Stages of Labor Overview

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Questions and Answers

What is the average duration of the second stage of labour for a multipara?

2 hours

30 minutes

1 hour (correct)

3 hours

What is the maximum duration for the third stage of labour before it is considered abnormal?

30 minutes (correct)

45 minutes

1 hour

15 minutes

During the active phase of labour, how frequently does cervical dilatation typically occur?

0.5 cm/hour

2 cm/hour

1 cm/hour or more (correct)

1.5 cm/hour

What defines the propulsive phase of the second stage of labour?

Starts at full dilation and ends with the descent to the pelvic floor Signup and view all the answers

What characterizes the upper uterine segment during labour?

Is mainly concerned with contraction and retraction Signup and view all the answers

What is the role of polarity during uterine contractions in labour?

Favors effective contractions and progress of labour Signup and view all the answers

What primarily takes place during the expulsive phase of the second stage of labour?

Maternal bearing down efforts Signup and view all the answers

Which statement about contraction and retraction of the uterus is correct?

All parts of the uterus contract simultaneously Signup and view all the answers

What is the retraction ring formed by during labor?

The contraction of the upper uterine segment Signup and view all the answers

What happens to the cervical canal during effacement?

It is pulled upwards and merges into the lower uterine segment Signup and view all the answers

What marks the process of cervical dilatation?

The cervix opening from tightly closed to 10 cm Signup and view all the answers

What occurs to the operculum during the early stages of labor?

It is lost due to cervical dilatation Signup and view all the answers

In the context of forewaters and hindwaters, what is true?

Forewaters are formed as the sac of fluid bulges into the internal os Signup and view all the answers

What is the role of the lower uterine segment during labor?

To stretch and thin to accommodate the fetus Signup and view all the answers

How is cervical effacement visually identified?

By the thinning of the cervix as it merges with the uterus Signup and view all the answers

What is the expected cervical dilatation at term?

10 cm Signup and view all the answers

What is general fluid pressure during labor?

Pressure exerted on the fluid that is equalized throughout the uterus and fetal body Signup and view all the answers

When is the optimal time for the membranes to rupture spontaneously?

At the end of the first stage of labor after full dilation Signup and view all the answers

What term describes how the fetal head applies force to the cervix during contractions?

Fetal axis pressure Signup and view all the answers

What physiological change occurs as the fetal head descends during labor?

Displacement of the bladder and rectum Signup and view all the answers

How does fetal axis pressure impact the presenting part of the fetus?

It promotes smaller presenting diameters Signup and view all the answers

What triggers the Ferguson reflex during labor?

Pressure from the presenting part stimulating nerve receptors Signup and view all the answers

What happens to the fetal head during each contraction prior to birth?

It visibly advances at the vulva and recedes between contractions Signup and view all the answers

What occurs immediately after the fetal head is born during the second stage of labor?

The shoulders and body follow with the next contraction Signup and view all the answers

What is the first movement that is required for the birth of the newborn?

Descent Signup and view all the answers

Which diameter becomes the leading part as the fetal head descends in labor?

Suboccipitobregmatic diameter Signup and view all the answers

During which movement does the fetal head extend and pivot around the pubic bone?

Extension of the head Signup and view all the answers

What allows the occiput to lead and rotate during descent?

Pressure from the pelvic floor Signup and view all the answers

What is the purpose of engagement in the cardinal movements of labor?

To align the fetus with the pelvis Signup and view all the answers

Which of the following movements occurs immediately after the fetal head meets resistance?

Flexion Signup and view all the answers

What happens during the restitution phase of labor?

The neck untwists to align the head with the shoulders Signup and view all the answers

Which of the following movements follows after the fetal head has crowned?

Extension Signup and view all the answers

What occurs during internal rotation of the shoulders in relation to the pelvic outlet?

The shoulders rotate in the anteroposterior direction to align with the pelvic outlet. Signup and view all the answers

What initiates the third stage of labour?

The expulsion of the placenta and membranes. Signup and view all the answers

When does retraction of the uterine muscle fibers occur during the third stage of labour?

Immediately after the birth of the baby. Signup and view all the answers

How long does the third stage of labour generally last?

Between 5 and 15 minutes. Signup and view all the answers

What happens when the uterine fundus is just below the level of the umbilicus?

The placenta begins to detach from the uterine wall. Signup and view all the answers

Which statement about the separation of the placenta using the Schultze method is accurate?

Separation usually begins centrally, forming a retroplacental clot. Signup and view all the answers

What role does the lateral flexion of the spine play during birth?

It assists in delivering the shoulders after the head. Signup and view all the answers

What causes the veins in the uterine layer to become tense and congested during the third stage of labour?

Pressure exerted by the contracting uterine muscle fibers. Signup and view all the answers

Study Notes

Stages of Labor

The first stage of labor is characterized by cervical dilation and effacement.
The active phase of the first stage of labor is marked by cervical dilation at a rate of 1cm/hour or more.
The second stage of labor starts with full cervical dilation and ends with the delivery of the fetus.
The propulsive phase of the second stage of labor begins with full dilation and ends with descent of the presenting part onto the pelvic floor.
The expulsive phase of the second stage is characterized by maternal bearing down efforts and culminates in the delivery of the baby.
The third stage of labor begins after the delivery of the fetus and ends with expulsion of the placenta and membranes.
The fourth stage of labor begins with the expulsion of the placenta and ends after two hours.

Uterine Action: First Stage of Labor

Fundal dominance: Each uterine contraction starts in the fundus near one of the cornua and spreads downwards.
Polarity: The upper pole of the uterus contracts strongly and retracts to expel the fetus, while the lower pole dilates to facilitate expulsion.
Contraction and Retraction: Contractions allow for the expulsion of the baby, and retraction reduces the area of the uterus.

Formation of Upper and Lower Uterine Segments

The upper uterine segment, formed from the body of the fundus, contracts and retracts, pushing the baby down.
The lower uterine segment, formed from the isthmus and the cervix, stretches and dilates to accommodate the descending fetus.

Retraction Ring

The retraction ring forms between the upper and lower uterine segments as the upper segment contracts and the lower segment thins out.

Cervical Effacement

Effacement is the thinning of the cervix as its canal is drawn upwards into the lower uterine segment.
Effacement proceeds from above downward, with the internal os being drawn upwards by the retracted upper uterine segment.

Cervical Dilatation

Dilatation is the widening of the cervical os from a tightly closed aperture to a size that allows the passage of the fetal head.
Full dilatation at term is approximately 10cm.

Show

The show is a blood-stained mucoid discharge that may be seen before or within a few hours after labor starts.
It arises from the ruptured capillaries in the parietal decidua where the chorion becomes detached from the dilating cervix.

Formation of Forewaters

Forewaters are the amniotic fluid located in front of the presenting part of the fetus.
It is formed when the chorion becomes detached from the stretching lower uterine segment and the increased intrauterine pressure causes the fluid to bulge downwards.

General Fluid Pressure

When the membranes remain intact, the pressure of the uterine contractions is equalized throughout the uterus and the fetal body due to the incompressibility of fluid.

Rupture of Membrane

The optimal time for membranes to rupture spontaneously is at the end of the first stage of labor after the cervix is fully dilated.

Fetal Axis Pressure

Fetal axis pressure is the force transmitted by the contracting fundus to the upper pole of the fetus, down the long axis of the fetus, and then applied by the presenting part to the cervix.

Uterine Action: Second Stage of Labor

Contractions become stronger and longer but less frequent, allowing for recovery periods.
Spontaneous membrane rupture usually occurs towards the end of the first stage or during transition into the second stage.
Maternal effort and fetal axis pressure increase flexion of the fetal head, which facilitates quicker progress and reduces trauma.
The Ferguson reflex is triggered when the presenting part stimulates nerve receptors in the pelvic floor, resulting in the urge to push.

Soft Tissue Displacement

The descending fetal head displaces pelvic soft tissues: anterior bladder, posterior rectum, levator ani muscles, and perineal body.

Cardinal Movements

Engagement: The biparietal diameter of the fetal head passes through the pelvic inlet.
Descent: The fetal head descends through the birth canal, facilitated by uterine contractions and maternal effort.
Flexion: The fetal head flexes as it meets resistance, substituting the shorter suboccipitobregmatic diameter for the larger occipitofrontal diameter.
Internal Rotation: The occiput rotates anteriorly towards the symphysis pubis as the head meets the resistance of the pelvic floor.
Extension: The head extends, pivoting on the suboccipital region around the pubic bone, leading to delivery of the face and chin.
Restitution: The fetal head untwists slightly, correcting the twist caused by internal rotation.
Internal Rotation of Shoulders: The shoulders rotate to lie in the anteroposterior diameter of the pelvic outlet.
Lateral Flexion: The anterior shoulder passes under the pubic symphysis and the posterior shoulder over the perineum, followed by the rest of the body.

Third Stage of Labor: Mechanisms

Separation: The placenta detaches from the uterine wall due to uterine contractions, retraction of uterine muscle fibers, and a retroplacental clot forming behind the placenta.
Descent: The placenta descends into the lower uterine segment.
Expulsion: The placenta is expelled from the vagina, usually within 5 to 15 minutes.
Control of Hemorrhage: Retraction of uterine muscle fibers and the release of clotting factors help control bleeding from the placental site.

Schultze Method

This method describes when the central part of the placenta separates first, resulting in a retroplacental clot.

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Description

This quiz covers the stages of labor, detailing cervical dilation, the phases of labor, and the actions of the uterus during these stages. Test your knowledge on the first, second, third, and fourth stages of labor, along with their characteristics and significance in childbirth.