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The process of expulsion of the fetus and the placenta from the uterus. The stages of l. include: first stage, beginning with the onset of uterine contractions through the period of dilation of the os uteri; second stage, the period of expulsive effort, beginning with complete dilation of the cervix and ending with expulsion of the infant; third s. or placental stage, the period beginning at the expulsion of the infant and ending with the completed expulsion of the placenta and membranes. [L. toil, suffering]
- missed l. brief uterine contractions which do not lead to l. and expulsion of the infant, but which cease, resulting in the indefinite retention of the fetus (usually lifeless) either in utero or in the abdominal cavity.
- premature l. onset of l. after 20 weeks and before the 37th completed week of pregnancy dated from the last normal menstrual period.
- trial of l. after cesarean section the attempt to deliver vaginally after a cesarean section; carries some risk of rupture of the uterine scar.
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la·bor or Brit la·bour 'lā-bər n the physical activities involved in parturition consisting essentially of a prolonged series of involuntary contractions of the uterine musculature together with both reflex and voluntary contractions of the abdominal wall <drugs that induce \labor> <went into \labor after a fall> also the period of time during which such labor takes place
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la·bor (laґbər) [L. “workâ€] the function of the female organism by which the product of conception is expelled from the uterus through the vagina to the outside world. Labor may be divided into four stages: The first (the stage of cervical dilatation) begins with the onset of regular uterine contractions and ends when the os is completely dilated. The second stage (stage of expulsion) extends from the end of the first stage until the expulsion of the infant is completed. The third stage (placental stage) extends from the expulsion of the child until the placenta and membranes are expelled. The fourth stage denotes the hour or two after delivery, when uterine tone is established. See also labor pains, under pain.Medical dictionary. 2011.