Twin Birth Weight Discordance Research Articles

Birth weight discordance and adverse neonatal outcomes in appropriately grown premature twins

ObjectiveThis study aimed to analyze the clinical characteristics of birth weight discordant twins (BWDT) who were premature and appropriate-for-gestational-age or large-for-gestational-age. Additionally, it assessed the impact of birth weight discordance on the prognosis of appropriately grown premature twins, and investigated the effect of maternal factors on neonatal outcomes. Study designThis retrospective cohort study included twins who were born alive after preterm labor at the Nanjing Drum Tower Hospital from January 2018 to December 2021, along with their mothers. Twins were arranged into discordant and concordant groups according to intertwin birth weight discordance, followed by the analysis of the clinical characteristics of mothers and the prognosis of neonates. ResultsA total of 585 mothers and 1170 neonates were included, with 47 mothers and 94 neonates in the discordant group. The incidence of birth weight discordance was 8.0% (94/1,170) in appropriately grown premature twins. The incidence of complications (43.2% vs. 21.8%) and transfer to the neonatal intensive care unit (NICU) (53.2% vs. 29.2%) was higher in the discordant group than in the concordant group (p < 0.05). Furthermore, the incidence of infectious diseases (36.7% vs. 19.4%), necrotizing enterocolitis (7.6% vs. 1.6%), and oxygen therapy rate (22.8% vs. 12.8%) were statistically significantly higher in the discordant group than in the concordant group (p < 0.05). ConclusionBirth weight discordance remains a high-risk factor for complications and transfer to the NICU in appropriately grown premature twins. It is important to pay attention to birth weight discordance when the outcomes of twins are assessed.

Twin births in Yucatan, Mexico during 2008–2020: trends in maternal sociodemographic factors and differences in birth weight and length according to sex of co-twin

Background: Over the years, there has been a noticeable increase in the incidence of multiple pregnancies, due in part to the increased use of assisted reproductive technologies in recent years. The increase in twin pregnancies constitutes a public health challenge due to the adverse outcomes sometimes they entail. Twin pregnancies inherently carry a higher risk of complications, and one of the critical associated factors is the risk of low birth weight. Twin birth weight discordance among different populations can be attributed to differences in non-shared environmental influences. The presence of two or more fetuses in the uterus may lead to an unequal distribution of nutritional and oxygen resources, increasing the likelihood that at least one of the twins will experience insufficient fetal development. Other factors, such as ethnicity, genetics, sociodemographic characteristics, gestational age, parity, and chorion type, have also been related to the birth weight discordance in twin pregnancies. However, it is unclear to what extent the associations between these factors can explain the differences in birth and length size. The frequency of twin births varies among populations and over time, so it is crucial to gain a deeper understanding of the factors contributing to the rise in the twinning rate. The official records of twins continue to make significant contributions to our understanding of the causes of individual differences, and new twin registries are still being created. The recent availability of data from developing countries allows the analysis of trends in regions with sociodemographic and reproductive profiles. Obtaining a more comprehensive understanding of the epidemiology, as well as the related morbidity and mortality, is clinically crucial. Objectives: The aim of the study was to describe the trends of twin births in Yucatan, Mexico during 2008–2021, analyze their association with maternal sociodemographic factors, and compare birth outcomes between types of twin pairs: female-female, male-male, and female-male. Methods: A retrospective cohort analysis was conducted using data from the Mexican Ministry of Health, encompassing information on all births registered in the State of Yucatán, Mexico, from 2008 through 2021. The data was obtained from both public and private hospitals. The variables, including date of birth, sex, gestational age, birth weight and length of newborns, mother´s date of birth, educational level, and number of previous live offspring, were extracted from each dataset. Multiple births (three or more) were excluded from the study. We graphically analyzed the rates (per 1000 births) and percentages of twins according to maternal age, education level, and parity during the study period. A multiple logistic regression model was used to analyze the association between maternal sociodemographic factors and the occurrence of twin births. Comparisons of the gestational age and birth weight and length between types of twin pairs were performed using analysis of variance. Results: A total of 478,118 live births, including 1.4% twins (accounting 6,766 twin births), were analyzed. The rates increased from 11.21 during 2008–2011 to 13.34 during 2012–2017 and reached 20.08 in 2019. The percentages increased in women aged ≥30 years and those with higher educational levels. Older maternal age (coefficient = 0.03; OR = 1.03, per each year), greater education level (coefficient = 0.55 and OR= 1.74 for medium and coefficient = 1.05; OR = 2.57 for high level, compared with no education) and higher parity (coefficient= 0.26; OR = 1.30 per each previous offspring) increased the odds for having twins. Twins’ male-male showed a slightly increased of preterm birth than a co-twin female. Opposite-sex twins showed measurable but small increases in birth weight and length compared with same-sex twins. Conclusion: The rate of twins in Yucatan increased substantially during 2008–2020 in specific sociodemographic groups. Opposite-sex twins were slightly larger than same-sex twins at birth.

Impact of assisted reproductive technology on birth weight discordance in twins

To explore the association between assisted reproductive technology (ART) and birth weight discordance in twins (BWDT). A retrospective analysis was conducted on twin infants born between January 2011 and December 2020 at the Third Affiliated Hospital of Guangzhou Medical University, with complete basic birth data. The impact of ART on the occurrence of BWDT was identified by the multivariate logistic regression analysis. A total of 3 974 pairs of twins were included, with 1 431 conceived naturally and 2 543 through ART. Neonates in the ART group had higher birth weights than those in the naturally conceived group (P<0.001). The incidence of BWDT was lower in the ART group compared to the naturally conceived group (16.17% vs 21.09%, P<0.001). The multivariate logistic regression analysis, adjusting for confounding factors such as maternal age, parity, pre-pregnancy body mass index, gestational diabetes, hypothyroidism, gestational age, and chorionic properties, showed no significant difference in the risk of BWDT between the ART and naturally conceived groups (P>0.05). ART is not associated with the risk of BWDT.

The impact of placental anastomoses and umbilical cord insertions’ sites on monochorionic twin pregnancy outcomes: Evidence from color-dye injection studies

IntroductionOur knowledge of monochorionic pregnancies’ complications is largely based on the extensive ongoing research on monochorionic placental structure. Previous studies on the concordance of umbilical cord insertions are limited. This study aimed to evaluate placental anastomoses and cord insertions as independent risk factors for neonatal adverse outcomes. MethodsThis was a prospective study conducted at Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy from April 2021 to December 2022. Seventy-six women with a monochorionic pregnancy were enrolled at their first-trimester scan. After delivery, all placentas that were confirmed to be monochorionic were analyzed according to standard protocols, including those of complicated monochorionic twin pregnancies. The primary outcomes were a Composite Monochorionic Pregnancy Outcome (CMPO) and a Composite Neonatal Adverse Outcome (CNAO). The secondary outcome was the birth weight discordance between the neonates. ResultsThe CMPO occurred in 15.8 % pregnancies, and the CNAO occurred in 67.1 % pregnancies. The analysis confirmed a significant association between velamentous cord insertions and neonatal adverse events (p = 0.003). Also, a significant positive association (p = 0.0326) between twin birth weight discordance and discordance in twins umbilical cord insertions’ sites was found. No significant association between the number and type of the anastomoses and both the CMPO or CNAO was detected. DiscussionOur data suggest that the routine sonographic assessment of umbilical cords' insertion sites during the first trimester could be helpful in predicting fetal and neonatal adverse events. We believe that this sonographic assessment should start to be implemented in our routine care of monochorionic pregnancies.

Role of birthweight discordance in preterm twins' outcomes in the Korean neonatal network.

Twin pregnancies can be complicated by birthweight (BW) discordance. We analyzed the impact of BW discordance on clinical outcomes of very-low-birthweight (VLBW) twins. The study population was preterm infants in the Korean Neonatal Network registry. Multivariate logistic regression analyses were used to determine the contribution of BW discordance on respiratory morbidities and mortality of VLBW infants. Also, we assessed the effect of small for gestational age (SGA) on morbidity and mortality in discordant twins (DTs) and compared separately the clinical outcomes of smaller and larger DTs with different singletons matched for perinatal factors including BW percentile. A total of 935 twin pairs [1548 concordant twins (CTs) and 322 DTs] were included. BW discordance was associated with increased odds of moderate bronchopulmonary dysplasia, mortality, and composite outcomes. Compared with the CTs, the smaller, but not larger, DTs had greater odds of morbidities and mortality. DTs had higher odds of adverse neonatal outcome when combined with SGA. Meanwhile, DTs had morbidities and mortality similar to singletons matched for BW percentile. BW discordance in VLBW twins adversely affects neonatal mortality or respiratory morbidity which is predominant in smaller DTs. The impact of BW discordance could be increased through SGA.

Impact of placental sharing and large bidirectional anastomoses on birthweight discordance in monochorionic twins: a retrospective cohort study in 449 cases

In monochorionic twin pregnancies, the fetuses share a single placenta. When this placenta is unequally shared, a discordant antenatal growth pattern ensues resulting in high rates of perinatal morbidity and mortality. Understanding placental pathophysiology is paramount in devising feasible antenatal management strategies. Unequal placental sharing is not the sole determinant of birthweight discordance as there is no one-to-one relationship with placental share discordance. Placental angioarchitecture, especially the presence of large bidirectional anastomoses, is thought to affect this relationship by allowing for a compensatory intertwin blood flow. This study aimed to assess whether placental angioarchitecture can affect birthweight discordance in live-born monochorionic twins, the aim of our study was 2-fold: (1) to assess the relationship between birthweight discordance and placental share discordance and (2) to examine to what extent large bidirectional anastomoses can compensate for the effect of unequal placental sharing on birthweight discordance, with a subgroup analysis for umbilical artery Doppler flow patterns in cases with a birthweight discordance of ≥20%. This was a retrospective cohort study that included monochorionic twin pregnancies observed in our center between March 2002 and June 2021, in which twins with a birthweight discordance of ≥20% were classified according to umbilical artery Doppler flow patterns of the smaller twin. We excluded cases with twin-twin transfusion syndrome and twin anemia polycythemia sequence. Monochorionic placentas of live-born twins were injected with dye, and images were saved for computer measurements of placental sharing and the diameter of anastomoses. Univariate linear regressions of the relationship between placental share discordance and birthweight discordance (both calculated as weight or share larger twin-weight or share smaller twin/weight or share larger twin×100%) and the relationship between arterioarterial and venovenous diameters and birthweight ratio/placental territory ratio were performed. A total of 449 placentas were included in the analysis. Placental share discordance was positively correlated with birthweight discordance (β coefficient, 0.325; 95% confidence interval, 0.254-0.397; P<.0001). The arterioarterial diameter was negatively correlated with birthweight ratio/placental territory ratio (β coefficient,-0.041; 95% confidence interval,-0.059 to-0.023; P<.0001), meaning that an increase in arterioarterial diameter leads to less birthweight discordance than expected for the amount of placental share discordance. There was no relationship between venovenous diameter and birthweight ratio/placental territory ratio (β coefficient,-0.007; 95% confidence interval,-0.027 to 0.012; P=.473). Birthweight discordance in monochorionic twins was strongly associated with placental share discordance. Large arterioarterial anastomoses can mitigate the effect of unequal placental sharing.

Maternal Thyroid Function and Birth Weight in Twins.

ContextThyroid hormones are associated with birth weight in singleton pregnancy. Twin pregnancies need more thyroid hormones to maintain the normal growth and development of the fetuses compared with single pregnancy.ObjectiveWe aimed to investigate the association of thyroid hormones and birth weight in twins.MethodsThis was a retrospective cohort study in a Chinese population. Pregnant women who received regular antenatal health care and delivered live-born twins from 2014 to 2019 were included (n = 1626). Linear mixed model with restricted cubic splines and logistic regression models were used to estimate the association of thyroid hormones with birth weight and birth weight discordance in twins.ResultsWe observed that both thyrotropin (TSH) and free thyroxine (FT4) were not associated with birth weight in twins overall, while when stratifying on fetal sex or chorionicity, there were nonlinear association between FT4 levels and birth weight in boys (Pnonlinear < .001) and in dichorionic (DC) twins (Pnonlinear = 0.03). Women with levels of FT4 lower than the 10th percentile had a higher risk of birth weight discordance in their offspring than women with normal FT4 levels (range, 2.5 to 97.5 percentiles) (odds ratio = 1.58; 95% CI, 1.05-2.33).ConclusionOur study suggests there was an association of FT4, but not TSH, with birth weight and birth weight discordance varied by sex and chorionicity. These findings could have implications for obstetricians to be aware of the importance of FT4 levels in preventing birth weight discordance in twin pregnancy.

Long-term neurodevelopmental outcome in discordant twin : A nationwide population-based study in South Korea

Discordant twin is associated with increased perinatal mortality and/or morbidities. The long-term neurodevelopmental outcome has been evaluated in a few studies with small number of cases and the results are conflicting. In this nationwide population-based study, we aimed to evaluate the long-term neurodevelopmental outcomes between the birthweight discordant twin (≥20%) and concordant twins, and between the larger and the smaller twin within the pairs.

130 Twin birthweight discordance and adverse neonatal outcomes

The impact of intertwin birthweight discordance on neonatal outcomes remains unclear. We compared adverse neonatal outcomes between concordant and discordant twins, controlling for fetal growth and chorionicity. Retrospective cohort study of twins categorized as small, appropriate, and large for gestational age (SGA 90%ile respectively), using a twin-specific US nomogram stratified by chorionicity (Anath et al). Discordance was analyzed at 15% and 20% cutoffs in two groups: 24 0/7-33 6/7 and 34 0/7-38 6/7 weeks. Pre-specified composite primary neonatal outcome included respiratory distress syndrome requiring mechanical ventilation, 5-min Apgar <4, intraventricular hemorrhage (IVH) grade III or IV, necrotizing enterocolitis, neonatal sepsis, neonatal intensive care unit (NICU) admission >1 week, and neonatal death. Composite secondary neonatal outcome included IVH grade I-II, transient tachypnea, hypoglycemia, hyperbilirubinemia, and NICU admission ≤1 week. Outcomes were compared between concordant and discordant twins and adjusted for potential confounders including chorionicity, SGA, hypertensive disorders, antenatal steroids, gestational age at delivery, and delivery mode. 1213 twin sets were analyzed. In unadjusted analyses, both primary and secondary outcomes were significantly greater at both ≥15% and ≥20% discordance in both gestational age groups (all p<.05). In the adjusted models, primary outcome was still significantly greater at both ≥15% and ≥20% discordance at 24 0/7-33 6/7, but not at 34 0/7-38 6/7 weeks (Table). Neither degree of discordance was significantly associated with the secondary outcome in either gestational age group in the adjusted analyses (Table). In twins born at <34 0/7 weeks, intertwin birthweight discordance ≥15% was significantly associated with increased odds of adverse primary, but not secondary, neonatal outcomes, even when controlled for chorionicity and SGA status. Degree of discordance was not associated with adverse neonatal outcomes with delivery at later gestational ages.

Ultrasound in the prediction of birthweight discordance in dichorionic twins.

Large birthweight discrepancy has been identified as a risk factor for perinatal morbidity and mortality in twin pregnancies. However, it remains unclear whether such discordance can be predicted by various biological indices with specific cut-off values, and how these depend on the gestational age. We aimed to determine the most effective way to predict large birthweight discordance at various gestational ages. A retrospective cohort study of dichorionic twins, live-born between 2008 and 2018, was conducted. Discordances in biparietal diameter, head circumference, humerus and femur length, abdominal circumference, and estimated fetal weight were calculated-([larger twin-smaller twin]/larger twin)×100%-and compared between those with and without a large birthweight discordance (≥20%). Receiver operating characteristic curves were constructed to analyze the predictive characteristics of each parameter. Of 598 dichorionic twin pregnancies included, 83 (13.9%) had a birthweight discordance ≥20%. Group differences in biparietal diameter and head circumference discordance were the earliest to emerge (before 20weeks of gestation), but became insignificant after 36weeks, followed by humerus and femur length, estimated fetal weight discordance (after 20weeks), and abdominal circumference discordance (after 28weeks). The best predictors (with cut-off values) were discordance in biparietal diameter ≥7.8% at <20weeks, head circumference ≥4.5% at 20-23+6 weeks, humerus length ≥4.5% at 24-27+6 weeks, and estimated fetal weight discordance (≥11.6% at 28-31+6 weeks, ≥10.5% at 32-35+6 weeks, and ≥15.0% ≥36weeks), with sensitivity and specificity of 52%-77% and 69%-82%, respectively. Different predictors and cut-off values may be useful for predicting large inter-twin birthweight discordance in dichorionic twins at different gestational ages. It is more accurate to use biparietal diameter and head circumference discordance in the early second trimester, humerus length discordance in the late second trimester, and estimated fetal weight discordance in the third trimester.

Intra- and Inter-Group Differences in the Cognitive Skills of Toddler Twins with Birth Weight Discordance: The Need to Enhance Their Future from Early Education

Strengthening of early schooling enhances Equal and Inclusive Education (Sustainable Development Goal 4). Early education protects infant development and learning, especially for children suffering from pathologies and risk factors, such as twin birth weight discordance (BWD). These children—particularly the lighter twin—frequently show disadvantages in their cognitive skills. However, research about this issue is particularly scarce. The aims of this study were to (1) analyze the development of cognitive skills in each type of birth weight discordant twins (heavier and lighter ones) at 18, 21, and 24 months; and (2) discover whether there were differences between the two groups of twins in their cognitive skills. A nomothetic, follow-up, and multidimensional observational design was used. The cognitive skills of 32 birth weight discordant twins were observed while they played at 18, 21, and 24 months. The T-pattern analysis was performed using Thème software (Reykjavík, Iceland) to detect the sequential and temporal structure of infant behavior; indicative of cognitive skills. Results showed: (1) longitudinal intra-group differences in both groups of twins; and (2) some inter-group differences, mainly favoring the heavier twins. These results must be considered for designing early educational practices that allow all twins to be prepared for successful future learning.

Defining intertwin birth weight discordance and optimal delivery time in dichorionic twins: a retrospective cohort study

Background A high birth weight discordance (BWD) places twins at high risks of adverse perinatal outcomes; however, there is no commonly accepted definition of intertwin BWD. Given that gestational age (GA) is closely associated with both BWD and adverse neonatal outcomes, the aim of our study is to develop a measure that takes both BWD and GA into account to define BWD and explore the potentially optimal delivery time in dichorionic twins, with the balance against the risk of intrauterine demise and adverse neonatal outcomes. Methods About 99,000 mixed gender twin pairs from the US matched multiple birth file from 1995 to 2000 were enrolled in our study. We set up a two-dimensional matrix model to select the BWD cutoff point related to outcomes. The optimal delivery time was identified based on the risks of adverse neonatal outcomes and fetal death by GA. Results The combination of BWD and GA had a higher predictive performance for adverse neonatal outcomes than BWD alone (area under ROC curve (AUC): 0.816 vs. 0.523, p < .001). When GA was controlled for, the growth discordant cutoff point was BWD at the 40% level. The optimal delivery time suggested in dichorionic twins with BWD higher than 40% was identified at 33–34 gestational weeks. Conclusions The combination of BWD and GA was a better predictor for adverse neonatal outcomes than BWD alone. In dichorionic twins with BWD >40%, pregnancy may be continued till 33–34 gestation weeks if there is no indication for immediate delivery.

Distribution and Definition of Degree for Inter Twin Birth Weight Discordance

Distribution and Definition of Degree for Inter Twin Birth Weight Discordance

Neonatal outcomes between discordant monochorionic and dichorionic twins

Objectives This study aimed to compare obstetrical complications and neonatal outcomes between monochorionic and dichorionic discordant twin pregnancies. Study design We enrolled 296 patients with twin pregnancy who delivered at Busan Paik Hospital between January 2014 and December 2017. The prevalence of obstetrical complications, neonatal mortality between monochorionic and dichorionic twins was compared. We also investigated whether there is a difference in neonatal outcome and neonatal morbidity between monochorionic discordant twins without monochorionic-specific complications and dichorionic discordant twins. Results The risk of fetal death in utero (13.2 versus 5.2%, p = .025) and inter twin birth weight discordance (35.1 versus 20.8%, p = .031) is increased in monochorionic twins than in dichorionic twins. However, no difference was noted in obstetrical complication and neonatal mortality and morbidity between two groups. Among twin pregnancies with intertwin birth weight discordance, after excluding fetal death in utero and monochorionic specific complication, there was no difference in obstetrical complication and neonatal mortality and morbidity according to chorionicity. There was no difference in neonatal morbidity between monochorionic twins and dichorionic twins when comparing larger neonates and smaller neonates of each group. Conclusions Risk of birth weight discordance is higher in monochorionic twin but no significant difference was observed in maternal outcomes, neonatal mortality and morbidity between noncomplicated monochorionic and dichorionic discordant twins.

Intrauterine growth discordance across gestation and birthweight discordance in dichorionic twins

Although intertwin size difference is an important measure of fetal growth, the appropriate cut point to define discordance is unclear. Few studies have assessed intertwin differences in estimated fetal weight longitudinally or in relation to size differences at birth. The objectives of the study were to estimate the magnitude of percentage differences in estimated fetal weight across gestation in dichorionic twins in relation to a fixed discordance cut point and compare classification of aberrant fetal growth by different measures (estimated fetal weight differences, birthweight discordance, small for gestational age). Women aged 18-45 years from 8 US centers with dichorionic twin pregnancies at 8 weeks 0 days to 13 weeks 6 days gestation planning to deliver in participating hospitals were recruited into the Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies-Dichorionic Twins study and followed through delivery (n= 140; 2012-2013). Ultrasounds were conducted at 6 targeted study visits to obtain fetal biometrics and calculate estimated fetal weight. Percent estimated fetal weight and birthweight differences were calculated: ([weightlarger - weightsmaller]/weightlarger)*100; discordance was defined as ≥18% for illustration. Birth sizes for gestational age (both, 1, or neither small for gestational age) were determined; twins were categorized into combined birthweight plus small for gestational age groups: birthweight discordance ≥18% (yes, no) with both, 1, or neither small for gestational age. Linear mixed-models estimated percentiles of estimated fetal weight percent differences across gestation and compared estimated fetal weight differences between combined birthweight discordance and small for gestational age groups. A Fisher exact test compared birthweight discordance and small for gestational age classifications. Median estimated fetal weight percentage difference increased across gestation (5.9% at 15.0, 8.4% at 38.0 weeks), with greater disparities at higher percentiles (eg, 90th percentile: 15.6% at 15.0, 26.3% at 38.0 weeks). As gestation advanced, an increasing percentage of pregnancies were classified as discordant using a fixed cut point: 10% at 27.0, 15% at 34.0, and 20% at 38.0 weeks. Birthweight discordance and small for gestational age classifications differed (P= .002); for birthweight discordance ≥18% vs <18%: 44% vs 71% had neither small for gestational age; 56% vs 18% had 1 small for gestational age; no cases (0%) vs 11% had both small for gestational age, respectively. Estimated fetal weight percent difference varied across gestation by birthweight discordance plus small for gestational age classification (P= .040). Estimated fetal weight percentage difference increased with birthweight discordance ≥18% (neither small for gestational age: 0.46%/week [95% confidence interval, 0.08-0.84]; 1 small for gestational age: 0.57%/week [95% confidence interval, 0.25-0.90]) but less so without birthweight discordance (neither small for gestational age: 0.17%/week [95% confidence interval, 0.06-0.28]; 1 small for gestational age: 0.03%/week [95% confidence interval, -0.17 to 0.24]); both small for gestational age: 0.10%/week [95% confidence interval, -0.15 to 0.36]). The percentage of dichorionic pregnancies exceeding a fixed discordance cut point increased over gestation. A fixed cut point for defining twin discordance would identify an increasing percentage of twins as discordant as gestation advances. Small for gestational age and percentage weight differences assess distinct aspects of dichorionic twin growth. A percentile cut point may be more clinically useful for defining discordance, although further study is required to assess whether any specific percentile cut point correlates to adverse outcomes.

Association between the Degree of Twin Birthweight Discordance and Perinatal Outcomes.

Twin birthweight discordance is associated with adverse outcomes. To determine what degree of twin birthweight discordance is associated with adverse outcomes. This is a retrospective cohort study of twins with vertex twin A delivered vaginally at 36 to 40 weeks (U.S. Vital Statistics Natality birth certificate registry data 2012-2014). The primary outcome was a composite of neonatal morbidity: 5-minute Apgar < 7, neonatal intensive care unit admission, neonatal mechanical ventilation > 6 hours, neonatal seizure, and/or neonatal transport to a higher level of care. Effect estimates were expressed as incidence rate and adjusted odds ratio (aOR) controlling for confounding using multivariate clustered analysis for between-pair effects, and multilevel random effect generalized estimating equation regressions to account for within-pair effects. We adjusted for sex discordance, breech delivery of the second twin, maternal race/ethnicity, nulliparity, age, marital status, obesity, and socioeconomic status. In comparison to birthweight discordance of ≤20%, aORs with 95% confidence intervals (CIs) by weight discordance of the primary outcome among 27,276 twin deliveries were as follows: 20.01 to 25% (aOR: 1.46 [95% CI: 1.29-1.65]); 25.01 to 30% (aOR: 1.96 [95% CI: 1.68-2.29]); and 30.01 to 60% (aOR: 2.97 [95% CI: 2.52-3.50]). Twin birthweight discordance >20% was associated with increased odds of adverse neonatal outcome.

Prediction of birth weight discordance from fetal weight estimations at 21–24 weeks' scans in monochorionic and dichorionic twins

Objective: To evaluate if inter-twin estimated fetal weight (EFW) differences at 21–24 weeks’ scans predict birth weight discordance in monochorionic and dichorionic twins born at three gestational age periods.Methods: We counted the number of pairs with discordant EFWs (EFWs greater than the mean + 1SD; i.e. a difference above 12% in dichorionic and 21% in monochorionic twins) derived during a 21–24 weeks’ scan as compared to actual discordant birth weight (>25%) in monochorionic and dichorionic pairs born at ≤32, 33–36 and >36 weeks.Results: We studied 416 dichorionic and 244 monochorionic twins. The frequency of EFWs discordance at 21–24 weeks was the same for dichorionic and monochorionic twins but the total number of birth weight discordant pairs was significantly smaller among dichorionic twins (OR 0.2, 95% CI 0.1, 0.6). Generally, the positive predictive values for birth weight discordance by using the EFWs difference were quite poor, but always better in monochorionic than in dichorionic twins. Whereas the negative predictive value and hence the sensitivity for monochorionic twins was 100% irrespective of gestational age at birth, it was much lower in the dichorionic pairs.Conclusion: Concordant EFWs at 21–24 weeks exclude discordant birth weight in monochorionic twins whereas discordant EFWs are poor predictors of birth weight discordance especially in dichorionic twins irrespective when the twins were born.

Placental pathology in birth weight discordant monochorionic and dichorionic twins

Identification of placental parenchymal lesions (PPL) associated with birth weight (BW) discordance will be helpful in understanding the pathogenesis of BW discordance in twins. The aim of this study was to evaluate such association in monochorionic (MC) and dichorionic (DC) twins. This was a single centre, prospective study of placentas of consecutive twin deliveries. Gross and microscopic examination of placentas were done according to a protocol. Association of PPL count with the degree of BW discordance and the significance of the presence of each PPL in the lighter twin (LT) in comparison to the heavier twin (HT) were analysed. Of the 92 placentas studied 57.6% were DC and 42.4% were MC. Significant BW discordance was present in 28% (n=39) of MC and 26% (n=53) of DC twins. There was a positive correlation with the PPL count of the LT and the mean BW discordance in both MC (p=0.032) and DC twins (p=0.043). Increased incidence of distal villous hypoplasia in the placental territory of the LT in comparison to the HT was statistically significant in BW-discordant DC twins (P=0.04) and in both BW-concordant and BW-discordant MC twins (p=0.02 and p=0.03 respectively). In conclusion, this single centre prospective study showed a strong association between the PPL count and the degree of BW discordance in both MC and DC twins. Increased incidence of distal villous hypoplasia in the placental territory of the LT in comparison to the HT was statistically significant.

Gestational Age and Inter Twin Birth Weight Discordance in Korea; 2007-2014

Gestational Age and Inter Twin Birth Weight Discordance in Korea; 2007-2014

Differentially Methylated Genomic Regions in Birth-Weight Discordant Twin Pairs.

Poor nutrition during critical growth phases may alter the structural and physiologic development of vital organs thus "programming" the susceptibility to adult-onset diseases and disease-related health conditions. Epigenome-wide association studies have been performed in birth-weight discordant twin pairs to find evidence for such "programming" effects, but no significant results emerged. We further investigated this issue using a new computational approach: Instead of probing single genomic sites for significant alterations in epigenetic marks, we scan for differentially methylated genomic regions. Whole genome DNA methylation levels were measured in whole blood from 150 pairs of adult identical twins discordant for birth-weight. Intrapair differential DNA methylation was associated with qualitative (large or small) and quantitative (percentage) birth-weight discordance at each genomic site using regression models adjusting for age and sex. Based on the regression results, genomic regions with consistent alteration patterns of DNA methylation were located and tested for significant robustness using computational permutation tests. This yielded an interesting genomic region on chromosome 1, which is significantly differentially methylated for quantitative birth-weight discordance. The region covers two genes (TYW3 and CRYZ) both reportedly associated with metabolism. We conclude that prenatal conditions for birth-weight discordance may result in persistent epigenetic modifications potentially affecting even adult health.