Unequal placental sharing and birth weight discordance in monochorionic diamniotic twins

Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, CA, USA.
American journal of obstetrics and gynecology (Impact Factor: 3.97). 08/2006; 195(1):178-83. DOI: 10.1016/j.ajog.2006.01.015
Source: PubMed

ABSTRACT The purpose of this study was to define the association between unequal placental sharing and birth weight discordance in monochorionic/diamniotic twin pregnancies.
The study comprised a prospective cohort of monochorionic/diamniotic twin pregnancies who were delivered in Kaiser Permanente-Northern California, 1997-2003. Dye injection studies of fresh postpartum placentas were performed. Placental sharing, cord insertion combinations, vascular anastomoses, gestational age, and birth weights were recorded. Statistical comparisons of birth weight and gestational age were made with the Student t test. Rates of birth weight discordance were compared with the chi-square test. Multivariate logistic regression models analyzed the relationship between variables of interest.
Mean birth weights for larger and smaller twins were 2400 g and 2109 g, respectively. Twenty-two percent of the monochorionic/diamniotic twin pairs had birth weight discordance > or = 20%, and 8% of these pairs had twin-twin transfusion syndrome. Monochorionic/diamniotic twin pairs with unequal placental sharing had a 9.8 times greater likelihood of birth weight discordance (95% CI, 5.4-17.9) as compared with those pairs with equal placental sharing.
Unequal placental sharing is a significant risk factor for birth weight discordance in monochorionic/diamniotic twins. Antenatal diagnosis of unequal placental sharing would enable improved counseling in the setting of monochorionic/diamniotic twins.

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    • "In a large study of 116 MC twin placentas with BWD (>20%) Fick et al. found that MC twins with unequal sharing (>20% share discordance) had a 9.8 times greater likelihood of BWD (95% CI, 5.4e17.9) compared to MC twins with equal placental sharing [16]. "
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    ABSTRACT: To compare the placental characteristics in monochorionic (MC) twin pregnancies with and without birth weight discordance (BWD). We performed a matched case-control study to compare the placental characteristics of MC placentas from pregnancies with BWD (≥25%) (n = 47) with a control group of MC placentas without BWD (n = 47), matched for gestational age at birth. Placental sharing, angioarchitecture and diameter of the arterio-arterial (AA) anastomosis were assessed by placental injection with colored dye. The rate of velamentous cord insertion in MC placentas with and without BWD was 30% (28/94) and 16% (15/94), respectively (p = 0.036). Placental sharing discordance in MC placentas with and without BWD was 36% and 17%, respectively (p < 0.001). The mean diameter of the AA anastomosis in MC placentas with and without BWD was 2.2 mm and 1.8 mm, respectively (p = 0.024). MC placentas from growth-discordant twins are more unequally shared, have a higher rate of velamentous cord insertions and larger diameter of AA anastomosis compared to gestational age matched controls.
    Placenta 12/2011; 33(3):171-4. DOI:10.1016/j.placenta.2011.12.004 · 3.29 Impact Factor
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    • "birthweights than DC twins (Blickstein & Keith, 2004; Fick et al., 2006; Gielen et al., 2008; Gonzalez- Quintero et al., 2003). One would expect MZ DC twins to be the least discordant, because they are genetically identical, have their own placenta and, therefore, do not have to compete for nutrients. "
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    ABSTRACT: Both zygosity and chorionicity provide important information in twin research. The East Flanders Prospective Twin Survey (EFPTS) determines zygosity and chorionicity at birth and therefore provides a gold standard for the testing of diagnostic parameters that can be used to determine chorionicity. The aim of the present study was to investigate whether birthweight discordancy can be used as an indicator of chorionicity. The study sample consisted of 4,060 live-born twin pairs from the EFPTS. We studied MZ twins, using univariate and multivariate logistic regression analyses to calculate odds ratios (OR) and 95% confidence intervals (CI) of being MC in relation to discordancy level. Diagnostic parameters, including sensitivity and specificity, were calculated. A two-fold cross-validation was carried out and a bootstrap distribution with 10,000 samples was created to estimate the standard deviations. For discordancy levels of below 10%, 10-15%, 15-20%, 20-25% and above 25%, the ORs (95% CI) were 1.16 (0.91-1.47), 1.38 (1.05-1.80), 2.13 (1.51-3.01), 2.73 (1.73-4.29) and 2.81 (2.81-4.35) respectively. There were no gender differences. Sensitivity was 42.2% (SD 5.6%), specificity was 72.8% (SD 6.3%), positive predictive value was 72.8% (1.5%) and the negative predictive value was 39.2% (0.7%). In conclusion, although a higher discordancy level resulted in higher ORs of being an MC twin, birthweight discordancy level can only be used to some weak extent as a proxy for chorionicity, highlighting the need to assess and record chorionicity data in obstetrical units.
    Twin Research and Human Genetics 05/2009; 12(2):169-74. DOI:10.1375/twin.12.2.169 · 1.92 Impact Factor
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    • "Equal placental sharing was defined as 40–60% of placental weight attributed to each twin. Unequal placental sharing was defined as one twin receiving blood from >60% of the placenta [14]. Umbilical cord insertions were described as (para)central, marginal or velamentous. "
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    ABSTRACT: 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.
    Placenta 11/2008; 30(1):62-5. DOI:10.1016/j.placenta.2008.09.016 · 3.29 Impact Factor
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