Normal labour:
Definition of labour:
Labor is defined as the onset of a sequence of painful regular uterine contractions that results in progressive effacement and dilatation of the cervix with descent of the presenting part and voluntary bearing-down efforts leading to the expulsion of the products of conception through the vagina.
There are some terms and definitions at the end of (chapter 9 labour) read them in (obstetrics by ten teachers): attitude, caput saccedaneum, effacement of the cervix, engagement, position, presenting part, partogram, show, station, term, vertex, synclitism.
Physiologic Preparation for Labor:
Prior to the onset of true labor, several preparatory physiologic changes commonly occur. lightening, usually occurs 2 or more weeks before labor in first pregnancies. In women who have had a previous delivery, lightening often does not occur until early labor.
Clinically, the mother may notice a flattening of the upper abdomen and increased pressure in the pelvis. This descent of the fetus is often accompanied by a decrease in discomfort associated with crowding of the abdominal organs under the diaphragm (eg, heartburn, shortness of breath), and an increase in pelvic discomfort and frequency of urination.
During the course of several days to several weeks before the onset of true labor, the cervix begins to soften, efface, and dilate.
In many cases, when labor starts, the cervix is already dilated 1–3 cm in diameter. This is usually more pronounced in the multiparous patient, the cervix being relatively more firm and closed in nulliparous women.
With cervical effacement, the mucus plug within the cervical canal may be released. When this occurs, the onset of labor is sometimes marked by the passage of a small amount of blood-tinged mucus from the vagina known as bloody show.
Stages of labour
Normal labor is a continuous process that has been divided into three stages for purposes of study, with the first stage further subdivided into two phases, the latent phase and the active phase. The first stage of labor is the interval between the onset of labor and full cervical dilatation.
The duration of the first stage of labor in primipara patients is noted to range from 6–18 hours, while in multiparous patients the range is reported to be 2–10 hours. The lower limit of normal for the rate of cervical dilatation during the active phase is 1.2 cm per hour in first pregnancies and 1.5 cm per hour in subsequent pregnancies.