Improved estimates of discordance ratios in twin studies

In the study of monozygotic twins relative to disease and risk factors, particular interest focuses on the subset who are discordant for some suspected risk factor (for example, smoking), since such twins constitute a natural case-control pair. In such studies, questionnaires designed to identify the status of all twin pairs are sometimes error prone and can yield misleading estimates of the concordance-discordance ratios. Greater efforts to verify the characteristics of apparently discordant pairs than to verify those of apparently concordant pairs can result in the 'unequal ascertainment' fallacy. Using the results of a questionnaire with known error rates and the 'apparent' frequencies yielded, we present unbiased, maximum likelihood estimates of the 'true' proportions of concordant and discordant pairs. concordant and discordant pairs. We also present approximate covariances among these estimates.     

Comorbidity and social phobia: evidence from clinical,epidemiologic, and genetic studies

This paper reviews evidence from clinical, epidemiologic, and family studies regarding the association between social phobia and other syndromes. Social phobia is strongly associated with other anxiety disorders, substance abuse, and affective disorders in both clinical and community samples. An average of 80% of social phobics identified in community samples meet diagnostic criteria for another lifetime condition. Social phobia is most strongly associated with other subtypes of anxiety disorders, with an average of 50% of social phobics in the community reporting a concomitant anxiety disorder including another phobic disorder, generalized anciety, or panic disorder. Approximately 20% of subjects in the community meet lifetime criteria for a major depressive disorder. The onset of social phobia generally precedes that of all other disorders, with the exception of simple phobia. Both clinical severity and treated prevalence are consistently greater among social phobics with comorbid disorders The results of family and twin studies reveal that shared etiologic factors explain a substantial proportion of the comorbidity between social phobia and depression, whereas the association between social phobia and alcoholism derives from a nonfamilial causal relationship between the two conditions. Clinical and phenomenologic implications of these findings are discussed.     

The Dutch twin register: Growth data on weight and height

As part of a longitudinal developmental study of newborn and young Dutch twins, data on weight and height are collected. Birth weight and height are available for 3275 pairs; data on growth, for 1390 pairs.     

双胎妊娠44例临床分析

本文对我院1990～1995年间44例双胎妊娠的分娩方式进行了分析。指出双胎妊娠由于胎位异常、产力异常及妊娠并发症多等因素,难产及手术产率均较单胎明显增高。在25例经阴道分娩的双胎中,阴道手术产率为64％,本组双胎剖宫产率为43.22％。本文认为双胎妊娠的分娩方式应掌握以下原则:当第一胎儿为臀泣、第二胎位为头位,尤其是胎儿较大、羊水较少时,应考虑剖宫产。而单纯的第二胎儿臀位可以经阴道分娩,不必常规剖宫产。     

双胎妊娠围生儿预后相关因素分析

目的　探讨双胎妊娠新生儿窒息、围生儿死亡的相关因素。方法　回顾分析 2 5 5例双胎妊娠新生儿Apgar评分、新生儿窒息、围生儿死亡与孕周、新生儿体重、分娩方式的关系。结果　双胎妊娠孕 37～ 39+ 6w组Apgar评分最高、新生儿窒息率最低 ,≥ 2 5 0 0g组Apgar评分最高 ,新生儿窒息率、围生儿死亡率最低。孕周、新生儿体重 4组比较差异均有非常显著性(P <0 0 1)。剖宫产组比阴道分娩组Apgar评分高 ,新生儿窒息率、围生儿死亡率均低 ,2组比较Apgar评分、围生儿死亡率差异无显著性 (P >0 0 5 )。 2组比较新生儿窒息率差异有非常显著性 (P <0 0 1)。结论　双胎妊娠估计每个胎儿体重≥ 2 5 0 0g时 ,宜选择 37～ 39+ 6w终止妊娠为宜。加强孕期、围生期保健 ,积极防治各种并发症 ,适当放宽剖宫产指征 ,避免早产 ,减少低体重儿出生 ,是降低双胎围生儿死亡率、改善其预后的重要措施。     

双生子骨龄遗传度的性别差异分析

[目的 ]探讨双生子骨龄遗传度的性别差异。 [方法 ] 2 0 0 2～ 2 0 0 3年在青岛市进行双生子募集工作 ,经知情同意 ,调查 190对双生子。应用微卫星DNA基因扫描和分型技术 ,进行卵型鉴定 ,通过拍摄手腕骨X片 ,按照《中国人手腕骨发育标准CHN法》评价骨龄 ,采用经典的Holzinger公式估算遗传度。[结果 ]骨龄遗传度男性双生子为 0 813 ,女性双生子为 0 682 ;幼年期男性双生子 0 83 6,明显高于同期女性双生子 ( 0 3 2 2 ) ;童年期男、女性双生子分别为 0 65 8、0 760 ;青春期达到最高 ,男、女性双生子分别为 0 941、0 817。 [结论 ]遗传因素对男性骨发育的影响高于女性。遗传因素对男、女性骨发育的影响随年龄的增长而逐步体现 ,青春期达到最高 ,青春期神经内分泌变化在该过程发挥重要作用。     

Fetal circulation and placental blood flow in monochorionic twins

Objectives. Twin to twin transfusion syndrome (TTTS) is one of the most important problems for perinatal management of monochorionic twins. Since TTTS is deeply related to the prognoses of both fetuses, fetal circulation and placental blood flow of monochorionic twins were studied with the purpose of clarifying characteristic features.

Methods. The patterns and numbers of vascular anastomoses were checked on the placental surface, arterio-arterial (A-A) anastomosed vessels by ultrasound, and circulatory changes were studied with relation to uterine contraction.

Results. The high risk of monochorionic twin pregnancies was largely related to the patterns of vascular anatomy of the placenta and numbers of anastomosed vessels. The first placental vascular connection detected in vivo was the A-A anastomosis characterized by the bidirectional flow waveform in pulsed Doppler velocimetry.

Conclusion. TTTS is related to anastomosed vessels on the surface of placenta. To manage and prevent TTTS, fetal circulation and placental blood flow should be carefully observed.