Objective: To study the changes of the gap junctions (GJS) in the uterine smooth muscle cells at various stages of labor, and its relationship with the onset of labor.
Methods: 18 women (38 to 41 gestational weeks) were divided into three groups: not-in-labor, pre-labor, active in labor and six cases in each group. The uterine myometrium tissues were observed by transmission electron microscopy (TEM) and lanthanum tracing method.
Results: The lengths and areas of GJS in uterine corpus and lower segment in the active in labor group were significantly larger than that of the other 2 groups, but there was no significant difference between the not-in-labor and pre-labor groups. The area but not the lengths of GJS in corpus was significant larger than that in the lower segment in the active in labor group.
Conclusion: The great increase of length and areas of GJS in all parts of the uterine smooth muscle was closely correlated with onset of labor.