Onset of Labour

Subject: Midwifery II (Theory)

Overview

The uterus has oxytocin receptors. With the start of labor, oxytocin receptors are enhanced in the uterus. Depending on changes in fetal pituitary-adrenal activity, it is possible that some signal is provided by the feto-placental unit, which is important for the metabolism of estrogen. The fetal adrenal cortex produces precursors for the synthesis of estrogen, which is rapidly produced by the placenta during the last week of pregnancy. A decrease in progesterone production may increase estrogen's ability to induce uterine muscle growth and prostaglandin (PG) synthesis. Prostaglandins are crucial for starting and maintaining labor. Sign and symptoms of onset of labour are feeling of activity and lightness on the part of the patient, diminution of the abdominal protuberance, increased vaginal secretion, lightening,Braxton hicks contraction,show, rupture of the membrane and ripening of cervix.

Onset of Labour

  • Oxytocin
    • The uterus has oxytocin receptors. With the start of labor, oxytocin receptors are enhanced in the uterus. Then, oxytocin encourages the decidua to release prostaglandins. Both the decidua and the placenta produce more oxytocin. At the time of birth, the level of oxytocin peaks.
  • Feto-placental contribution
    • Depending on changes in fetal pituitary-adrenal activity, it is possible that some signal is provided by the feto-placental unit, which is important for the metabolism of estrogen. The fetal adrenal cortex produces precursors for the synthesis of estrogen, which is rapidly produced by the placenta during the last week of pregnancy.
  • Progesterone 
    • A decrease in progesterone production may increase estrogen's ability to stimulate uterine muscle growth and prostaglandin (PG) synthesis.
  • Estrogen 
    • The probable mechanisms are-
      • - Increases the release of oxytocin from the maternal pituitary.
      • - Promotes the synthesis of receptors for oxytocin in the myometrium and decidua.
  • Prostaglandins
    • Prostaglandins are the important factors which initiate and maintain labour.
    • Prostaglandins stimulate smooth muscle to contract. The major sites of synthesis
    • of prostaglandins are amnion, chorion, decidua cells, and myometrium.
  • Neurological factor
    • Labour may also be initiated through nerve pathways. Both α and β adrenergic receptors are present in the myometrium, estrogen causing the α receptors and progesterone the β receptors to function predominately. The contractile response is initiated through the α receptors of the post -ganglionic nerve fibers and around the cervix and the lower part of the uterus. The pressure of presenting part on the nerve- endings in the cervix may play some part.
  • Mechanical factors
    • Stretching effect on the myometrium by the growing size of the fetus and liquor amnii can explain the onset of labour at least in twins and polyhydramnios. However, "optimal distension theory" fails to account for otherwise cause preterm labour.

Sign and symptoms of onset of labour

  • The patient reports feeling active and lighthearted.
  • The abdominal protuberance decreasing
  • Mre vaginal secretions
  • A sympathetic irritation that affects the bladder and, occasionally, the rectum.
  • The mother would feel the fetus' fall and see a change in the shape of her abdomen.
  • Painless irregular contractions are known as Braxton Hicks contractions.
  • Horrific show
  • Energy spike: caused by a shift in estrogen and progesterone levels
  • Back pain and sacroiliac pressure are both worse
  • Cervical ripening: a sense of cervix that is as soft as butter
  • Membrane rupture: "bag of water."
Things to remember
  • There is oxytocin receptor in the uterus. Oxytocin receptors are increased in the uterus with the onset of labour.
  • It is possible that some signal is given from the feto-placental unit which plays a major role in estrogen metabolism depending on changes in fetal pituitary- adrenal activity the fetal adrenal cortex produces precursors for the synthesis of estrogen which rises rapidly during the last week from the placenta.
  • A decrease in progesterone production may stimulate prostaglandins (PG) synthesis and enhance the effect of estrogen which has a stimulating effect on uterine muscle.Prostaglandins are the important factors which initiate and maintain labour.
  • Sign and symptoms of onset of labour are feeling of activity and lightness on the part of the patient, diminution of the abdominal protuberance, increased vaginal secretion, lightening,Braxton hicks contraction,show, rupture of the membrane and ripening of cervix.
Questions and Answers

 

Sign and symptoms of onset of labour

  • The patient reports feeling active and lighthearted.
  • The abdominal protuberance decreasing.
  • More vaginal secretions.
  • A sympathetic irritation that affects the bladder and, occasionally, the rectum.
  • The mother would feel the fetus' fall and see a change in the shape of her abdomen.
  • Painless irregular contractions are known as Braxton Hicks contractions.
  • Horrific show.
  • Energy spike: caused by a shift in estrogen and progesterone levels.
  • Back pain and sacroiliac pressure are both worse.
  • Cervical ripening: a sense of cervix that is as soft as butter.
  • Membrane rupture: "bag of water."

Onset of Labour

  • Oxytocin

The uterus has oxytocin receptors. With the start of labor, oxytocin receptors are enhanced in the uterus. Then, oxytocin encourages the decidua to release prostaglandins. Both the decidua and the placenta produce more oxytocin. At the time of birth, the level of oxytocin peaks.

  • Feto-placental Contribution

It is possible that some signal is given from the feto-placental unit which plays a major role in estrogen metabolism depending on changes in fetal pituitary- adrenal activity the fetal adrenal cortex produces precursors for the synthesis of estrogen which rises rapidly during the last week from the placenta.

  • Progesterone

A decrease in progesterone production may stimulate prostaglandins (PG) synthesis and enhance the effect of estrogen which has a stimulating effect on uterine muscle.

  • Estrogen 

The probable mechanisms are

  • Increases the release of oxytocin from the maternal pituitary.
  • Promotes the synthesis of receptors for oxytocin in the myometrium and decidua.

 

  • Prostaglandins

Prostaglandins are the important factors which initiate and maintain labour.

Prostaglandins stimulate smooth muscle to contract. The major sites of synthesis

of prostaglandins are amnion, chorion, decidua cells, and myometrium.

  • Neurological Factor

Labour may also be initiated through nerve pathways. Both α and β adrenergic receptors are present in the myometrium, estrogen causing the α receptors and progesterone the β receptors to function predominately. The contractile response is initiated through the α receptors of the post -ganglionic nerve fibers and around the cervix and the lower part of the uterus. The pressure of presenting part on the nerve- endings in the cervix may play some part.

  • Mechanical Factors

Stretching effect on the myometrium by the growing size of the fetus and liquor amnii can explain the onset of labour at least in twins and polyhydramnios. However, "optimal distension theory" fails to account for otherwise cause preterm labour.

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