Parturition

• Parturition, or childbirth, is the process by which the fetus and placenta are expelled from the uterus at the end of pregnancy.
• It involves a series of complex physiological events and is typically divided into three stages: the first stage (latent and active phases of labour), the second stage (delivery of the baby), and the third stage (delivery of the placenta).

Mechanism of Parturition

1. Hormonal Factors:

   • The onset of labor is believed to be triggered by an interplay of hormones, including increased levels of estrogen, prostaglandins, and oxytocin.
   • These hormones stimulate uterine contractions, soften the cervix (the lower part of the uterus opening into the vagina), and promote the release of more oxytocin, creating a positive feedback loop that intensifies contractions.

2. Mechanical Factors:

   • The growing fetus and its movement within the uterine cavity exert mechanical pressure on the cervix and uterine wall.
   • This pressure is thought to contribute to the initiation of labor.

Stages of Parturition

First Stage of Labor: Cervical Dilation and Effacement

• This stage involves the gradual opening (dilation) and thinning (effacement) of the cervix in preparation for the baby’s birth.

1. Latent Phase:

   • This initial phase is characterized by the softening, shortening (effacement), and opening (dilation) of the cervix, aided by irregular and mild to moderate uterine contractions.
   • For first-time mothers, this phase can last from several hours to a few days.

2. Active Phase:

   • After the latent phase, the active phase begins with regular, stronger contractions and faster cervical dilation, progressing from 4 cm to 10 cm.
   • This phase involves increased pain and pressure, and typically lasts several hours.

Second Stage of Labor: Delivery of the Baby

• Once the cervix is fully dilated, this stage begins and involves the actual birth of the baby.

1. Pushing:

   • With the cervix fully dilated to 10 cm, the mother is encouraged to push with each contraction to help the baby descend through the birth canal.
   • The emergence of the baby’s head, known as crowning, signals that birth is near.

2. Delivery:

   • The final pushes lead to the birth of the baby.
   • The healthcare provider assists by guiding the baby out, and the umbilical cord is clamped and cut safely.

Third Stage of Labor: Delivery of the Placenta

• This stage involves the delivery of the placenta, which follows the birth of the baby.

1. Separation and Expulsion:

   • After the baby is born, uterine contractions continue, leading to the separation of the placenta from the uterine wall.
   • The mother may be asked to push gently to aid in the expulsion of the placenta, which typically occurs within 5 to 30 minutes post-delivery.

2. Examination:

   • The healthcare provider examines the delivered placenta to ensure it is complete, with no fragments left behind in the uterus.
   • Retained placenta fragments could lead to postpartum complications, so careful examination is crucial.

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