72 Physiology of Labor
- Stages of Childbrith. The process of childbirth can be divided into three stages: cervical dilation, expulsion of the newborn, and afterbirth.
- Adjustments of the Infant at Birth and Postnatal Stages. From a fetal perspective, the process of birth is a crisis. ...
- Lactation. ...
- Summary of Birth and Lactation. ...
What is the physiology of Labor onset?
Introduction. The physiological processes that regulate parturition and the onset of labor continue to be defined. It is clear, however, that labor onset represents the culmination of a series of biochemical changes in the uterus and cervix. These result from endocrine and paracrine signals emanating from both mother and fetus.
What is the mechanism of Labor?
The "mechanism of labor" refers to the sequencing of events related to posturing and positioning that allows the baby to find the "easiest way out."
What role does the fetus play in the process of Labor?
For the most part the fetus is a passive respondent in the process of labor, while the mother provides the uterine forces and structural configuration of the passageway through which the passenger must travel. For a normal mechanism of labor to occur, both the fetal and maternal factors must be harmonious.
What are the stages of Labour?
As the cervix dilates, the mucus plug formed during pregnancy is lost and women might notice a bloody mucoid discharge. The first stage of labour can further be divided into 3 phases: the latent phase, the active phase and the transitional phase.
What is the physiology of the first stage of labour?
The first stage begins when spaced uterine contractions of sufficient frequency, intensity, and duration are attained to bring about cervical thinning, or effacement. This labor stage ends when the cervix is fully dilated—about 10 cm—to allow passage of the term-sized fetus.
What are the 3 physiological stages of labor?
Labour has three stages:The first stage is when the neck of the womb (cervix) opens to 10cm dilated.The second stage is when the baby moves down through the vagina and is born.The third stage is when the placenta (afterbirth) is delivered.
What are the physiological changes in labour?
The major anatomo-physiological changes of the maternal cardiovascular system happen throughout gestation and include an increase of blood volume, cardiac output, maternal heart rate, decrease of arterial blood pressure, and systemic vascular resistance.
What is happening physiologically during labor and birth?
As labor nears, oxytocin begins to stimulate stronger, more painful uterine contractions, which—in a positive feedback loop—stimulate the secretion of prostaglandins from fetal membranes. Like oxytocin, prostaglandins also enhance uterine contractile strength.
What are the 7 mechanisms of labor?
Anglo-American literature lists 7 cardinal movements, namely engagement, descent, flexion, internal rotation, extension, external rotation, and expulsion.
What is the physiology of second stage of labour?
The second stage of labor refers to the period that elapses between the onset of full dilatation of the cervix, and delivery of the fetus. It is further divided into a “passive” phase which involves a progressive descent and rotation of the presenting part, and an ”active” phase of maternal expulsive efforts.
What is the physiology of the delivery process?
Term labor is a physiologic process involving a sequential, integrated set of changes within the myometrium, decidua, and cervix that occur gradually over a period of days to weeks, culminating in rapid changes over hours that end with expulsion of the products of conception (fetus and placenta).
What is physiology parturition?
Parturition is the process of giving birth. It results from a complex interplay of maternal and fetal factors due to the sequential maturation of an endocrine organ communication system.
What is physiological changes in pregnancy?
Some of the changes in maternal physiology during pregnancy include, for example, increased maternal fat and total body water, decreased plasma protein concentrations, especially albumin, increased maternal blood volume, cardiac output, and blood flow to the kidneys and uteroplacental unit, and decreased blood pressure ...
What physiologically triggers labor?
Typically associated with stress, a rise in epinephrine increases your levels of prostaglandin and cortisol, which stimulate contractions and help give you the energy to push during stage 2 of labour.
What are the 4 stages of labor?
Labor happens in four stages:First stage: Dilation of the cervix (mouth of the uterus)Second stage: Delivery of the baby.Third stage: Afterbirth where you push out the placenta.Fourth stage: Recovery.
What are the physiologic changes during postpartum?
In the immediate postpartum period, cardiac output increases maximally and can rise 80% above pre-labor values and approximately 150% above non- pregnant measurements. An increase in stroke volume as well as in heart rate maintains the increased cardiac output.
What are the physiologic changes during postpartum?
In the immediate postpartum period, cardiac output increases maximally and can rise 80% above pre-labor values and approximately 150% above non- pregnant measurements. An increase in stroke volume as well as in heart rate maintains the increased cardiac output.
What are the physiological changes during pregnancy PDF?
During pregnancy, some changes in maternal physiology can occur including increased maternal fat, blood volume, cardiac output, and blood flow to the kidneys and uteroplacental unit, decreased blood pressure, delayed gastrointestinal motility, and gastric emptying.
Stages of Childbrith
The process of childbirth can be divided into three stages: cervical dilation, expulsion of the newborn, and afterbirth.
Adjustments of the Infant at Birth and Postnatal Stages
From a fetal perspective, the process of birth is a crisis. In the womb, the fetus was snuggled in a soft, warm, dark, and quiet world. The placenta provided nutrition and oxygen continuously.
Lactation
Lactation is the process by which milk is synthesized and secreted from the mammary glands of the postpartum female breast in response to an infant sucking at the nipple.
Summary of Birth and Lactation
The first breath a newborn takes at birth inflates the lungs and dramatically alters the circulatory system, closing the three shunts that directed oxygenated blood away from the lungs and liver during fetal life. Clamping and cutting the umbilical cord collapses the three umbilical blood vessels.
What is the result of labor onset?
It is clear, however, that labor onset represents the culmination of a series of biochemical changes in the uterus and cervix. These result from endocrine and paracrine signals emanating from both mother and fetus.
What is the composite of the average dilatation curve for labor in nulliparous women?
The first stage is divided into a relatively flat latent phase and a rapidly progressive active phase. In the active phase, there are three identifiable component parts: an acceleration phase, a linear phase of maximum slope, and a deceleration phase. (Redrawn from Friedman, 1978 .)
What happens during the last few hours of pregnancy?
The last few hours of human pregnancy are characterized by forceful and painful uterine contractions that effect cervical dilatation and cause the fetus to descend through the birth canal. There are extensive preparations in both the uterus and cervix long before this.
What are the phases of parturition?
These phases of parturition include: (1) a prelude to it, (2) the preparation for it, (3) the process itself, and (4) recovery. Importantly, the phases of parturition should not be confused with the clinical stages of labor, that is, the first, second, and third stages—which comprise the third phase of parturition ( Fig. 21-2 ). + +.
When does the cervix soften?
During the first 36 to 38 weeks of normal gestation, the myometrium is in a preparatory yet unresponsive state. Concurrently, the cervix begins an early stage of remodeling—termed softening —yet maintains structural integrity.
What is phase 1 of pregnancy?
Phase 1 of Parturition: Uterine Quiescence and Cervical Softening. Beginning even before implantation, a remarkably effective period of myometrial quiescence is imposed. This phase normally comprises 95 percent of pregnancy and is characterized by uterine smooth muscle tranquility with maintenance of cervical ...
What is a uterine contraction?
Uterine contractions are involuntary, peristaltic and intermittent. They are regular and painful in nature, enough to distract patient from her normal activities. They are controlled by nervous system and endocrine influence. Normal contractions increase in frequency, strength and duration.
Where does the contraction start?
Each contraction starts at the fundus near the cornua and spread gradually across downwards to the lower uterine segment, but usually remain stronger and last longer at the upper region of the uterus (fundus), but the peak is reached simultaneously over the whole uterus and the contraction fades from all part together.
What happens before dilatation in primp?
The cervix becomes shortened as it merges with the lower uterine segment. It takes place before dilatation in primp but in multip it occurs as the cervixis dilating. In grande multiparae complete effacement may not take place. Dilatation of the cervix: Is the widening of the external Os.
What is the upper and lower uterine segment?
By the end of pregnancy the uterus divide into two distinct poles. The lower segment develops from the isthmus, internal Os and the cervical canal. During labor the retracted longitudinal fibres in the upper segment exert a pull on the lower segment making it to stretch.
What is the dilation of the cervix?
Dilatation of the cervix: Is the widening of the external Os. Theretracted muscle fibres of the upper segment exert a pull on the weak lower segment and the cervix, making, it to dilate from a thing closed aperture to an opening large enough to permit passage of the fetal head.
How does amniotic sac function during contraction?
It ensures adequate supply of oxygen to the fetus during contraction by preventing compression of the placenta by the fetus. Rupture of Membranes: the amniotic sac should remainintact until the OS is fully dilated (end of the 1st stage) but this is not always the case.
How long does it take for contractions to increase?
They become more painful, rhythmic in nature, starts by occurring every 15-20 minutes in early labor (frequency) and increase to 2-3 minute in second stage, strength increases in intensity lasting 50-60 second in duration at the end of first stage.
What is labour in biology?
bookmarks Recommended reading. Labour (also known as parturition) is the physiological process by which a foetus is expelled from the uterus to the outside world. There are three separate stages, characterised by specific physiological changes in the uterus which eventually result in expulsion of the foetus.
What is the process of labor called?
Initiation of Labour. The exact process by which labour is initiated in humans is not fully understood. Throughout the third trimester, involuntary contractions of the uterine smooth muscle begin to occur - these are known as Braxton Hicks contractions.
What happens when the cervix is dilated?
Once the cervix is dilated the foetal head is able to descend, remaining flexed to maintain the smallest diameter possible. Second Stage. This lasts from full dilatation of the cervix until the foetus has been expelled. Uterine contractions become expulsive and this pushes the foetus through the birth canal.
What is the role of oxytocin in pregnancy?
Oxytocin is responsible for initiating uterine contractions. Throughout pregnancy it has limited action as there are a low number of oxytocin receptors and it is inhibited by relaxin and progesterone.
How does the head of a foetus move?
Once the head of the foetus reaches the perineum, it extends in order to come up and out of the pelvis. Following delivery of the head, it rotates by 90 degrees to assist with delivery of the shoulders.
What is the process of releasing oxytocin?
This is known as the Ferguson reflex.
What is the contraction of the uterine smooth muscle called?
Throughout the third trimester, involuntary contractions of the uterine smooth muscle begin to occur – these are known as Braxton Hicks contract ions.
How long does the first stage of labor last?
Latent Phase: This phase lasts for approximately 6-8 hours, achieving a cervical dilation of ~3-4 cm.
What happens in between contractions?
In between each contraction and push, the uterus relaxes and the baby recedes. At a certain point, the perineum will start to bulge and the baby’s head will become visible. This is termed crowning. Once the head is born, the shoulders and body follow with the next contraction.
Why do we use warm compresses during labor?
Warm compresses are used during labour with the intention to reduce perineal pain and increase comfort during labour. Heat promotes dilation of blood vessels, increases blood flow, and interrupts the transmission of pain. Dahlen and colleagues (2009) reported that women who received a warm compress during the second stage of labour were significantly less likely to report the pain they experienced as “bad” or as the “worst pain in my life” and had a statistically significant lower mean pain score than women who received standard care. Other studies with smaller sample sizes have supported the use of warm packs. Similarly, immersion in warm water has been supported in the literature to reduce labour pains. When considering the use of warm compresses during the first stage of labour, a review by Smith and colleagues (2018) reported that low-quality evidence exists. During the third phase of labour, heat could increase a mother’s comfort, increase endorphin and oxytocin release, and potentially allow for earlier delivery of the placenta.
How long does it take to get to stage 2 of labor?
Stage two can be divided into two phases: the latent phase and the active phase. The average duration of stage two is 50 minutes for primigravida mothers and 20 minutes for multigravida mothers.
Why are contractions longer in stage 2?
Contractions are longer and stronger in stage two, however, they are less frequent to allow the mother time to recover between each contraction. As the baby is descending through the uterus it will change its position frequently to navigate the curvature of the birth canal.
What happens when the cervix dilates?
As the cervix dilates, the mucus plug formed during pregnancy is lost and women might notice a bloody mucoid discharge.
How long does labor last?
During early labour, contractions are fairly weak, occurring 15 - 20 minutes apart and lasting ~ 30 seconds in duration.
What is abnormal labor?
Abnormal labor. Dystocia (literally difficult labor) is characterized by abnormally slow progress in labor. It is the consequence of four distinct abnormalities that may exist singly or in combination. Uterine forces that are not sufficiently strong or appropriately coordinated to efface and dilate the cervix.
What is the normal fetal attitude when labor begins?
The normal fetal attitude when labor begins is with all joints in flexion. Lie : This refers to the longitudinal axis of the fetus in relation to the mother's longitudinal axis (i.e., transverse, oblique, or longitudinal (parallel).
What is cervical effacement and dilatation?
Cervical Effacement and Dilatation. The Mechanism of Normal Labor. The definition or clinical diagnosis of labor is a retrospective one. There is no laboratory test that gives a "labor titer" or an x-ray procedure that can define the difference between the laboring and non-laboring patient.
What is the meaning of the following germs?
To understand the meaning of the following germs: Presentation, position, lie, station, effacement, di latation. To understand the phases and stages of labor. and arrest of descent.
Is the fetus a passive respondent?
For the most part the fetus is a passive respondent in the process of labor, while the mother provides the uterine forces and structural configuration of the passageway through which the passenger must travel. For a normal mechanism of labor to occur, both the fetal and maternal factors must be harmonious.
Contraction
Fundaldominant
- Eachcontraction starts at the fundus near the cornua and spread gradually acrossdownwards to the lower uterine segment, but usually remain stronger and lastlonger at the upper region of the uterus (fundus), but the peak is reachedsimultaneously over the whole uterus and the contraction fades from all parttogether.
Retraction
- Retractionis peculiar to the uterine muscles only, whereby the wave of contraction doesnot pass off entirely, but the musclefibres retain some of the contractile toneinstead of relaxing completely. Retraction assists in the progressive expulsionof the fetus by maintaining the downward pressure. As the upper uterine segmentbecomes shorter, thicker and the cavity reduces the lower uterine …
Polarity
- This isthe neuro-muscular harmony that prevails between the upper and the loweruterine segments. The two poles act harmoniously. The upper segment contractsstrongly and retracts to expel the fetus while the lower uterine segmentcontract slightly and stretches to expel the fetus. If polarity is disorganizedthe progress of labor is inhibited.
Formation of Upper and Lower Uterine Segment
- By theend of pregnancy the uterus divide into two distinct poles. The lower segmentdevelops from the isthmus, internal Os and the cervical canal. During labor theretracted longitudinal fibres in the upper segment exert a pull on the lowersegment making it to stretch. This causes the Os to dilate and become part ofthe lower segment. The upper segmen...
Show
- The lostof blood stained mucoid discharge as the cervix dilate. It is from the plug ofmucus that guards the cervical canal during pregnancy. It can be seen a fewhours before or after labour has started.
Formation of Bag of Waters
- When thelower uterine segment stretches, the chorion get detached from it and theincrease intra uterine pressure causes the bag of fluid to bulge through thedilating internal OS. The well flexed head which fix neatly into the cervix cutoff the fluid in front of the head from the one which surrounds the behindbody. This one in front is known as forewatersand the behind is known as …
Physiology of The Second Stage
- Contractionand Retraction continue: During this stage the contraction are more severe,stronger and expulsive, occurring more frequently (about 1-2mins) and of longerduration about 60sec or more. The fetal head press and stretches the vaginawhich in-turn stimulates uterine action. Also the membranes help the fetus tobe in close contact with the cervix, the upper segment gets muc…
Physiology of Third Stage
- Contractionand Retraction Continue: As the upper segment becomes thicker and smaller afterthe birth of the baby the placenta site also become reduced this makes theplacenta to buckle off the uterine wall and separate. The placenta drops intothe lower uterine segment or the vagina, followed by the membranes whichstripped off the uterine wall by the traction of the descending …
Methods of Placental Separation
- There aretwo methods of separation and expulsion of the placenta. Shultze Method: 80%: This isthe most common method. Inthis method separation starts from the centre of theplacenta and with the aid of Retroplacenta clot the placenta drop into thelower uterine segment or into the vagina. During delivery the fetal surfaceappears first at the vulva followed by the membranes. T…