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: 4.7). 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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    • "The causes of twin growth discordance are often unknown. The most important is considered to be monochorionicity, mainly because of unequal sharing, or of velamentous cord insertions in the IUGR twin [20]. Other possible causes are “intrauterine crowding” and the presence of malformations [21-23]. "
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    ABSTRACT: Background: Twins, compared to singletons, have an increased risk of perinatal mortality and morbidity, due mainly to a higher prevalence of preterm birth and low birthweight. Intrauterine growth restriction (IUGR) is also common and can affect one or both fetuses. In some cases, however, one twin is much smaller than the other (growth discordance). Usually, high birthweight discordance is associated with increased perinatal morbidity. The aim of this study is to describe the epidemiological features of a population of twins at birth, with particular reference to the interpretation and clinical effects of birthweight discordance. Methods: We evaluated retrospectively the clinical features of 70 infants born from twin pregnancies and assessed birthweight discordance in 31 pregnancies where both twins were followed at our institution. Discordance was treated both as a continuous and a categorical variable, using a cutoff of 18%. Possible relationships between birthweight discordance and other variables, such as maternal age, gestational age, birthweight percentile, number of SGA newborns in the pair, Hematocrit (Ht) discordance and neonatal anemia, prevalence of malformations, neonatal morbidity and death, were analyzed. Results: In our cohort birthweight percentile decreased slightly with increasing gestational age. Birthweight discordance, on the contrary, increased slightly with the increase of gestational age.A high discordance is associated to the presence of one SGA twin, with the other AGA or LGA. In our population, all 6 pregnancies in which discordance exceeded 18% belonged to this category (one SGA twin).Ht discordance at birth is associated to the presence of neonatal anemia in a twin, but it is not significantly related to weight discordance.Finally, in our case history, weight discordance is not associated in any way with the prevalence of malformations, morbidity and mortality. Conclusions: Birthweight discordance is an important indicator of complications that act asymmetrically on the two fetuses, affecting intrauterine growth in one of them, and usually determining the birth of a SGA infant.Our case history shows a significant statistical association between pair discordance and IUGR in one of the twins, but we could not demonstrate any relationship between discordance and the prevalence of malformations, morbidity and mortality.
    Italian Journal of Pediatrics 05/2014; 40(1):43. DOI:10.1186/1824-7288-40-43 · 1.52 Impact Factor
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    • "One group of children at risk for IUGR is twins and especially monochoriotic twins. Several studies have found that an unequal distribution of the placenta is a major reason for differences in birth weight and selective IUGR in monochoriotic twin pregnancies 43,86,87. This inequality could possibly be an effect of intertwin artery-to-artery anastomoses 88 (Fig. 1C). "
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    ABSTRACT: Early genetic and environmental factors have been discussed as potential causes for the high prevalence of asthma and allergic disease in the western world, and knowledge on fetal growth and its consequence on future health and disease development is emerging. This review article is an attempt to summarize research on fetal growth and risk of asthma and allergic disease. Current knowledge and novel findings will be reviewed and open research questions identified, to give basic scientists, immunologists and clinicians an overview of an emerging research field. PubMed-search on pre-defined terms and cross-references. Several studies have shown a correlation between low birth weight and/or gestational age and asthma and high birth weight and/or gestational age and atopy. The exact mechanism is not yet clear but both environmental and genetic factors seem to contribute to fetal growth. Some of these factors are confounders that can be adjusted for, and twin studies have been very helpful in this context. Suggested mechanisms behind fetal growth are often linked to the feto-maternal circulation, including the development of placenta and umbilical cord. However, the causal link between fetal growth restriction and subsequent asthma and allergic disease remains unexplained. New research regarding the catch-up growth following growth restriction has posited an alternative theory that diseases later on in life result from rapid catch-up growth rather than intrauterine growth restriction per se. Several studies have found a correlation between a rapid weight gain after birth and development of asthma or wheezing in childhood. Asthma and allergic disease are multifactorial. Several mechanisms seem to influence their development. Additional studies are needed before we fully understand the causal links between fetal growth and development of asthma and allergic diseases.
    Clinical & Experimental Allergy 10/2012; 42(10):1430-47. DOI:10.1111/j.1365-2222.2012.03997.x · 4.77 Impact Factor
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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 · 2.71 Impact Factor
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