser therapy in twin-to-twin transfusion syndrome: our experience. J Matern Fetal Neonatal Med 2012;25:1917–1920. doi:10.3109/14767058.2012.668585.
[34]. Quintero RA, Morales WJ, Allen MH, et al. Staging of twin-twin transfusion syndrome. J Perinatol 1999;19(8 Pt 1):550–555. doi:10.1038/sj.jp.7200292.
[35]. Hecher K, Gardiner HM, Diemert A, et al. Long-term outcomes for monochorionic twins after laser therapy in twin-to-twin transfusion syndrome. Lancet Child Adolesc Health 2018;2(7):525–535. doi:10.1016/S2352-4642(18)30127-5.
[36]. Rossi AC, Vanderbilt D, Chmait RH. Neurodevelopmental outcomes after laser therapy for twin-twin transfusion syndrome: a systematic review and meta-analysis. Obstet Gynecol 2011;118(5):1145–1150. doi:10.1097/AOG.0b013e318231827f.
[37]. van Klink JM, Koopman HM, Rijken M, et al. Long-term
neurodevelopmental outcome in survivors of twin-to-twin transfusion syndrome. Twin Res Hum Genet 2016;19(3):255–261. doi:10.1017/thg.2016.26.
[38]. Khalil A, Perry H, Duffy J, et al. Twin-twin transfusion syndrome: study protocol for developing, disseminating, and implementing a core outcome set. Trials 2017;18(1):325. doi:10.1186/s13063-017-2042-0.
[39]. Perry H, Duffy JMN, Reed K, et al. Core outcome set for research studies evaluating treatments for twin-twin transfusion syndrome. Ultrasound Obstet Gynecol 2019;54(2):255–261. doi:10.1002/uog.20183.
