Explain the Steps of Parturition


The duration of pregnancy in human beings is about 9 months ± 7 days which is also called the gestation period. At the end of the pregnancy vigorous contraction of the uterus causes delivery or expulsion of the fetus. The act of expelling the full-term young one from the mother’s uterus at the end of the gestation period is called Parturition.

Steps of Parturition:

1. Stage of Dilation:

Early in dilation, uterine contractions or labor pains occur at intervals of 20-30 minutes and last about 40 seconds. They are then accompanied by slight pain. The time from the onset of labor pain to the complete dilation of the cervix is called the stage of dilation. This stage lasts 6-12 hours. During this stage, regular contraction of the uterus usually rupture the amniotic sac and complete dilation of the cervix occur. The fluid flow out through the vagina.

2. Stage of Expulsion:

The time from complete cervical dilation to delivery of the fetus is the stage of expulsion. It lasts 10 minutes to several hours. The baby passes through the cervix and vagina & is born. About the time that the cervix becomes fully dilated, the amnion breaks, and the force of the involuntary uterine contractions may be augmented by voluntary bearing-down efforts of the mother.

With each labor pain, she can take a deep breath and then contract her abdominal muscles. The increased intra-abdominal pressure thus produced may equal or exceed the force of the uterine contractions. These bearing-down efforts may double the effectiveness of uterine contractions. As the child descends into and passes through the birth canal, the sensation of pain is often increased. This condition is especially true in the terminal phase of the stage of expulsion when the child’s head distends and dilates the maternal tissues as it is being born.

3. Placental Stage:

The time after delivery until the placenta is expelled by powerful uterine contraction is the placental stage. In about 28-35 days, the uterus returns fully to its non-pregnant state. With the expulsion of the child, the cavity of the uterus is greatly diminished. As a consequence, the site of placental attachment becomes markedly reduced in size, with the result that the placenta is separated in many places from the membrane lining the uterus.

Within a few minutes, subsequent uterine contractions complete the separation and force the placenta into the vagina which is expelled by a bearing down effort. The third stage is labor, accordingly is of short duration, Seldon lasting longer than 15 minutes. Occasionally, however, the separation may be delayed and accompanied by bleeding in which case surgical removal of the placenta is necessary.