[文献资料]参考文献

1 ﹒ Tsikouras P，Galazios G，Zalvanos A，et al ． Transvaginal sonographic assessment of the cervix and pre ter mlabor ． Clin Exp Obstet Gynecol，2007，34.5 ﹒ Facco FL，Nash K，Grobman WA ． Are women who have had a preter mt win delivery at greater risk of preter ......