孪生的机制。五、联体双胎、干细胞与钙模型。
Mechanisms of twinning. V. Conjoined twins, stem cells and the calcium model.
作者信息
Steinman Gary
机构信息
Department of Obstetrics and Gynecology, Long Island Jewish Medical Center, New Hyde Park, New York, USA.
出版信息
J Reprod Med. 2002 Apr;47(4):313-21.
OBJECTIVE
To examine the possible role of calcium in conjoined twinning.
STUDY DESIGN
Conjoined (CJ) twins are an extreme example of monozygotic (MZ) twinning. Data were collected from various sources on factors to which gravidas who deliver CJ twins were exposed around the time of conception.
RESULTS
A significant number of such women were subjected to environmental triggers. Of particular interest is increased CJ twinning following use of oral contraceptives. It is hypothesized that this resulted from prolonged ovulatory dysfunction in lightweight women. The incidence of uniovular twinning is inversely related to women's prepregnancy weights.
CONCLUSION
These observations are consistent with the proposed general model of MZ twinning. Factors that induce calcium depression and delayed implantation encourage uniovular duplication in general and CJ twinning in particular.
目的
研究钙在联体双胎形成中可能发挥的作用。
研究设计
联体双胎是单卵双胎的极端例子。从多个来源收集了关于分娩联体双胎的孕妇在受孕前后接触的各种因素的数据。
结果
大量此类女性受到环境触发因素影响。特别值得关注的是口服避孕药使用后联体双胎发生率增加。据推测，这是由于体重较轻的女性排卵功能长期失调所致。单卵双胎的发生率与女性孕前体重呈负相关。
结论
这些观察结果与所提出的单卵双胎形成的一般模型一致。诱导钙水平降低和着床延迟的因素通常会促使单卵双胎发生，尤其是联体双胎。
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