Placental Characteristics of Monoamniotic Twin Pregnancies in Relation to Perinatal Outcome

Department of Obstetrics, Wilhelmina Children's Hospital, and Department of Pathology, University Medical Center Utrecht, Lundlaan 6, 3584 EA Utrecht, The Netherlands.
Placenta (Impact Factor: 2.71). 11/2008; 30(1):62-5. DOI: 10.1016/j.placenta.2008.09.016
Source: PubMed


To study placental characteristics in relation to perinatal outcome in 55 pairs of monochorionic monoamniotic (MA) twins.
Between January 1998 and May 2008 55 pairs of MA twins were delivered in 4 tertiary care centers and analysed for mortality, birth weight discordancy and twin-to-twin transfusion syndrome (TTTS) in relation to type of anastomoses, type and distance between cord insertions and placental sharing. Five acardiac twins, 2 conjoined twins, 4 higher order multiples and one early termination of pregnancy were excluded, leaving 43 MA placentas for analysis. Of these 43, one placenta could not be analysed for placental vascular anastomoses due to severe maceration after single intra-uterine demise leaving 42 placentas for analysis of anastomoses.
Arterio-arterial (AA), venovenous (VV) and arteriovenous (AV) anastomoses were detected in 98%, 43% and 91% of MA placentas, respectively. Velamentous cord insertion was found in 4% of cases. Small distance between both umbilical cord insertions (<5 cm) was present in 53% of MA placentas. Overall perinatal loss rate was 22% (19/86). We found no association between mortality and type of anastomoses, type and distance between cord insertions and placental sharing. The incidence of TTTS was low (2%) and occurred in the only pregnancy with absent AA-anastomoses.
Perinatal mortality in MA twins was not related to placental vascular anatomy. The almost ubiquitous presence of compensating AA-anastomoses in MA placentas appears to prevent occurrence of TTTS.

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Available from: Enrico Lopriore, Apr 08, 2015
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    • "The significant proximity of umbilical cord insertions may be a representative of the later splitting of inner cell mass in MA twin gestations (around 8e12 days after fertilization) compared to MC diamniotic twin gestations (around 4e8 days after fertilization). The short distance between cord insertions in MA placentas is reported to be one of the main causal factors leading to the ubiquitous entanglement of umbilical cords [7] [18]. This study also compared the angio-architecture in MC twin placentas with and without PCI. "
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    • "Median inter cord distance was 4 cm (range: 0e20 cm) [7]. Hack et al. (2009) determine that small distance between the insertions of both umbilical cords is a quite usual finding in MA twin gestations , thus severe complications in MA twin gestations, TTTS and cords entanglement and/or knotting are not related to the inter cord distance [7]. A review by Fraser et al. (1997) reported nine cases of single forked umbilical cord in MA twins in which the predominant causes for fetal death were severe fetal malformations [6]. "
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