Title: Placental types and twin-twin transfusion syndrome
Abstract: To the Editors:Bermudez et al,1Bermudez C Becerra CH Bornick PW Allen MH Arroyo J Quintero RA Placental types and twin-twin transfusion syndrome.Am J Obstet Gynecol. 2002; 187: 489-494Abstract Full Text Full Text PDF PubMed Scopus (86) Google Scholar in proposing a classification system for monochorionic (MC) placental anatomy, report that 79% (19/24) of pregnancies with mixed superficial and deep anastomoses have twin-twin transfusion syndrome (TTTS) and that 81% (21/26) of MC pregnancies without TTTS have no deep arteriovenous (AV) anastomoses. Because these extraordinary findings contradict previous studies,2Machin G Still K Lalani T Correlations of placental vascular anatomy and clinical outcomes in 69 monochorionic twin pregnancies.Am J Med Genet. 1996; 61: 229-236Crossref PubMed Scopus (168) Google Scholar, 3Denbow ML Cox P Taylor M Hammal DM Fisk NM Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome.Am J Obstet Gynecol. 2000; 182: 417-426Abstract Full Text Full Text PDF PubMed Scopus (349) Google Scholar their methods used for their ex vivo placental injection study warrant critical examination.First, surely laser treatment invalidates postnatal injection studies because not only are the anastomoses destroyed months earlier in vivo but also their respective cotyledons. We note that no pictures were provided of any postablation anastomoses. Second, the injection of air rather than the more modern colored dye technique renders detection problematic because only by demonstrating mixing of dyes within a shared cotyledon can the presence of deep AV anastomoses be confirmed.3Denbow ML Cox P Taylor M Hammal DM Fisk NM Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome.Am J Obstet Gynecol. 2000; 182: 417-426Abstract Full Text Full Text PDF PubMed Scopus (349) Google Scholar Third, fewer than one fifth of placentas studied were from pregnancies without TTTS, suggesting huge referral bias. Fourth, 45 of 176 (26%) of placentas were excluded from their study, which may have biased their findings if these were from more advanced-stage TTTS with single or double intrauterine death, possibly as a result of laser treatment of the wrong vessels. Fifth, parametric statistics are inappropriate for nonnormally distributed data (ie, mean number of anastomoses without TTTS = 1.77, SD 1.27), and the authors need to represent their entire data either nonparametrically or categorically.These methodologic flaws undermine the authors' principal conclusion that superficial anastomoses are not protective against TTTS. In any case, reanalysis of their own data prompts the opposite conclusion. Thus, 85 of 89 (96%) of those without, and 20 of 42 (48%) of those with, superficial anastomoses had TTTS (χ2, P <.0001). Indeed, only 20 of 105 (19%) patients with TTTS had superficial anastomoses, in keeping with our studies and those of others.2Machin G Still K Lalani T Correlations of placental vascular anatomy and clinical outcomes in 69 monochorionic twin pregnancies.Am J Med Genet. 1996; 61: 229-236Crossref PubMed Scopus (168) Google Scholar, 3Denbow ML Cox P Taylor M Hammal DM Fisk NM Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome.Am J Obstet Gynecol. 2000; 182: 417-426Abstract Full Text Full Text PDF PubMed Scopus (349) Google ScholarBased on their erroneous findings, the authors suggest that ultrasound scanning for superficial anastomoses in MC twins is unwarranted. However, in vivo studies of arterioarterial anastomoses (AAAs) have confirmed that AAAs not only protect against the development of TTTS but also improve outcome in established disease in the minority who have TTTS with an AAA. Thus, in our study of 105 consecutive MC pregnancies, to which the authors fail to refer, the chance for development of TTTS was reduced 9-fold when an AAA was identified by color Doppler imaging.4Taylor MJ Denbow ML Tanawattanacharoen S Gannon C Cox PM Fisk NM Doppler detection of arterio-arterial anastomoses in monochorionic twins: feasibility and clinical application.Hum Reprod. 2000; 15: 1632-1636Crossref PubMed Scopus (92) Google Scholar Furthermore, in a smaller study of TTTS, also not acknowledged, outcome was significantly improved in those in whom an AAA was identified at diagnosis.5Taylor MJ Denbow ML Duncan KR Overton TG Fisk NM Antenatal factors at diagnosis that predict outcome in twin-twin transfusion syndrome.Am J Obstet Gynecol. 2000; 183: 1023-1028Abstract Full Text PDF PubMed Scopus (93) Google Scholar Review of our more recent experience shows that, overall, fetal and neonatal survival is twice as high when AAAs are detected compared with when they are not (35/42 [83%] vs 41/102 [40%], χ2 P <.0001). To the Editors:Bermudez et al,1Bermudez C Becerra CH Bornick PW Allen MH Arroyo J Quintero RA Placental types and twin-twin transfusion syndrome.Am J Obstet Gynecol. 2002; 187: 489-494Abstract Full Text Full Text PDF PubMed Scopus (86) Google Scholar in proposing a classification system for monochorionic (MC) placental anatomy, report that 79% (19/24) of pregnancies with mixed superficial and deep anastomoses have twin-twin transfusion syndrome (TTTS) and that 81% (21/26) of MC pregnancies without TTTS have no deep arteriovenous (AV) anastomoses. Because these extraordinary findings contradict previous studies,2Machin G Still K Lalani T Correlations of placental vascular anatomy and clinical outcomes in 69 monochorionic twin pregnancies.Am J Med Genet. 1996; 61: 229-236Crossref PubMed Scopus (168) Google Scholar, 3Denbow ML Cox P Taylor M Hammal DM Fisk NM Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome.Am J Obstet Gynecol. 2000; 182: 417-426Abstract Full Text Full Text PDF PubMed Scopus (349) Google Scholar their methods used for their ex vivo placental injection study warrant critical examination.First, surely laser treatment invalidates postnatal injection studies because not only are the anastomoses destroyed months earlier in vivo but also their respective cotyledons. We note that no pictures were provided of any postablation anastomoses. Second, the injection of air rather than the more modern colored dye technique renders detection problematic because only by demonstrating mixing of dyes within a shared cotyledon can the presence of deep AV anastomoses be confirmed.3Denbow ML Cox P Taylor M Hammal DM Fisk NM Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome.Am J Obstet Gynecol. 2000; 182: 417-426Abstract Full Text Full Text PDF PubMed Scopus (349) Google Scholar Third, fewer than one fifth of placentas studied were from pregnancies without TTTS, suggesting huge referral bias. Fourth, 45 of 176 (26%) of placentas were excluded from their study, which may have biased their findings if these were from more advanced-stage TTTS with single or double intrauterine death, possibly as a result of laser treatment of the wrong vessels. Fifth, parametric statistics are inappropriate for nonnormally distributed data (ie, mean number of anastomoses without TTTS = 1.77, SD 1.27), and the authors need to represent their entire data either nonparametrically or categorically.These methodologic flaws undermine the authors' principal conclusion that superficial anastomoses are not protective against TTTS. In any case, reanalysis of their own data prompts the opposite conclusion. Thus, 85 of 89 (96%) of those without, and 20 of 42 (48%) of those with, superficial anastomoses had TTTS (χ2, P <.0001). Indeed, only 20 of 105 (19%) patients with TTTS had superficial anastomoses, in keeping with our studies and those of others.2Machin G Still K Lalani T Correlations of placental vascular anatomy and clinical outcomes in 69 monochorionic twin pregnancies.Am J Med Genet. 1996; 61: 229-236Crossref PubMed Scopus (168) Google Scholar, 3Denbow ML Cox P Taylor M Hammal DM Fisk NM Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome.Am J Obstet Gynecol. 2000; 182: 417-426Abstract Full Text Full Text PDF PubMed Scopus (349) Google ScholarBased on their erroneous findings, the authors suggest that ultrasound scanning for superficial anastomoses in MC twins is unwarranted. However, in vivo studies of arterioarterial anastomoses (AAAs) have confirmed that AAAs not only protect against the development of TTTS but also improve outcome in established disease in the minority who have TTTS with an AAA. Thus, in our study of 105 consecutive MC pregnancies, to which the authors fail to refer, the chance for development of TTTS was reduced 9-fold when an AAA was identified by color Doppler imaging.4Taylor MJ Denbow ML Tanawattanacharoen S Gannon C Cox PM Fisk NM Doppler detection of arterio-arterial anastomoses in monochorionic twins: feasibility and clinical application.Hum Reprod. 2000; 15: 1632-1636Crossref PubMed Scopus (92) Google Scholar Furthermore, in a smaller study of TTTS, also not acknowledged, outcome was significantly improved in those in whom an AAA was identified at diagnosis.5Taylor MJ Denbow ML Duncan KR Overton TG Fisk NM Antenatal factors at diagnosis that predict outcome in twin-twin transfusion syndrome.Am J Obstet Gynecol. 2000; 183: 1023-1028Abstract Full Text PDF PubMed Scopus (93) Google Scholar Review of our more recent experience shows that, overall, fetal and neonatal survival is twice as high when AAAs are detected compared with when they are not (35/42 [83%] vs 41/102 [40%], χ2 P <.0001). Bermudez et al,1Bermudez C Becerra CH Bornick PW Allen MH Arroyo J Quintero RA Placental types and twin-twin transfusion syndrome.Am J Obstet Gynecol. 2002; 187: 489-494Abstract Full Text Full Text PDF PubMed Scopus (86) Google Scholar in proposing a classification system for monochorionic (MC) placental anatomy, report that 79% (19/24) of pregnancies with mixed superficial and deep anastomoses have twin-twin transfusion syndrome (TTTS) and that 81% (21/26) of MC pregnancies without TTTS have no deep arteriovenous (AV) anastomoses. Because these extraordinary findings contradict previous studies,2Machin G Still K Lalani T Correlations of placental vascular anatomy and clinical outcomes in 69 monochorionic twin pregnancies.Am J Med Genet. 1996; 61: 229-236Crossref PubMed Scopus (168) Google Scholar, 3Denbow ML Cox P Taylor M Hammal DM Fisk NM Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome.Am J Obstet Gynecol. 2000; 182: 417-426Abstract Full Text Full Text PDF PubMed Scopus (349) Google Scholar their methods used for their ex vivo placental injection study warrant critical examination. First, surely laser treatment invalidates postnatal injection studies because not only are the anastomoses destroyed months earlier in vivo but also their respective cotyledons. We note that no pictures were provided of any postablation anastomoses. Second, the injection of air rather than the more modern colored dye technique renders detection problematic because only by demonstrating mixing of dyes within a shared cotyledon can the presence of deep AV anastomoses be confirmed.3Denbow ML Cox P Taylor M Hammal DM Fisk NM Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome.Am J Obstet Gynecol. 2000; 182: 417-426Abstract Full Text Full Text PDF PubMed Scopus (349) Google Scholar Third, fewer than one fifth of placentas studied were from pregnancies without TTTS, suggesting huge referral bias. Fourth, 45 of 176 (26%) of placentas were excluded from their study, which may have biased their findings if these were from more advanced-stage TTTS with single or double intrauterine death, possibly as a result of laser treatment of the wrong vessels. Fifth, parametric statistics are inappropriate for nonnormally distributed data (ie, mean number of anastomoses without TTTS = 1.77, SD 1.27), and the authors need to represent their entire data either nonparametrically or categorically. These methodologic flaws undermine the authors' principal conclusion that superficial anastomoses are not protective against TTTS. In any case, reanalysis of their own data prompts the opposite conclusion. Thus, 85 of 89 (96%) of those without, and 20 of 42 (48%) of those with, superficial anastomoses had TTTS (χ2, P <.0001). Indeed, only 20 of 105 (19%) patients with TTTS had superficial anastomoses, in keeping with our studies and those of others.2Machin G Still K Lalani T Correlations of placental vascular anatomy and clinical outcomes in 69 monochorionic twin pregnancies.Am J Med Genet. 1996; 61: 229-236Crossref PubMed Scopus (168) Google Scholar, 3Denbow ML Cox P Taylor M Hammal DM Fisk NM Placental angioarchitecture in monochorionic twin pregnancies: relationship to fetal growth, fetofetal transfusion syndrome, and pregnancy outcome.Am J Obstet Gynecol. 2000; 182: 417-426Abstract Full Text Full Text PDF PubMed Scopus (349) Google Scholar Based on their erroneous findings, the authors suggest that ultrasound scanning for superficial anastomoses in MC twins is unwarranted. However, in vivo studies of arterioarterial anastomoses (AAAs) have confirmed that AAAs not only protect against the development of TTTS but also improve outcome in established disease in the minority who have TTTS with an AAA. Thus, in our study of 105 consecutive MC pregnancies, to which the authors fail to refer, the chance for development of TTTS was reduced 9-fold when an AAA was identified by color Doppler imaging.4Taylor MJ Denbow ML Tanawattanacharoen S Gannon C Cox PM Fisk NM Doppler detection of arterio-arterial anastomoses in monochorionic twins: feasibility and clinical application.Hum Reprod. 2000; 15: 1632-1636Crossref PubMed Scopus (92) Google Scholar Furthermore, in a smaller study of TTTS, also not acknowledged, outcome was significantly improved in those in whom an AAA was identified at diagnosis.5Taylor MJ Denbow ML Duncan KR Overton TG Fisk NM Antenatal factors at diagnosis that predict outcome in twin-twin transfusion syndrome.Am J Obstet Gynecol. 2000; 183: 1023-1028Abstract Full Text PDF PubMed Scopus (93) Google Scholar Review of our more recent experience shows that, overall, fetal and neonatal survival is twice as high when AAAs are detected compared with when they are not (35/42 [83%] vs 41/102 [40%], χ2 P <.0001).
Publication Year: 2003
Publication Date: 2003-04-01
Language: en
Type: letter
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 16
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