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Taller women are more likely to have twins, according to a US study. Gary Steinman, an obstetrician at New York's Long Island Jewish Medical Center, compared the heights of 129 women who gave birth to twins or triplets with the average height of women in the United States and found women with multiple-birth pregnancies averaged more than an inch taller. Steinman, whose study is being published in the September issue of the Journal of Reproductive Medicine, said the reason seems to be an insulin-like growth factor, which has been positively linked to both height and twinning. Insulin-like growth factor is a protein that is released from the liver in response to growth hormone. It increases the sensitivity of the ovaries to follicle stimulating hormone, thereby increasing ovulation, the study said. "Any circumstance that affects the amount of available insulin-like growth factor so as to modify the sensitivity of the ovary to follicle-stimulating hormone appears to govern the rate of spontaneous twinning," Steinman said in a statement. Previous studies have demonstrated that shorter people have significantly lower levels of this protein and that countries with taller women have higher rates of twinning compared to countries with shorter women. In a previous study, Steinman found that women who consume animal products, specifically dairy, were five times more likely to have twins. Cows, like humans, produce insulin-like growth factor in response to growth hormones and release it into the blood, and the protein makes its way into their milk. (Agencies)

美國一項研究表明，個子高的女性生雙胞胎的可能性較大。 紐約長島猶太醫療中心的婦產科醫師加里·斯汀曼將129名生過雙胞胎或三胞胎的女性的身高與美國女性的平均身高進行了對比，結果發現生過多胞胎的女性平均身高要高出2.54厘米。 斯汀曼的此項研究結果在《生殖醫學》的第九期上發表，他說，這可能和類胰島素生長因子有關，類胰島素生長因子與身高和孿生幾率呈正相關關系。 類胰島素生長因子是人體肝臟在生長激素的作用下分泌出的一種蛋白質。研究表明，類胰島素生長因子能增強卵巢對促卵泡激素的敏感度，從而促進排卵。 斯汀曼在一份聲明中提到："任何能影響類胰島素生長因子分泌量的因素都會改變卵巢對促卵泡激素的敏感度，從而影響自然孿生的幾率。" 之前已有研究表明，個矮的人體內分泌的類胰島素生長因子量要低很多，此外，女性個子較高的國家比女性個子較矮的國家的雙胞胎出生率高。 斯汀曼在此前的一個研究中發現，常食用畜產品尤其是奶制品的女性生雙胞胎的幾率比不食用這些食品的女性大五倍。奶牛和人一樣，也能在生長激素的作用下分泌類胰島素生長因子，這種蛋白質被釋放到血液里，從而進入到牛奶中。 (英語點津姍姍編輯)