MedTerms Medical Dictionary

Labor: Childbirth, the aptly-named experience of delivering the baby and placenta from the uterus to the vagina to the outside world. There are two stages of labor. During the first stage (called the stage of dilatation), the cervix dilates fully to a diameter of about 10 cm. In the second stage (called the stage of expulsion), the baby moves out through the cervix and vagina to be born.

The first stage of labor, the time when the cervix dilates, is conventionally divided into two phases:

• The latent phase -- Contractions become progressively more coordinated and the cervix dilates to 4 cm. The latent phase averages about 8 hours in a nullipara (a woman having her first baby) and 5 hours in a multipara (a woman with multiple pregnancies). This phase is considered distinctly abnormal if it lasts more than 20 hours in a nullipara or more than 12 hours in a multigravida.

• The active phase -- The cervix becomes fully dilated and the presenting part of the baby descends into the midpelvis. The active phase averages about 5 hours in nulliparas and 2 hours in multiparas.

The second stage of labor, the time from full cervical dilation to the delivery of the baby, lasts on the average 2 hours in nulliparas and l hour in multiparas. It may last an additional hour if there is an epidural In a spontaneous delivery, the woman must supplement her uterine contractions by bearing down.

In Latin, the word labor means "a troublesome effort or suffering." Parturition is another term for "labor." It comes from the Latin parturire, "to be ready to bear young" and is related to partus, "to produce." To labor in this sense is to produce.

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