Читайте англоязычную литературу, там все хорошо написано. С 6 недель нерегулярные сокращения матки начинаются.Braxton Hicks contractions are sporadic uterine contractions that start about 6 weeks into your pregnancy, although you won't be able to feel them that early. You probably won't start to notice them until sometime after mid-pregnancy, if you notice them at all.  http://www.babycenter.com/0_braxton-hicks-contractions_156.bcТут еще это обсуждали http://eva.ru/topic/53/2347707.htm?messageId=58312633