First-born Twins Research Articles

Prevalence of respiratory distress syndrome in premature twins compared to premature singletons.

To estimate prevalence of respiratory distress syndrome in preterm twins compared to preterm singletons. This is a retrospective observational point prevalence study conducted at the level of three neonatal intensive care units. Medical records of all preterm newborns (<37 weeks of gestation) with respiratory distress syndrome treated in a two-year period were reviewed. The birth order of twins, gestational age and mortality were analysed. Out of 809 preterm newborns, 104 (12.9%) were twins. Median gestational age at birth was 30.3 (IQR 31.4-34.2) weeks. Respiratory distress syndrome was diagnosed in 525 (64.9 %) preterm newborns, of which 441 singletons and 84 twins. Prevalence of respiratory distress syndrome in first-born twins was not significantly higher compared with singletons, 67.3% (35/52) vs. 62.6 % (441/705), respectively (p=0.06). Prevalence of respiratory distress syndrome in second-born twins was 94.2 % (49/52), which was significantly higher compared with both singletons and first-born twins (p<0.001). The mortality rate of preterm newborns was significantly higher in second-born twins compared with singletons and first-born twins, 15.4 % vs. 6.8 % (p<0.001) and 15.4 % vs. 5.5% (p<0.001), respectively. There was a higher risk of respiratory distress syndrome and higher mortality rate in twins compared with singletons, but only in second-born twins the difference was statistically significant.

The Onset and Progression of Myopia Slows in Chinese 15-Year-Old Adolescents Following Vocational Rather Than Academic School Pathways.

The purpose of this study was to investigate the changes in spherical equivalent (SE) and axial length (AL) and cumulative incidence of myopia and high myopia in Chinese 15-year-old adolescents entering a non-academic stream of senior high school education. A total of 880 first-born twins with a baseline age range of 7 to 15 years were enrolled and followed annually until 18 years of age. Cycloplegic refractions and AL were examined. Educational exposure was divided into academic high school (AHS) and vocational high school (VHS) streams. A piecewise linear mixed-effects model was used to estimate the effect of education exposures on SE development, the slope before the age of 15 years (β2), and the slope change at the age of 15 years (β3) was compared between the 2 groups. The curves of refractive development in a myopic direction changed in parallel in the AHS and VHS group before 15 years. For nonmyopic children, β2 was -0.19 and -0.20 diopters (D)/year (P = 0.270), and β3 was 0.16 and 0.14 D/year (P = 0.270), in the AHS and VHS groups, respectively. Among patients with myopia, β2 was -0.52 and -0.54 D/year (P = 0.500), and β3 was 0.37 and 0.32 D/year (P = 0.004), in the AHS and VHS groups, respectively. The trends in AL were similar. The 3-year cumulative incidence of myopia was 35.3% (AHS) versus 14.7% (VHS; P < 0.001), and that of high myopia was 5.7% and 3.3% (P = 0.129). Students undertaking a VHS rather than an AHS education have slower myopic shifts in refraction and less incident myopia after the age of 15 years.

Second-versus first-born twin: comparison of short- and long-term outcomes.

An ancient description of the competition between twins for first breath is found in the biblical story of Jacob and Esau (Genesis 25:26) when Jacob pulled his older brother's heel in the hope of becoming firstborn but to no avail. In this study, we sought to evaluate the short and long-term outcomes of twin pairs, comparing between the second- and first-born twin. A population-based cohort study, including dichorionic twin deliveries occurring between the years 1991 and 2021 at Soroka University Medical Center. A General estimation equation (GEE) was applied to adjust for confounders. The incidence of offspring's hospitalizations due to various medical conditions was compared. Kaplan-Meier survival analyses compared cumulative morbidity. Cox proportional hazards models were used to control for confounders. 5507 twin deliveries met the inclusion criteria. Second-born twins had higher rates of cesarean deliveries, statistically significant in the GEE multivariable analysis. More first-twin fetuses were experiencing non-reassuring fetal heart rate patterns, although other obstetrical outcomes as well as mortality rates were comparable between groups. Second twins weighed lower than their older sibling (mean difference 33g) and were more frequently SGA and low birthweight (1500-2500g); (p < 0.05). Later during childhood, offspring of twin deliveries experienced notable morbidity due to infectious (23.8-24.1%), respiratory (10.5-10.9%), neurological (7.0-7.8%) and cardiovascular pathologies (1.7-1.9%) during childhood, that was unaffected by birth order. Other than birthweight differences, the birth order of dichorionic twins is not associated with adverse neonatal health indices, nor does it predict excess risk for morbidity during childhood.

Birthweight of the subsequent singleton pregnancy following a first twin or singleton pregnancy.

Birthweight is an important pregnancy indicator strongly associated with infant, child, and later adult life health. Previous studies have found that second-born babies are, on average, heavier than first-born babies, indicating an independent effect of parity on birthweight. Existing data are mostly based on singleton pregnancies and do not consider higher order pregnancies. We aimed to compare birthweight in singleton pregnancies following a first twin pregnancy relative to a first singleton pregnancy. This was a prospective registry-based cohort study using maternally linked offspring with first and subsequent pregnancies registered in the Medical Birth Registry of Norway between 1967 and 2020. We studied offspring birthweights of 778 975 women, of which 4849 had twins and 774 126 had singletons in their first pregnancy. Associations between twin or singleton status of the first pregnancy and birthweight (grams) in subsequent singleton pregnancies were evaluated by linear regression adjusted for maternal age at first delivery, year of first pregnancy, maternal education, and country of birth. We used plots to visualize the distribution of birthweight in the first and subsequent pregnancies. Mean combined birthweight of first-born twins was more than 1000 g larger than mean birthweight of first-born singletons. When comparing mean birthweight of a subsequent singleton baby following first-born twins with those following first-born singletons, the adjusted difference was just 21 g (95% confidence interval 5-37 g). Birthweights of the subsequent singleton baby were similar for women with a first twin or a first singleton pregnancy. Although first twin pregnancies contribute a greater combined total offspring birthweight including more extensive uterine expansion, this does not explain the general parity effect seen in birthweight. The physiological reasons for increased birthweight with parity remain to be established.

Hemoglobin differences in twins are related to the time of cord clamping, not intertwin transfusion – a prospective cohort study

BackgroundDelayed cord clamping increases placental transfusion. In vaginal deliveries higher hemoglobin concentrations are found in the second-born twin. We hypothesized it is unrelated to intertwin transfusion but to the time of cord clamping. Methods: It was a prospective cohort study of 202 women delivering twins > 32 weeks of gestation. Monoamniotic pregnancy, antenatal intertwin transfusions, fetal demise or major abnormalities were excluded from the study. The time of cord clamping depended on the obstetrician’s decision. Hemoglobin, hematocrit, and reticulocyte count were measured at birth and during the second day of life.ResultsAt birth, hemoglobin and hematocrit levels were significantly higher in the first-born twins delivered with delayed than with early cord clamping. Higher hemoglobin and hematocrit levels were observed during the second day of life in all twins delivered with delayed cord clamping. The lowest levels were observed in twins delivered with early cord clamping. Infants delivered with delayed cord clamping were at a lower risk of respiratory disorders and NICU hospitalization.ConclusionThe observed differences in Hgb concentrations between the infants in a twin pregnancy are related to cord clamping time.

Time trend analysis of perinatal mortality, stillbirth, and early neonatal mortality of multiple pregnancies for each gestational week from the year 2000 to 2019: A population-based study in Japan.

Multiple pregnancies pose a high risk of morbidity and mortality in both mothers and infants; thus, obtaining reliable information based on a large population is essential to improve management. We used the maternal and child health statistics, which are published annually, from the database of the Ministry of Health, Labor, and Welfare. The data obtained were aggregated in 5-year intervals, and we used them to analyze the proportion of the number of births for each week of pregnancy to the total of each singleton and multiple pregnancy. For perinatal health indicators (perinatal mortality, stillbirth, and neonatal mortality), the obtained data were calculated and plotted on graphs for each week of pregnancy. Moreover, these indicators were calculated by dividing them into first twin and second twin fetuses. Stillbirth weights were aggregated in several groups, and a histogram was displayed. Between 2000 and 2019, there were 21,068,275 live births, 67,666 stillbirths, and 16,443 early neonatal deaths, excluding 7,148 (7,104 singletons, 44 multiple births) cases, in which the exact gestational weeks at birth were unknown. More than 95% of multiple pregnancies were twin births. Perinatal mortality, stillbirth, and early neonatal mortality rates in multiple pregnancies were the lowest at approximately 37 weeks of gestation and lower than those of single pregnancies at approximately 36 weeks of gestation. Perinatal mortality and stillbirth rates were higher during the delivery of the second twins than the first-born twins, but the early neonatal mortality rate remained approximately the same during the delivery of both twins. As the data in the government database are accumulated and published continuously, indicators can be calculated in the future using the method presented in this study. Further, our findings may be useful for policymaking related to managing multiple pregnancies.

Second versus Firstborn Twin: Comparison of Long-term Outcomes

Twins are considered high-risk pregnancies owing to increased risk of complications and mainly preterm birth. Lower birthweight and other obstetrical issues unique to second-born twins may put them at even higher risk of adverse neonatal outcomes. Scarce data exists regarding the long-term health outcomes of twin pairs, stratified for birth order. Thus, we sought to determine whether twins born second are at an increased risk for long-term morbidity.

A descriptive analysis on body mass index distribution in adult twin pairs in China

Objective: To describe the differences in body mass index (BMI) distribution in adult twins registered in Chinese National Twin Registry (CNTR), and provide evidence for the risk factor analysis and prevention and control of overweight or obesity. Methods: A total of 32 725 twin pairs aged 18 years and above who completed the questionnaire survey during 2010-2018 and had complete registered information in CNTR and normal body weight and length were included in the analysis on the population and region specific distributions of BMI of twin pairs and the difference in BMI in twin pairs. Results: The twin pairs included in the analysis were aged (34.6±12.4) years, the twin pairs of same gender accounted for 79.7%. The average BMI was 22.5 kg/m2. The overall prevalence of obesity and overweight was 4.9% and 23.7%, respectively. Participants who were men, 50-59 years old, married, had lower education level, and lived in northern China had higher overweight rate and obesity rate (P<0.001). The difference in overweight or obesity prevalence between monozygotic (MZ) twin pars and dizygotic (DZ) twin pairs was not significant, but firstborn twin pairs had slightly higher rates of overweight and obesity than later-born twin pairs (P<0.05). The analysis in same gender-twin pairs indicated that the difference in BMI was associated with age (trend test: P<0.001), and the difference was more obvious in DZ twin pair in MZ pair and this difference increased with age. The concordant rate of BMI was higher in MZ twin pairs than DZ twin pairs (P<0.05). Conclusion: The distribution of BMI of twin pairs varied with population and region and BMI varied with age due to its genetic nature.

Supplementing Merino ewes with melatonin during the last half of pregnancy improves tolerance of prolonged parturition and survival of second-born twin lambs.

High preweaning mortality rates continue to limit sheep production globally, constituting a major economic and welfare concern. Greater losses in twin lambs (≥30%) compared with singletons (≥10%) are attributed primarily to lower birth weight and increased risk of intrapartum hypoxia, leading to impairment of thermoregulation, neuromotor activity, and maternal bonding behavior. Previous intensive studies demonstrated that supplementing pregnant ewes with melatonin reduced the adverse effects of fetal growth restriction and perinatal hypoxia on the neonatal brain via increased umbilical blood flow, placental efficiency, and antioxidant actions. The current study examined the effects of supplementing pregnant ewes with melatonin on lamb survival, birth weight, and behavior under intensive conditions. From gestational day (gD) 80 until parturition, pregnant singleton and twin-bearing ewes were supplemented with melatonin via a 2-mg capsule fed daily (Mel-FED, n = 61) or 18 mg subcutaneous implant (Regulin), with one implant administered at gD80 and another at gD125 (Mel-IMP, n = 60). Control ewes received no supplementation (CTL, n = 60). Ewes and lambs were monitored via video throughout parturition. Postpartum measures were taken from lambs at 4 and 24 h (live weight [LW], rectal temperature, serum immunoglobulin G, and latency to stand and suck after birth) and LW at 72 h, 7 d, marking (49.7 ± 0.2 d), and weaning (124.2 ± 0.8 d). Chi-square analysis was used to compare lamb survival between treatment groups. There were no treatment effects on singleton lamb survival. Melatonin supplementation tended to increase the proportion of twin lambs surviving from birth to weaning (Mel-FED = 85.5%; Mel-IMP = 85.9%; CTL = 72.9%; each P < 0.1). Survival of first-born twins did not differ between treatment (each ~90%, P = 0.745) but within second-born twins, survival of Mel-FED was greater than CTL (81.6 vs. 57.1%, P = 0.023), and Mel-IMP (78.1%) tended to be greater than CTL (P = 0.068). Similarly, in second-born twins exposed to prolonged parturition (≥ 90 min), survival of lambs from Mel-FED ewes was greater than CTL (86.7% vs. 42.9%, P = 0.032), while Mel-IMP was intermediate (66.7%). These data suggest that the neuroprotective actions of melatonin may improve twin lamb survival by increasing tolerance of prolonged parturition and provide a sound basis for continued testing in extensively managed sheep flocks.

Christopher Michael Taylor

Christopher Michael Taylor (“Chris”) was born in Bowden, Lancashire on 27 July 1952. He was the first-born twin, and his sister followed minutes later—much to the surprise and shock of...

Eye Discharge in a 9-day-old Twin Boy.

1. Eleanor A. Sharp, MD* 2. Jessica L. Garrison, MD* 1. *Paul C. Gaffney Division of Pediatric Hospital Medicine, UPMC Children’s Hospital of Pittsburgh, Pittsburgh, PA A 9-day-old infant boy presents to the emergency department with a 1-day history of bilateral eye redness and yellow discharge. The morning before presentation, his mother noted his right eye to be crusted shut with dried yellow discharge. She applied a warm compress that removed the discharge and allowed him to open his eye normally. However, over the next several hours he developed bilateral eyelid swelling and yellow drainage from both eyes. He seemed to be trying to rub his eyes and was fussier than usual. The day of presentation, his mother noted both his eyes were red, swollen, and draining yellow fluid, so she brought him to the emergency department for evaluation. The patient has not been breastfeeding as long or as frequently as usual over the past day but has still had normal stool and urine output. The patient has not had fever, nasal congestion, rhinorrhea, rash, or sick contacts. His twin sister is asymptomatic. The patient was born full term via spontaneous vaginal delivery. He was the firstborn twin. The mother received routine prenatal care, and both the pregnancy and delivery were uncomplicated. Maternal screening for gonorrhea and chlamydia at the first prenatal visit was negative, and the patient received ophthalmic erythromycin after delivery. In the emergency department, the infant is afebrile with normal vital signs for age. He is fussy but consolable. He has periorbital swelling with overlying erythema, conjunctival injection, and mucopurulent discharge from both eyes, right worse than left. The reminder of his examination is unremarkable. Due to his age, evaluation for possible serious bacterial infection is completed. His white blood cell count is …

Association of Age at Myopia Onset With Risk of High Myopia in Adulthood in a 12-Year Follow-up of a Chinese Cohort

Early-onset myopia is well known to progress to high myopia in adulthood. However, no accurate estimation of how a specific age at myopia onset is associated with the probability of developing high myopia in adulthood is available, and a very-long-term follow-up study with data from annual visits is needed. To estimate the risk of developing high myopia in adulthood associated with a specific age at myopia onset from a data set with a 12-year annual follow-up. This ongoing, population-based prospective cohort study of twins was conducted in Guangzhou, China, on July 11, 2006. Data from baseline to August 31, 2018, were analyzed. The first-born twins completed follow-up until 17 years or older, and the 443 participants (after exclusions) who developed myopia were included in the analysis. Data were analyzed from September 1, 2018, to January 20, 2020. Age at myopia onset was determined by prospective annual cycloplegic refractions (365 participants [82.4%]) or with a questionnaire. Refraction in adulthood was defined as the cycloplegic refraction measured at the last follow-up visit. Among the 443 eligible participants (247 [55.8%] female; mean [SD] age at myopia onset, 11.7 [2.0] years), 54 (12.2%) developed high myopia (spherical equivalent, -6.00 diopters or worse determined by cycloplegic refractions) in adulthood. Among participants with age at myopia onset of 7 or 8 years, 14 of 26 (53.9%; 95% CI, 33.4%-73.4%) developed high myopia in adulthood; among those with onset at 9 years of age, 12 of 37 (32.4%; 95% CI, 18.0%-49.8%); among those with onset at 10 years of age, 14 of 72 (19.4%; 95% CI, 11.1%-30.5%); among those with onset at 11 years of age, 11 of 78 (14.1%; 95% CI, 7.3%-23.8%); and among those with onset at 12 years or older, 3 of 230 (1.3%; 95% CI, 0.2%-3.8%). Results of multivariate logistic regression analysis suggested that the risk of developing high myopia in adulthood decreased significantly with delay in the age at myopia onset (odds ratio, 0.44; 95% CI, 0.36-0.55; P < .001), from greater than 50% for 7 or 8 years of age to approximately 30% for 9 years of age and 20% for 10 years of age. These findings suggest that the risk of high myopia is relatively high in children with myopia onset during the early school ages. Each year of delay in the age at onset substantially reduces the chance of developing high myopia in adulthood, highlighting the importance of identifying effective prevention strategies under investigation, such as increasing outdoor time.

Речевое взаимодействие в триадах «мать—дизиготные близнецы» в 4—6-летнем возрасте детей

The longitudinal study of mother speech interaction with 4-6-years-old dizygotic twins (n=5 triads) was performed. The characteristics of maternal speech addressed to twins, characteristics of children’ speech development due to the order of the birth are investigated. The first-born child in pair have a higher level of speech development as compared to the second-born child by syntactic structure of sentences in dialogue, number of consonants, meanings of pitch in vowels. Correlation between characteristics of maternal speech and the level of twin’s speech development is revealed. When mothers interact with the second-born twins they stimulate them to communication more then the first-born twins.

Modeling perinatal mortality in twins via generalized additive mixed models: a comparison of estimation approaches

BackgroundThe analysis of twin data presents a unique challenge. Second-born twins on average weigh less than first-born twins and have an elevated risk of perinatal mortality. It is not clear whether the risk difference depends on birth order or their relative birth weight. This study evaluates the association between birth order and perinatal mortality by birth order-specific weight difference in twin pregnancies.MethodsWe adopt generalized additive mixed models (GAMMs) which are a flexible version of generalized linear mixed models (GLMMs), to model the association. Estimation of such models for correlated binary data is challenging. We compare both Bayesian and likelihood-based approaches for estimating GAMMs via simulation. We apply the methods to the US matched multiple birth data to evaluate the association between twins’ birth order and perinatal mortality.ResultsPerinatal mortality depends on both birth order and relative birthweight. Simulation results suggest that the Bayesian method with half-Cauchy priors for variance components performs well in estimating all components of the GAMM. The Bayesian results were sensitive to prior specifications.ConclusionWe adopted a flexible statistical model, GAMM, to precisely estimate the perinatal mortality risk differences between first- and second-born twins whereby birthweight and gestational age are nonparametrically modelled to explicitly adjust for their effects. The risk of perinatal mortality in twins was found to depend on both birth order and relative birthweight. We demonstrated that the Bayesian method estimated the GAMM model components more reliably than the frequentist approaches.

Contribution of Genome-Wide Significant Single Nucleotide Polymorphisms in Myopia Prediction: Findings from a 10-year Cohort of Chinese Twin Children

To determine the added predictive ability of genome-wide significant single nucleotide polymorphisms (SNPs) in refraction prediction in children and investigate the earliest age threshold for an accurate prediction of high myopia. Prospective longitudinal study. A total of 1063 first-born twins followed annually between 2006 and 2015 in China. The exposures were genetic factors (parental myopia, SNPs) and environmental factors (near work, outdoor activity). Five linear mixed-effect models, consisting of different combinations of age, gender, genetic, and environmental factors, were built to predict myopia development. All predictions were performed on the basis of spherical equivalent (SE) at baseline and the measurements on the second and third visits. The primary outcome measure was SE at the last visit among all subjects, and the secondary outcome measure was the presence of high myopia at the age of 18 years. Mean age of the study population was 10.5±2.2 years (range, 7-15 years) at baseline, and 48.6% were male. In linear mixed-effect models, age, age square, gender, paternal SE, maternal SE, and genetic risk scores (GRSs) showed a significant fixed effect, whereas outdoor and near-work time were not significant to SE at the last visit. Incorporating more follow-up data into the model showed better performance across all models. In the prediction of the presence of high myopia at 18 years of age, the model consisting of only age and gender showed a good performance (area under the curve [AUC]= 0.95), whereas the addition of SNPs did not enhance the model performance significantly. The AUC for predicting high myopia was >0.95 after the age of 13 years for participants with a single visit and after the age of 12 years for those with 1 more visit data. A simple model incorporating age, sex, and relevant refraction data is sufficient to accurately predict high myopia; there was limited improvement in the prediction model after adding genetic information. Furthermore, this prediction on the outcome at 18 years is possible when the child is aged 12 to 13 years.

Pre- and Perinatal Characteristics Associated with Apgar Scores in a Review and in a New Study of Dutch Twins.

A literature review was carried out to identify pre and perinatal characteristics associated with variation in Apgar scores in population-based studies. The parameters identified in the literature search were included in the classical twin design study to estimate effects of pre and perinatal factors shared and nonshared by twins and to test for a contribution of genetic factors in 1- and 5-min Apgar scores in a large sample of Dutch monozygotic (MZ) and dizygotic (DZ) twins. The sample included MZ and DZ twins (N = 5181 pairs) recruited by the Netherlands Twin Register shortly after birth, with data on prenatal characteristics and Apgar scores at first and/or fifth minutes. The ordinal regression and structural equation modeling were used to analyze the effects of characteristics identified in the literature review and to estimate genetic and nongenetic variance components. The literature review identified 63 papers. Consistent with the review, we observed statistically significant effects of birth order, zygosity and gestational age (GA) for 1- and 5-min Apgar scores of both twins. Apgar scores are higher in first-born versus second-born twins and DZ first-born versus MZ first-born twins. Birth weight had an effect on the 5-min Apgar of the first born. Fetal presentation and mode of delivery had different effects on Apgar scores of first- and second-born twins. Parental characteristics and chorionicity did not have significant main effects on Apgar scores. The MZ twins' Apgar correlations equaled the DZ Apgar correlations. Our analyses suggest that individual differences in 1- and 5-min Apgar scores are attributable to shared and nonshared pre and perinatal factors, but not to genotypic factors of the newborns. The main predictors of Apgar scores are birth order, zygosity, GA, birth weight, mode of delivery and fetal presentation.

723: Differences in long-term morbidities between the first and the second born twins.

Recent studies have reported an increased risk of short-term neonatal morbidity among second versus first-born twins in term and late preterm twin populations. The present study was aimed to investigate whether the second twins are also at an increased risk for long-term pediatric morbidity. In this population-based retrospective cohort study, the incidence of long-term (up to the age of 18 years) hospitalizations due to cardiovascular, neurological, respiratory, and infectious pediatric morbidities was investigated. A comparison was performed between the first and second born diamniotic twins. Deliveries occurred between the years 1991 and 2014 in a tertiary referral hospital. The risk for long-term morbidities in the twins was based on the hospital’s pediatric database and a pre-defined set of ICD-9 codes. Kaplan-Meier survival curves were constructed to compare cumulative morbidities and Cox proportional hazards models were used to control for confounders. In the current study 1919 sets of twins were inclucded. The total long-term hospitalizations, up to 18 years of age, due to cardiovascular (0.8% vs 0.6%, P=0.18), respiratory (4.0% vs 3.7%, P=0.29), neurologic (3.2% vs 3.6%, P=0.31) and infectious hospitalizations (7.5%% vs 7.5%, P=0.13) were comparable between the first and the second born twins (Table). Likewise, the Kaplan-Meier survival curves showed no difference in the cumulative incidence of total cardiovascular, respiratory, neurologic or infectious long-term hospitalizations between first and second born twins (Figure). In the Cox regression models adjusting for mode of delivery and gestational age, adjuted hazards ratios (aHR) were comparable between first and second born twin regarding cardiovascular (aHR=0.89, 95% CI 0.76-1.05, P=0.18), respiratory (aHR=1.01, 95% CI 0.94-1.06, P=0.91), neurological (aHR=1.21, 95% CI 0.84-1.74, P=0.30) or infectious morbidities (aHR=1.08, 95% CI 0.97-1.20, P=0.13). The second-born twin does not seem to be at an increased risk for long-term pediatric morbidity. Cumulative incidence of hospitalizations up to 18 years of age due to cardiovascular, neurological, respiratory, and infectious pediatric morbidities is comparable between the first and second born twin.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

143: Neonatal outcome- second-born vs first-born twin at late-preterm: Does it depend on the delivery mode

143: Neonatal outcome- second-born vs first-born twin at late-preterm: Does it depend on the delivery mode

The effects of birth order on neonatal outcomes in early-preterm, late-preterm and term twin infants*

Objectives: Birth order is one of the main factors that influences the neonatal outcome of twins. However, there is little prior data regarding the effect of birth order under different clinical circumstances. This study investigates the effect of birth order on the neonatal outcomes of twins delivered during early-preterm, late-preterm and term gestations according to chorionicity, delivery mode and indication for delivery.Methods: This is a retrospective cohort study of women with twin pregnancies delivered at 24–40 weeks of gestation between 1995 and 2014. We excluded twin pregnancies with the following complications: twin-to-twin transfusion syndrome, monoamnionic twins, delayed interval delivery and fetal death, chromosomal anomalies or major congenital malformation in one or more of the twins. The neonatal outcomes, including death, admission to neonatal intensive care unit (NICU), mechanical ventilator support, and respiratory distress syndrome (RDS) was compared between the first and second twin born at early-preterm (24–33 weeks of gestation), late-preterm (34–36 weeks of gestation) and term (≥37 weeks of gestation) gestations. These outcomes were further analyzed according to chorionicity, mode of delivery and indication for delivery by multivariable analysis (after adjusting for sex, presentation, and birth weight).Results: Among a total of 1,614 women with twin pregnancies who met the selection criteria, 423, 674 and 517 women delivered at early-preterm, late-preterm and term gestation, respectively. Overall, the second-born twins were lighter and had higher rates of NICU admission, mechanical ventilator support, and RDS than did first-born twins. Second twins born at early-preterm gestation had higher rates of RDS and mechanical ventilator support than did first twins. Second twins born at late-preterm gestation had higher rates of NICU admission and mechanical ventilator support than did first twins. Second twins born at term gestation also had a higher NICU admission rate than did first twins. However, in the multivariable analysis of the subgroups, the rates of NICU admission, mechanical ventilator support and RDS were not significantly different between most twin pairs. However, there were several significant differences. There was a higher risk of RDS in the second twins in the early-preterm premature rupture of membranes (PROM) subgroup, and a higher risk of mechanical ventilator support in the late-preterm PROM subgroup. Low birth weight was the only significant factor independently associated with a higher risk of adverse neonatal outcome in the second twins compared with the first twins in all subgroups.Conclusions: Second twins born at early-preterm, late-preterm and term were at higher risk of adverse neonatal outcome than were their respective first twins. However, this finding was mainly represented lower birth weight of the second twin. Still, second twins delivered due to early-preterm and late-preterm PROM had a higher risk of RDS and mechanical ventilator support, respectively, than did the first twin after adjusting for birth weight.

Relations of laterality and chewing sidedness in twins.

To study, whether there are associations between chewing side preference and other lateralities, whether there is a genetic origin for preferred chewing side (PCS), relations to sex, birth order and orthodontic treatment. The study included 113 twin pairs, 57 pairs monozygotic, 47 pairs same sex dizygotic and 9 pairs of opposite sex. The lateralities of preferred chewing side, footedness and eyedness were assessed by functional tests and handedness was checked by asking. Right-handed, -footed and -eyed as separated groups, and true-right sided (combined), were evenly distributed by preferred chewing side. By contrast, left-handed, -footed, -eyed and non-right sided used more left or both sides when chewing. Birth order affected preferred chewing side among monozygotic: the first-born twin was more likely to have the preferred chewing side on the non-right, whereas second-born twins used right side. Gender, zygosity and orthodontic treatment were not statistically significant factors. Examination of chewing sidedness could have been done in several different ways to provide a definite result. Sample size of opposite sex twins was very small. Preferred chewing side generally seemed to follow the side where other lateralities occur; however, monozygotic twins seemed to be more receptive to it. True-right sided were more evenly distributed than non-right sided by the preferred chewing side.