D.P. Zhao

Prevalence, size, number and localization of vascular anastomoses in monochorionic placentas

INTRODUCTION Most monochorionic (MC) twin pregnancies have an uncomplicated course, but some develop severe complications including selective intrauterine growth restriction (sIUGR), twintwin transfusion syndrome (TTTS) and twin anemia-polycythemia sequence (TAPS). The underlying pathogenesis of these various complications is associated with the ubiquitous presence of vascular anastomoses in MC placentas. METHODS The aim of this study was to estimate the prevalence, number, size and localization of the anastomoses in sIUGR, TTTS and TAPS placentas compared to normal MC placentas using color dye injection. We excluded MC twin pregnancies treated with fetoscopic laser surgery or selective feticide. RESULTS A total of 235 placentas fulfilled the inclusion criteria: 126 normal MC, 47 TTTS, 46 sIUGR and 16 spontaneous TAPS. Median number of anastomoses in normal MC, sIUGR, TTTS and TAPS placentas was 8 (IQR: 4-12), 8 (IQR: 5-14), 7 (IQR: 5-11) and 4 (IQR: 3-5), respectively. The prevalence of arterio-arterial (AA) anastomoses in normal MC, sIUGR, TTTS and TAPS placentas was 96%, 98%, 47% and 19%, respectively. We found AV anastomoses to be evenly distributed along the vascular equator in all MC placentas except in TAPS cases, where anastomoses were mostly localized near the margin. We also found that, in sIUGR and TTTS placentas, AA anastomoses tended to be at the center of the placenta. CONCLUSION The present study shows that the prevalence, size, number and localization of the various types of anastomoses differ between normal MC, sIUGR, TTTS and TAPS placentas.

The role of veno-venous anastomoses in twin–twin transfusion syndrome

The aim of this study was to investigate the independent role of veno-venous (VV) anastomoses in the development of twin-twin transfusion syndrome (TTTS). Thirty TTTS placentas and 41 non-TTTS placentas, routinely injected with colored dye, were enrolled in this study. We excluded all cases with arterio-arterial (AA) anastomoses and TTTS cases treated with laser surgery. The prevalence of VV anastomoses was significantly higher in TTTS cases compared to non-TTTS cases, 37% (11/30) and 7% (3/41), respectively (P < .01; odds ratio 7.3; 95% confidence interval: 1.8-37.1). Our findings suggest that, in the absence of AA anastomoses, VV anastomoses may enhance the development of TTTS.

Placental share and hemoglobin level in relation to birth weight in twin anemia- polycythemia sequence

INTRODUCTION Twin anemia-polycythemia sequence (TAPS) is a newly described form of chronic twin transfusion. Previous observational studies noted a discordance between birth weight and individual placental share in TAPS. The purpose of this study was to investigate if fetal growth in monochorionic (MC) twins with TAPS is determined by placental share or by the net inter-twin blood transfusion. METHODS All consecutive MC twin placentas of live-born twin pairs with and without TAPS examined at our center between June 2002 and February 2014 were included in this study. Hemoglobin (Hb) levels and individual placental share were evaluated at birth and correlated with birth weight share. We excluded MC twin pregnancies with twin-twin transfusion syndrome. RESULTS A total of 270 MC twin pregnancies (TAPS group, n = 20; control group without TAPS, n = 250) were included in this study. Donors with TAPS had a lower birth weight than recipients in 90% (18/20) of cases, but a larger placental share in 65% (13/20) of cases. In the TAPS group, birth weight share was positively correlated with Hb share at birth (P < 0.01) but not with placental share (P = 0.54). In the control group without TAPS, birth weight share was strongly correlated with placental share (P < 0.01) but not with Hb share (P = 0.14). DISCUSSION A relatively larger placental share may enable the survival of the anemic twin in TAPS. CONCLUSION In contrast with uncomplicated MC twins, fetal growth in MC twins with TAPS is determined primarily by the net inter-twin blood transfusion instead of placental share.

Histologic Chorioamnionitis and Funisitis After Laser Surgery for Twin-Twin Transfusion Syndrome.

OBJECTIVE: To estimate the incidence of histologic chorioamnionitis and funisitis after fetoscopic laser surgery for the management of twin–twin transfusion syndrome. METHODS: A case–control study was performed at the Leiden University Medical Center from 2013 to 2014. All patients with twin–twin transfusion syndrome managed with laser surgery during the study period were included and compared with a control group of all monochorionic twins not treated with laser surgery. We excluded patients with fetal demise or higher order pregnancies. Placentas were reviewed for the presence and degree of chorioamnionitis and presence or absence of fetal inflammatory response. The primary outcome was the incidence of histologic chorioamnionitis and funisitis after laser surgery. Odds ratios (ORs) and 95% confidence intervals (CIs) for primary outcomes were calculated. A P value of <.05 was considered as statistical significance. RESULTS: Sixty-two patients treated with laser surgery were included in the study group and compared with 64 patients in the control group. The incidence of histologic chorioamnionitis was 13% (8/62) in the laser group compared with 5% (3/64) in the control group (OR 3.0, 95% CI 0.8–11.9, P=.12). Funisitis occurred in 8% (10/124) in the laser group compared with 0% in the control group (OR 11.1, 95% CI 1.3–96.9, P=.03). Histologic chorioamnionitis with or without funisitis after laser surgery was associated with a shorter laser-to-delivery interval (median 6.6 [range 3.4–14.1] compared with 13.6 [4.4–20.1] weeks, P<.01) and lower gestational age at birth (median 28.1 [range 23.1–32.6] compared with 32.7 [24.4–37.0] weeks, P<.01). CONCLUSION: These findings suggest that laser surgery for twin–twin transfusion syndrome is associated with an increased risk of funisitis.

Veno-venous anastomoses in twin-twin transfusion syndrome: A multicenter study.

INTRODUCTION The aim of this study is to evaluate the prevalence of veno-venous (VV) anastomoses in a large cohort of monochorionic (MC) twin placentas with twin-twin transfusion syndrome (TTTS) compared to a control group of MC placentas without TTTS. METHODS All TTTS placentas not treated with fetoscopic laser surgery (TTTS group) and examined at five international fetal therapy centers were included in this study and compared with a control group of MC placentas without TTTS (non-TTTS group). MC placentas were routinely injected with colored dye. We recorded the presence of VV and arterio-arterial (AA) anastomoses. RESULTS A total of 414 MC placentas were included in this study (TTTS group, n = 106; non-TTTS group, n = 308). The prevalence of VV anastomoses was significantly higher in the TTTS group than in the non-TTTS group, 36% (38/106) and 25% (78/308), respectively (p = .04; odds ratio (OR) 1.65; 95% confidence interval (CI): 1.03-2.64). In the subgroup of MC placentas without AA anastomoses, the prevalence of VV anastomoses in the TTTS group and non-TTTS group was 32% (18/57) and 8% (2/25), respectively (p = .03; OR: 5.31; 95% CI: 1.13-24.98). DISCUSSION VV anastomoses are detected more frequently in TTTS placentas than in MC placentas without TTTS and may thus play a role in the development of TTTS.

Monochorionic placentas with proximate umbilical cord insertions: Definition, prevalence and angio-architecture

INTRODUCTION Not much is known on the definition, occurrence and characteristics of proximate umbilical cord insertions (PCI) in monochorionic (MC) placentas. The purpose of this study was to establish a reference range for the distance between cord insertions and to evaluate the prevalence and angio-architecture of MC placentas with PCI. METHODS All MC placentas not treated with laser surgery were included in this study. The reference range of distance between cord insertions was created using the standard methodology proposed by Royston and Wright. We defined PCI as a cord insertion distance below the 5th centile. RESULTS AND DISCUSSION A total of 369 MC placentas were analyzed during this study period. The 5th centile was calculated by the equation: 0.027 × gestational age (weeks) +2.91 (cm), and ranged from 3.3 to 4 cm throughout gestation. Accordingly, 18 of the 369 (5%) MC placentas fulfilled the definition criteria for PCI. PCI occurred frequently in MC monoamniotic placentas (53%, 9/17) but were rare in MC diamniotic placentas (3%, 9/352). The prevalence of arterio-arterial and veno-venous anastomoses in MC placentas with and without PCI was respectively 100% versus 80% (P = .12) and 56% versus 26% (P = .01). PCI may be representative of later splitting of inner cell mass. CONCLUSION The threshold for PCI (5th centile) is approximately 4 cm throughout gestation. PCI are rare in MC diamniotic placentas, but are quite common in MC monoamniotic placentas. MC placentas with PCI are characterized by higher rates of superficial AA and/or VV anastomoses.

Increased Risk Of Early-Onset Neonatal Sepsis After Laser Surgery For Twin-to-Twin Transfusion Syndrome.

OBJECTIVE To investigate the occurrence of early-onset neonatal sepsis (EOS) in twin-twin transfusion syndrome (TTTS) managed with laser surgery. STUDY DESIGN We performed a prospective cohort study of all consecutive TTTS cases treated with laser surgery (TTTS group) delivered at the Leiden University Medical Center. We recorded the occurrence of EOS, defined as a positive blood culture ≤72 hours postpartum (proven sepsis) or administration of a full course of antibiotics due to risk factors or signs of sepsis, in the absence of a positive blood culture (suspected sepsis). Perinatal variables in the TTTS group were compared with uncomplicated monochorionic twins (no-TTTS group). A multivariate model was generated, examining the association between EOS and gestational age at birth, interval between laser surgery and birth, anterior placenta, laser period (first study period: 2002-2008; second study period: 2009-2015), and preterm premature rupture of membranes (PPROM). RESULTS The rates of combined suspected and proven EOS in the TTTS group and no-TTTS group were 16% (68/416) and 10% (55/542), respectively (relative ratio [RR] 1.74, 95% confidence interval [CI] 1.19-2.55). Multivariate analysis showed that EOS in the TTTS group was independently associated with lower gestational age at birth (odds ratio [OR] 0.75, 95% CI 0.63-0.88), first study period (OR 2.25, 95% CI 1.08-4.67) and PPROM (OR 2.47, 95% CI 1.28-4.75). CONCLUSION The rate of EOS in the TTTS group is low, but increased compared to the no-TTTS group. EOS in TTTS is independently associated with premature delivery, earlier laser period, and PPROM.

'Superficial' anastomoses in monochorionic placentas are not always superficial

Arterioarterial (AA) and venovenous (VV) anastomoses in monochorionic (MC) placentas lie on the placental surface and are termed as superficial anastomoses. The purpose of this study is to report the occurrence of an atypical form of superficial anastomoses which are partially hidden. Partially-hidden superficial anastomoses were defined as vascular anastomoses without visible direct connection on placental surface but with clear mixing of dye after colored dye injection. With analyzing 270 MC placentas, we found a prevalence of partially-hidden AA and VV anastomose of 3% and 5%, respectively. In conclusion, partially-hidden superficial anastomose are not infrequent in MC placentas.