The onset of parturition, or child birth, involves a series of physiological changes. it typically begins with uterine contractions, triggered by hormonal shifts such as increased levels of oxytocin. As contractions intensify, the cervix gradually dilates to allow passage for the baby. Rupture of the amniotic sac may occur, signaling the progression of labor. Throughout this process, maternal instincts and the release of various hormones it's a complex and orchestrated events crucial for the safe delivery of the infant, this process marks the culmination of pregnancy and the beginning of the postpartum period.
prostaglandin softens the cervix followed by increased uterine contraction.
the onset of parturition typically involved the following stages.
1] Initiation ( onset of labor)
2] cervical change
3] Engagement and descent
4] Rupture of membranes
5] Active labor
6] Delivery of baby
7] delivery of placenta
this process is dynamic and can vary among individuals. it's important to recognize signs of labor, such as regular contractions and changes in cervical dilation, for appropriate medical attention
3. • Parturition means giving birth
• Labor is the process of expelling the Fetus
• Strong contraction of Uterus
Uterus Becomes More
Excitable
Increase in strength of
rhythmic contraction
Hormonal Factors Mechanical Changes
• Incease in Estrogen
progesteron ratio
• Realease of Oxytocin
• Fetal Hormones
• Onset of Labor
• Mechanics of Parturiton
(E/P
)
4. Increase in Estrogen progesteron Ratio
• Progesterone – decrease excitability and contractility
• Estrogen – increase excitability and contractility
• During the early 30 weeks of pregnancy estrogen to progesterone ratio is balanced
• After about 30th week
- estrogen continue to increase
- progesterone reaches a stationary level
- E/P is increased
- contractility progressively increases
- labor begins when progesterone’s inhibition is overcome by an increase in
the level of estrogen
5. Release of Oxytocin
- oxytocin has been proved to be involved in increased contraction of
the uterus
* oxytocin receptor in uterine muscles increase in the later part of
the Pregnancy
* Rate of oxytocin secretion has been seen to be high at the time of
delivery
* Absence of posterior pituitary – prolonged labor
* Experimental irritation or stretching of the cervix increases the
production of oxytocin
6.
7. Fetal Hormone
- Fetal posterior pituitary produce large amount of oxytocin
- fetal adrenal cortical cortisol is also oxytocic
- Prostaglandins from the fetal membrane towards the end of
pregnancy help the contractility during labor
Fetal Pituitary Gland
Fetal Adrenal Gnland
Fetal Membrane
Oxytocin
Cortisol
Prostaglandins
Increase in Uterine Contraction
8. Onset of labor
• This is the forceful muscular contraction of the uterus that happens at the time of birth. As this
process require some sort of energy along with the work that’s why this process is given the name
Labor .
• When the mother reaches the end of the gestation period the baby turns its position in which the
head portion remains in downward and the leg portion remains upwards.
• The labor starts after the completion of the gestation period which causes labor pain.
Most of Pregnancy
Weak and Slow Rhythmic
Contraction of Uterus
Braston-Hicks
Contraction
End of Pregnancy Hours Before Parturition
Becomes Strong Contraction Exceptionally Strong Contractio
• Increase Straching of Cervix
• Forces Baby thrigh Birth Canal
Parturition
9. Baby’s Head
Streaches Cervix
Uterine
Contraction
Baby is Pushed
Forward
Post Pituitory Oxytocin
Weak and Slow
Rhythemic Contractions
Strong Contractions
Due to Positive Feedback
Finally Expelled
+
+
+
If there is a continous
Strong contraction
Uterine Spasm
Stop Blood Flow through
Placenta
10. Stages of Parturition
• There are three Stages of Parturition
• Dilation
• Expulsion
• Placental Birth
First Stage of Labor
Second Stage of Labor
Onset of Labor
Full Dilation of Cervix
Expulsion of Fetus
11. Dilation
• Period that lasts long about 12 hr.
• Regular peristaltic contraction occurs
• That causes movement of the foetus downward
• And amnion and chorion membranes break out and fluid lubricates the vagina
• This stage is divided into a latent phase, an active phase and a transition phase.
12. Expulsion
• It lasts long about 20 min. to one hour
• In this period the abdominal wall along with the uterus contract continuously which dilates the
vagina and cervix and due to this contraction, the baby is expelled out to the outside world where
he draws his first breath
13. Fig:1 Hydrostatic action of Membranes in effecting cervical effacement and dilatation. with labor
progression, note the changing relation of the internal and external os (A) (B) (C)
14. Placental birth
• It’s after birth period which occurs for just 10-45 min. in which the uterus begins to shrink.
• The placenta becomes free from the implantation site.
• The placenta umbilical cord, and fetal membranes are expelled by another series of contractions of
the uterus.
Uterus Continues to Contract
Shearing effect between
walls of Uterus and Placenta
Placenta seperate from
implantation site
opening of Placental Sinus Bleeding (350 ml) Fig:2 Diminution in size of placental site after after birth of
the infant A. Spatial relations before birth. B. Placental
spatial relation after birth
15. Labor pains
• Labor Pain isone of the most intense pain that Women can experience
• Human body can bear up to 45 dal of pain
• During Labor mother feels up to 57dal of pain
• this is similar to 20 bones fractures at the same time
• This pain is situated at 32 and 36 points respectively for prepared child birth and unprepared child
birth in the Mc Gill Pain Scale
16. • “Medical Physiology” Elsevier (2016)
• “Physiology” Elsevier (2017)
• “Human Anatomy and Physiology” Pearson (2018)
• “Principle of Anatomy and Physiology” Wiley (2014)
• “Reassessing the labor duration in nulliparous women” American Journal of Obstetrics and
Gynaecology (2015)
