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At least 163 records · Page 9Linked to original sources
PubMed2005

[Analysis of the efficacy of Twin-block appliance on maxillofacial growth of six pairs of monozygotic twins].

PURPOSE: The purpose of this study was to investigate the efficacy of Twin-block appliance on maxillofacial growth by using monozygotic twins. METHODS: 6 pairs of non-high angle monozygotic twins aged 12.2 with class II division 1 malocclusion were selected from 32 pairs of twins. In the first year Twin A of each pair was functionally treated using Twin-block appliance; meanwhile, Twin B underwent non-extracted fixed treatment without any treatment procedure which might cause changes like functional appliances such as Class II elastics. The difference of the cephalometric changes of maxilla and mandible before and after treatment between Twin A and Twin B was compared using paired-t test. RESULTS: Compared with those of Twin A after one year treatment, SNA, Cd-A and Cd-Go of Twin B had little chang (P>0.05), but Cd-S' reduced (P<0.05), Cd-Gn and SNB increased (P=0.01), (Cd-Gn)-(Cd-A) and ANB increased (P<0.05) significantly. CONCLUSION: Twin-block appliance can stimulate forward mandibular growth and cause forward mandibular displacement, but has little effect on ramus height and maxillary growth.

Cephalometry↗
PubMed2005

Monochorionic diamniotic infants without twin-to-twin transfusion syndrome.

BACKGROUND: Monochorionic-diamniotic twins (MoDi) occur in 0.3% of all pregnancies. Twin-to-twin transfusion syndrome (TTS) that occurs in 20% of MoDi pregnancies is associated with high perinatal morbidity and mortality. MoDi twins without TTS are more frequent (80%) but have been scarcely reported. OBJECTIVE: To study perinatal morbidity and mortality of 74 MoDi twin sets without TTS and to compare it to that of 38 sets of MoDi twins with TTS. METHODS: Chorionicity was determined by gender and placental examination. Gestational age (GA) was set by sonography and pediatric examination. TTS was diagnosed clinically and by sonography, discordance was defined by twins birth weight difference > or =20%, and fetal growth restriction was determined by using a twin-specific nomogram. RESULTS: MoDi twin pregnancies without and with TTS were similar in demographics, live births, history of preeclampsia, fetal distress and cesarean delivery. They were different (p<0.01) in discordant pregnancies (36 and 79%), GA at delivery (32 and 29 weeks) intrauterine growth restriction (39 and 89%) and neonatal mortality (12 and 36%). Concordant (47 sets) and discordant (27 sets) MoDi twins without TTS were clinically similar. CONCLUSIONS: MoDi twins without TTS have high rates of birth weight discordance, fetal growth restriction, fetal distress, prematurity and cesarean delivery. Although their perinatal mortality is low, the reported occurrence and the short- and long-term impacts of fetal and neonatal morbidities warrants attention.

Amnion↗
PubMed2001

The influence of zygosity and chorion type on fat distribution in young adult twins consequences for twin studies.

An adverse intra-uterine environment has been associated with abdominal fat distribution in singletons. Twins often have a low birth weight and a short gestation. Therefore, they may have an increased risk to develop abdominal obesity. Furthermore, monozygotic monochorionic twins (MZ MC) have a larger intra-pair birth weight difference compared to monozygotic dichorionic twins (MZ DC). If adult anthropometry is programmed in utero, this may affect the intra-pair correlations in adulthood and, consequently, also the results from the classic twin method to estimate genetic and environmental influences. In the present study, we compared the absolute values, the intra-pair differences, and the intra-pair correlations of body mass, height, BMI, and abdominal fat distribution of 424 MZ MC, MZ DC and dizygotic (DZ) twin pairs (aged 18-34 yrs). DZ, MZ DC and MZ MC twins did not differ for most anthropometric characteristics. Only MZ women tended (p = 0.03) to accumulate more abdominal fat compared to DZ twins. Overall, the contribution of zygosity and chorion type to adult anthropometry was rather low (< or = 1.7%). Although the intra-pair birth weight difference of MZ MC pairs (10.5% in men, 12.3% in women) was significantly larger compared to that of MZ DC pairs (6.9% and 9.2% resp.), the intra-pair differences in adult anthropometry were similar for both MZ twin types. Also the intra-pair correlations of MZ MC and MZ DC pairs were strikingly alike, suggesting no significant influence of the prenatal environment on adult concordance. In conclusion, the substantial difference in the prenatal environment of MZ MC and MZ DC twins did not result in a difference in intra-pair concordance of adult anthropometry and fat distribution. Therefore, we suggest that the chorion type of MZ twins does not bias the twin design and the estimation of the genetic contribution to adult anthropometry.

Adipose Tissue↗
PubMed1995

Comparison of intrauterine hematologic and biochemical values between twin pairs with and without stuck twin syndrome.

OBJECTIVE: Our purpose was to compare hematologic and biochemical values in cordocentesis specimens from twin pairs with and without stuck twin syndrome. STUDY DESIGN: Cordocentesis was performed on 38 twin pairs. Assignment to the stuck twin syndrome group (n = 8) was based on ultrasonographic findings of discordant size and amniotic fluid volume, concordant gender, and a single placenta. A receiver-operator characteristic curve was constructed with the use of intertwin hemoglobin differences. For the stuck twin syndrome group regression analysis of gestational age and intertwin hemoglobin difference was done. RESULTS: We found significant (p = 0.03) intertwin differences in hemoglobin between the stuck twin syndrome group (mean 5.35 gm/dl, range 0.5 to 15.4 gm/dl) and the comparison group (mean 0.10 gm/dl, range 0.0 to 2.4 gm/dl). A nearly significant relationship between gestational age and intertwin hemoglobin difference was noted in the stuck twin syndrome group. When the hemoglobin difference was > 2.4 gm/dl, all cases had stuck twin syndrome (sensitivity = 50%, specificity = 100%, positive predictive value = 100%, negative predictive value = 91%). In the stuck twin syndrome group there was a trend toward larger intertwin differences in albumin and total protein. Intertwin blood gas values between the groups did not differ, but the average PO2 was lower when the smaller twins of the two groups were compared. CONCLUSION: An intertwin difference in hemoglobin > 2.4 gm/dl is consistent with stuck twin syndrome. Large intertwin hemoglobin differences and imbalances in albumin and total protein may be seen in stuck twin syndrome.

Blood Chemical Analysis↗
PubMed1990

Interval between birth of the first and the second twin and its impact on second twin perinatal mortality.

We investigated the impact of a long interval between the birth of the first and the second twin on second twin perinatal mortality (PNM). National data in the Swedish Medical Birth Registry were used on 7533 second twins born in Sweden between 1973 and 1985. PNM as a function of the time interval between the births of the twins was studied in data from two time periods: during 1973-78 (n = 4008) and 1979-85 (n = 3525). During the first period, PNM was significantly higher at intervals of 30 min or more between the births of the twins than at shorter intervals (chi 2 = 11.1, p less than 0.001). When studied within broad birth weight classes, a significant trend was seen for twins weighing 1500-2499 g with an increasing interval (chi 2 = 8.1: p less than 0.01). A non-significant trend was also found for twins weighing less than 1500 g but none for twins weighing greater than or equal to 2500 g. During the second period, abdominal delivery of the second twin after vaginal delivery of the first twin was significantly more common than during the first period (2.0% vs 0.3%, chi 2 = 52.7, p less than 0.001). During the second period, the interdelivery interval had little impact on second twin PNM. The results of this study seem to indicate that with modern management of labor and delivery, as seen in Sweden since 1979, the interdelivery interval has little impact on second twin PNM.

Cesarean Section↗
PubMed1997

Genetic and environmental parameters for ovulation rate, twinning rate, and weight traits in a cattle population selected for twinning.

A project was implemented in 1981 with the objective of increasing twinning rate in cattle. Daughters of foundation sires had twin calves at a frequency of from 8 to 13%, and foundation females had twin calves at an average frequency of 50%. Data were analyzed on twinning rate, ovulation rate, and weight traits. The h2 of ovulation rate increased from .11 to .38 for a single estrous cycle to the mean of eight estrous cycles. From all data, h2 for single observation of ovulation rate and twinning rate were .10 and .09, respectively. The r(g) between them was .75. The h2 of weight traits ranged from .42 to .54 when weight traits were analyzed pair-wise with ovulation rate and with twinning rate. The r(g) between weight traits with ovulation rate ranged from .15 to .30 and with twinning rate ranged from .24 to .39. Phenotypic mean twinning rate increased from 1.07 to 1.29 calves per parturition for females born 1981 through 1993, and adjusted mean predicted breeding value (PBV) increased from 1.07 to 1.33 calves per parturition. Phenotypic mean ovulation rate for fall of 1984 through fall 1994 birth groups increased from 1.11 to 1.26 per estrous cycle, and adjusted mean PBV for ovulation rate increased from 1.11 to 1.29 per estrous cycle. Because of the high r(g) (i.e., .75) between ovulation rate and twinning rate, and because of a h2 of .35 for ovulation rate for the mean of six estrous cycles, repeated records of ovulation rate in puberal heifers is an effective indirect selection criterion for twinning rate. The positive r(g) between growth traits and ovulation and twinning rate suggest the need for some compromise when the selection goal is increased twinning rate with no increase in growth and size.

Animals↗
PubMed1994

[Analysis of 122 twin deliveries with special reference to morbidity and mortality of the second twin].

122 consecutive twin deliveries between 1986-1992 were analysed retrospectively under special consideration of morbidity and mortality of the second twin. 13.9% of the twin deliveries occurred before the 33rd week of gestation. The cesarean section rate amounted to 49.2%, the first twin was delivered in 5.7%, the second twin in 27%, by vaginal operative methods. Perinatal mortality of the first twin was 3.3%, of the second twin 6.6% (p < 0.01); thus resulting in an overall twin mortality rate of 4.9%. The acidosis-rate of 16.4% in the second twin was significantly above the 9.0% in the first twin. The vaginal operative mode delivery especially contributed to the impaired outcome of the second twin. There was no correlation between the morbidity of the second twin and the time interval between the two deliveries.

Adolescent↗
PubMed1993

The role of velamentous cord insertion in the etiology of twin-twin transfusion syndrome.

OBJECTIVE: To evaluate the prevalence of velamentous cord insertion in twin-twin transfusion using the hypothesis that such insertions may contribute to the etiology of the condition. METHODS: All cases of placentas referred for pathologic evaluation at the University of California at San Francisco from 1984-1992 were reviewed for the citation of diamniotic-monochorionic placentation, including the presence of velamentous cord insertions. Maternal and infant records were studied for findings consistent with twin-twin transfusion syndrome. RESULTS: Thirty-eight cases of monochorionic-diamniotic twins were identified, 11 of which showed twin-twin transfusion syndrome. The prevalence of velamentous cord insertion in the transfusion syndrome subset was 63.6%, compared with 18.5% in those without (significant difference at P < .01). Twin-twin transfusion syndrome pregnancies with velamentous insertions were delivered at a significantly earlier gestational age; they also had fewer surviving infants and were more likely to have been treated prenatally than transfusion syndrome pregnancies without velamentous insertion, although these latter two findings were not significantly different. CONCLUSIONS: Velamentous cord insertions are more common in twin-twin transfusion syndrome pregnancies and may contribute to the development of profound disparity in fluid volume because the membranously inserted cord can be easily compressed, reducing blood flow to one twin. Large-volume amniocentesis may reduce this compressive force on the cord insertion, thus explaining the success of this mode of intervention.

Female↗
PubMed2004

Haemodynamic resistance model of monochorionic twin pregnancies complicated by acardiac twinning.

An acardiac twin is a severely malformed monochorionic twin fetus that lacks most organs, particularly a heart. It grows during pregnancy, because it is perfused by its developmentally normal co-twin (called the pump twin) via a set of placental arterioarterial and venovenous anastomoses. The pump twin dies intrauterine or neonatally in about 50% of the cases due to congestive heart failure, polyhydramnios and prematurity. Because the pathophysiology of this pregnancy is currently incompletely understood, we modified our previous haemodynamic model of monochorionic twins connected by placental vascular anastomoses to include the analysis of acardiac twin pregnancies. We incorporated the fetoplacental circulation as a resistance circuit and used the fetal umbilical flow that perfuses the body to define fetal growth, rather than the placental flow as done previously. Using this modified model, we predicted that the pump twin has excess blood volume and increased mean arterial blood pressure compared to those in the acardiac twin. Placental perfusion of the acardiac twin is significantly reduced compared to normal, as a consequence of an increased venous pressure, possibly implying reduced acardiac placental growth. In conclusion, the haemodynamic analysis may contribute to an increased knowledge of the pathophysiologic consequences of an acardiac body mass for the pump twin.

Biophysics↗
PubMed2001

Does higher concordance in monozygotic twins than in dizygotic twins suggest a genetic component?

It is widely regarded that twins can be used as a natural experiment to subject hypotheses to empirical testing regarding the contributions of genetic factors to phenotypic variability in human traits, especially behavioral traits. In genetic epidemiology, a higher concordance rate in monozygotic (MZ) twins than in dizygotic (DZ) twins is often taken as prima facie evidence for a genetic component. While twins studies have been used to estimate the contributions of genetic factors to phenotypic variability in human traits, the corresponding methodology that allows the estimation entails several crucial assumptions. The most critical is that MZ and DZ twins are equally similar environmentally. Although MZ twins are genetically more similar than DZ twins, they are often environmentally more similar. This paper demonstrates that, even in the complete absence of any genetic factor and of any biases, the greater environmental similarity alone in MZ twins can result in higher concordance rate in MZ twins than in DZ twins. This is especially true when there are multiple environmental factors, which may have multiple exposure levels and/or interact strongly, although each of them may be of low risk. This may serve as a sobering antidote to the uncritical reliance on twin studies without examining the validity of the underlying assumptions.

Environment↗
PubMed2002

The Italian Twin Project: from the personal identification number to a national twin registry.

The unique opportunity given by the "fiscal code", an alphanumeric identification with demographic information on any single person residing in Italy, introduced in 1976 by the Ministry of Finance, allowed a database of all potential Italian twins to be created. This database contains up to now name, surname, date and place of birth and home address of about 1,300,000 "possible twins". Even though we estimated an excess of 40% of pseudo-twins, this still is the world's largest twin population ever collected. The database of possible twins is currently used in population-based studies on multiple sclerosis, Alzheimer's disease, celiac disease, and type 1 diabetes. A system is currently being developed for linking the database with data from mortality and cancer registries. In 2001, the Italian Government, through the Ministry of Health, financed a broad national research program on twin studies, including the establishment of a national twin registry. Among all the possible twins, a sample of 500,000 individuals are going to be contacted and we expect to enrol around 120,000 real twin pairs in a formal Twin Registry. According to available financial resources, a sub sample of the enrolled population will be asked to donate DNA. A biological bank from twins will be then implemented, guaranteeing information on future etiological questions regarding genetic and modifiable factors for physical impairment and disability, cancers, cardiovascular diseases and other age related chronic illnesses.

Aging↗
PubMed1997

Gender differences in twin-twin transfusion syndrome.

OBJECTIVE: To determine whether there is a gender discrepancy in severe twin-twin transfusion syndrome. METHODS: All cases of twin-twin transfusion syndrome evaluated between 1989 and 1996 were reviewed retrospectively. The following sonographic criteria were used: a single placenta, a thin membrane, the same gender, a combination of polyhydramnios-oligohydramnios, a stuck twin, and an estimated weight discordance exceeding 20%. At least five of six sonographic criteria were required for inclusion in the study. Only severe cases, which were defined as early onset (before 30 weeks' gestation), a combination of polyhydramnios and oligohydramnios, a stuck twin, fetal hydrops, fetal death, or the requirement of medical or invasive treatment, were included. Chorionicity was confirmed by placental examination when available. RESULTS: Thirty-seven twin pregnancies met the above criteria, of which 33 (89%) twin pairs were female. The median gestational age at presentation was 19 weeks (range, 15-29; standard deviation, 5.6). A single placenta, thin membrane, same gender, and polyhydramnios-oligohydramnios were present in every case. A stuck twin was noted in 34 of 37 cases (92%), and a growth discordance exceeding 20% was present in 26 of 36 (72%). Placental pathology, which was available in 31 (84%) cases, confirmed a monochorionic placentation in 29. Twenty-five (68%) cases had reduction amniocentesis, two were treated with indomethacin, one underwent a cord ligation, and in four cases, fetal death occurred before treatment was instituted. CONCLUSION: There is a significant female preponderance in pregnancies complicated by severe twin-twin transfusion syndrome. The reasons for this are nuclear, but they may be related to either placental or fetal gender-specific differences affecting a subset of monochorionic twin pregnancies.

Female↗
PubMed1995

Preliminary experience with endoscopic laser surgery for severe twin-twin transfusion syndrome.

BACKGROUND: In monozygotic twin pregnancies, there are placental vascular communications between the two fetuses. In 15 percent of such pregnancies there is an imbalance in net blood flow between the twins, resulting in the twin-twin transfusion syndrome. The recipient twin may have severe hydramnios during the second trimester of pregnancy, and there is a high risk of perinatal death and cerebral palsy in survivors. This condition can now be treated by endoscopic coagulation of the vascular anastomoses responsible for fetofetal transfusion with a neodymium:yttrium-aluminum-garnet (Nd: YAG) laser. METHODS: We performed intrauterine surgery in 45 pregnant women carrying twins at 15 to 28 weeks of gestation (median, 21); in each case there was severe hydramnios in one fetus due to the twin-twin transfusion syndrome. With the use of local anesthesia and continuous ultrasound visualization, a rigid fetoscope 2 mm in diameter, housed in a 2.7-mm cannula, was introduced transabdominally into the amniotic cavity of the recipient twin. A systematic search was made for all vessels approaching or crossing the membrane between the twins, and these were coagulated with an Nd:YAG laser by means of a fiber in the side arm of the cannula. RESULTS: Coagulation of the communicating vessels was successful in all cases. The total number of fetuses who survived to delivery was 48 (53 percent), and the number of pregnancies with at least 1 survivor was 32 (71 percent). Among the live-born infants, the median gestational age at delivery was 35 weeks (range, 25 to 40), and the median birth weight was 2098 g (range, 550 to 4252). The median interval between the endoscopic laser procedure and delivery was 14 weeks (range, 0 to 21). All the survivors were developing normally at a median age of 12 months (range, 2 to 24). CONCLUSIONS: Our preliminary experience suggests that the twin-twin transfusion syndrome can be treated effectively by endoscopic laser coagulation of the communicating placental vessels.

Endoscopy↗
PubMedDate not supplied

Diagnosis, pathophysiology, and treatment of chronic twin-to-twin transfusion syndrome.

The discovery of a 'stuck twin' during an ultrasound examination has often been equated with twin-to-twin transfusion based to a great extent on postnatal confirmation of discordant fetal size and hemoglobin concentration. However, the diagnosis of twin-to-twin transfusion cannot be made with certainty after birth since virtually all monochorionic gestations have placental anastomoses and there are many causes of growth deficiency and abnormal hemoglobin concentration. The purpose of this study is to investigate the pathophysiology of chronic twin-to-twin transfusion syndrome and apply the findings to the development of a management algorithm. In 42 twin gestations with stuck twin associated with acute hydramnios, we performed targeted ultrasound cordocentesis in each fetus and therapeutic amniocentesis. The diagnosis of chronic twin-to-twin transfusion syndrome required: sonographic evidence of monochorionicity; rapid reaccumulation of fluid after amniocentesis; discordant fetal size, and divergent fetal hematocrit measurements with at least one above or below the 95% confidence interval for gestational age. These criteria were met in 20 of 42 (48%) pregnancies. The mean gestation was 23.8 +/- 2 weeks (range 21-27 weeks). In 4 pregnancies, the transfer of adult RBCs from the donor to the recipient was documented. Monochorionicity was confirmed in all postnatally. All recipients had polycythemia and hyperproteinemia. Hydrops developed only in the recipient twin (6 of 20) and was associated with an elevated umbilical venous pressure. All pregnancies were treated with aggressive serial therapeutic amniocenteses. There was no objective evidence that amniocentesis altered the magnitude of the shunt.(ABSTRACT TRUNCATED AT 250 WORDS)

Amniocentesis↗
PubMed2001

Natural versus induced twinning and pregnancy outcome: a Dutch nationwide survey of primiparous dizygotic twin deliveries.

OBJECTIVE: To compare obstetrical outcome of twin pregnancies after assisted reproduction with that of natural twin pregnancies. DESIGN: Retrospective national database study. SETTING: Academic Medical Centre. PATIENT(S): One thousand ninety-three primiparous mothers registered in the Dutch National Birth Registry who gave birth to a dizygotic (DZ) twin (male/female) in 1994, 1995, and 1996. We compared 613 natural twin pregnancies and 480 twin pregnancies born after assisted reproduction. MAIN OUTCOME MEASURE(S): Gestational length, mode of delivery, mode of presentation of the children, birth weight, APGAR score, congenital anomalies, perinatal mortality rate, highest recorded maternal diastolic blood pressure, and maternal postpartum complications. RESULT(S): Rates of perinatal mortality and very premature parturition (<29 weeks) were lower in natural twin mothers. Overall, induced DZ twins were born 3.5 days earlier with a lower birth weight and APGAR score compared with controls. Rates of congenital anomalies and incidence of cesarean section were not different. The highest recorded diastolic blood pressure was lower in induced twinning with a 30% lower incidence of diastolic blood pressure >90 mm Hg. CONCLUSION(S): Obstetric outcome for induced DZ twin pregnancy is less optimal than in natural DZ twin pregnancy. Twinning in assisted reproduction is known for its contribution to the high rate of premature deliveries, but in addition being a subfertile patient undergoing treatment makes an intrinsic contribution to adverse events as well.

Adult↗