Parturition

Question 1

Describe the relationship between cervical effacement and cervical dilation

Answer 1

Effacement is thinning/flattening of the cervix (the thinner the membrane, the more % effaced it is, ideally you want a 100% effaced cervix)

As the cervix becomes softer (cervical ripening) and thinner, it becomes easier to dilate/open.

Question 2

Prostaglandin synthesis increases in response to what?

Answer 2

Relative fall in progesterone when comparing it to levels of estrogen, either by progesterone dropping or an increase in estrogen

Question 3

When does the first stage of labour end?

Answer 3

When the cervix is fully dilated at 10 cm

Question 4

Reasons for failure to progress can be divided into separate categories. List the categories and give an example of each

Answer 4

Power - inadequate contractions
Passage - abnormally shaped pelvis
Passenger - large-sized fetus, number and position

Question 5

What is labour progression plotted on?

Answer 5

Partogram

Question 6

What is the diameter of the pelvic inlet? How might the diameter change during pregnancy?

Answer 6

11cm, during pregnancy there is softening of the ligaments surrounding the pelvic inlet to increase the diameter to facilitate passage of the baby

Question 7

What is considered an ideal orientation for the fetus to be in delivery and why?

Answer 7

Longitudinal lie, cephalic presentation (part of the fetus adjacent to pelvic inlet) with the head flexed so that the vertex (between parietal eminences and anterior-posterior fontanelles) is the presenting part.

Question 8

What questions could you ask in regards to contractions to determine whether an individual is in labour?

Answer 8

The intensity and frequency of contractions

Question 9

What is special about the way uterine muscles contract in labour compared to normal muscle contractions?

Answer 9

Brachystasis; myometrial fibres only partially relax and cannot return to their original size - therefore there is a permanent shortening of the muscle fibres after each contraction. This gradually increases the pressure within the uterus (as it’s becoming smaller) to drive the fetus out through the birth canal.

Question 10

What features of the cervix would you assess to determine whether the patient is in active labour?

Answer 10

The dilation, effacement (how thin and pliable) and how short it’s become

Question 11

Describe the mechanism by which the force of contractions is increased during labour? Other than contractions, what else does this mechanism assist when giving birth?

List 4 things that can aid this process

Answer 11

Ferguson reflex. Stimulated by contractions which are detected by sensory receptors in the cervix and vagina. These sensors send afferent info to the hypothalamus to increase oxytocin release. The oxytocin acts directly on the uterus to increase the FOC and increases the prostaglandins circulating to further increase the frequency.

Contractions lead to more pressure, and thus the cycle is positive feedback until the pressure is released when the baby passes through. This helps the cervix dilate and ruptures the amnion (breaking the water).

This can be aided by…

1. Opening the pelvis to 55 degrees
2. A water environment reduces gravity.
3. Anything to increase pressure on the cervix like standing upright
4. Oxytocin is released with parasympathetic stimulation so it’s important to be in a calm relaxing environment

Question 12

What happens to the mother’s uterus after the fetus has been expelled and what can be given if it’s not happening as quickly as it should?

Answer 12

The uterus continues to contract and shrink, directing the placenta towards the cervix. Contractions of the uterine muscle (given that they’re big and becoming smaller) are also squashing arteries in the endometrium, muscle fibres also retract and seal off the vessels. As a result, blood can’t drain into the maternal bloodstream, completing the separation. Shutting off blood supply to the placenta also prevents maternal hemorrhage

Can give synthetic oxytocin to increase/facilitate these contractions which helps reduce the risk of maternal hemorrhage (side note: the placenta can also be manually pulled out)

Question 13

What is type 1, 2, 3 and 4 genital mutilation? Why would it be carried out?

Answer 13

Type 1: partial or total removal of the clitoris
Type 2: When the clitoris or labia minora is partially or totally removed with or without removal of labia majora
Type 3: infibulation; narrowing the vaginal opening by creating a ‘covering seal’ by cutting or repositioning the labia minora or majora
Type 4: all other harmful procedures to the female genitalia for non-medical purposes

Cultural reasons i.e right of passage, etc

Question 14

At which weeks must the baby be delivered for the following?

a) spontaneous abortion
b) pre-term
c) term

Answer 14

a) before 24 weeks
b) before 37 weeks
c) 37-42 weeks

Question 15

What happens in the first stage of labour and what are the two phases?

Answer 15

It’s the interval between the onset of labour and full cervical dilation and creation of the birth canal through expansion of the soft tissues (cervix, vagina and perineum), and the cervix must retract anteriorly.

Latent phase: onset of labour with slow cervical dilation to ~4cm, contractions tend to be becoming more regular and increasing in intensity. Progresses to the…
Active phase: faster rate of cervical change, 1-1.2 cm/hour and regular uterine contractions

Question 16

What marks the end of the second and third stages of labour? How long does each of them typically take?

Answer 16

Second: delivery of the fetus, usually up to 1 hr but 2 allowed if it is the first pregnancy

Third: delivery of placenta + membranes, usually 5-15 min but can go up to an hour

Question 17

Which scan helps determine whether the mother is having single or multiple pregnancies and when is it done?

Answer 17

The dating scan around week 12

Question 18

How is the method of delivery influenced when the baby is in ‘transverse lie’ or has a breech?

Answer 18

The mother may choose a cesarian section or a procedure where the baby is externally turned around 37 weeks

Question 19

Which bones make up the pelvis?

Answer 19

Sacrum, coccyx and two hipbones (ischium, ileum and pubis)

Question 20

When can babies with face cephalic presentation be delivered vaginally?

Answer 20

If they are in the mento-anterior position (not mentoposterior)

Question 21

What does it mean if there is podalic presentation? What is this ‘classed as’ and what are the three types?

Answer 21

Podalic presentation means the buttocks sitting in the pelvic inlet (instead of the head). This is classed as a breech

1. Frank breech: When hips are flexed but knees extended
2. Full breech: hips and knees flexed
3. Single footing breech: foot presents out of the cervix

Question 22

What is meant by the term ‘cervical ripening’ and what is it triggered by? Why is it necessary?

Answer 22

Since the cervix has always been tough and thick (collagen) to retain the fetus, it must undergo a structural change to soften and dilate. This process is called ‘cervical ripening’… Prostaglandins E2 and F2x trigger

1. A reduction in collagen
2. And an increase in glycosaminoglycans to reduce the aggregation of the collagen fibres (so the collagen bundles loosen and the cervix softens).

Question 23

Describe the structural changes of the myometrium to expel the fetus

Answer 23

During pregnancy, the smooth muscle cells undergo hypertrophy so that by the end of the pregnancy the myometrium has become much thicker. There is also increased glycogen within the muscle, which is important in generating the force required to expel the fetus

Question 24

Describe how uterine contractions change throughout pregnancy and in labour and which hormones are involved?

Answer 24

They begin with a low force every 30 min. Later, contractions become less frequent but more intense

In labour: contractions become more frequent and forceful due to two hormones:

a) prostaglandins increase intracellular calcium in smooth muscle cells (force)
b) oxytocin lowers the threshold that APs may be triggered (frequency)

Question 25

What are prostaglandins and where are they synthesized? What controls their production?

Answer 25

They are biologically active lipids that act as local hormones. They can be produced by most tissues in the body, including the endometrium. Controlled by the estrogen: progesterone ratio. If there’s more progesterone, prostaglandin synthesis decreases (and increases vice versa)

Question 26

What is oxytocin, where is it secreted from and what controls its secretions and effects on smooth muscle?

Answer 26

A peptide hormone secreted from the posterior pituitary (controlled by the hypothalamus).

Its effects are controlled by a high estrogen: progesterone ratio

Question 27

How does the influence of oxytocin on the myometrium change throughout pregnancy?

Answer 27

At first, oxytocin is inhibited during pregnancy due to progesterone and the low levels of oxytocin receptors found in the myometrium.

However, at 36 weeks progesterone levels fall (changing the ratio), this change results in more oxytocin receptors being produced in the myometrium - so it is more susceptible to the pulsatile release from the pituitary

Question 28

Why might artificial initiation of labour be necessary? Name four maternal reasons and three fetal ones

Answer 28

Maternal:

1. Severe preeclampsia
2. Recurrent antepartum hemorrhage
3. Pre-existing disease (like diabetes)
4. Social

Fetal:

1. Prolonged pregnancy (over term date)
2. Intrauterine growth restriction
3. Rhesus disease

Question 29

What is the Bishop’s score used for?

Answer 29

Used by midwives and doctors to asses the ‘readiness’ of the cervix. The more effaced and dilated the cervix, the higher the Bishop’s score, the easier the vaginal passage will be

Question 30

List three things you can give to induce labour and the pros and cons of each if applicable

*list 5 complications for the nonhormonal method

Answer 30

1. Prostaglandins (gel, tablet or pessary/in the vagina) ripen the cervix. They reduce the risk of cesareans when compared to using oxytocin alone but miscalculating the dose can hyperstimulate the uterus causing distress on the fetus
2. Oxytocin (IV or synthetic) post SROM or amniotomy. It requires constant fetal monitoring and careful dose titration in accordance with the frequency and strength of contractions
3. Amniotomy: releasing fluid from the amniotic sac to induce labour. Complications include; cord prolapse, infection, failure (to induce efficient contractions), bleeding from vasa praevia, amniotic fluid embolism, etc

Question 31

When and why would you use cardiotocography?

Answer 31

Monitors the uterine contractions (bottom half) and the fetal HR (top half). A CTG can be used if there are concerns about how labour is progressing and to diagnose any problems

Question 32

Name two specific things that happen during the second stage of labour

Answer 32

Delivery of the fetus

• The presenting part appears in the birth canal
• Active contractions increase in strength, duration and frequency and the mother may feel the need to push/bear down

Question 33

What happens to the fetal head as labour progresses into the second stage?

Answer 33

It becomes flexed to reduce the diameter of the presenting part and rotates internally

Question 34

What are some complications if the fetus passes through too quickly or is very large? How might this be prevented?

Answer 34

Risk of tearing the perineum. May perform an episiotomy (making a cut in the perineum) to prevent this

Question 35

What is ‘crowning’?

What needs to happen so that the baby’s shoulders can be delivered?

Answer 35

When the baby’s head reaches the vulva and remains visible without slipping back in

To deliver the shoulders (has the widest diameter) it must pass through the pelvic outlet transversely, so the baby’s head must externally rotate and extend to line the shoulders transversely

Question 36

Name six analgesics that can be used during labour and briefly describe each

Answer 36

1. Paracetamol
2. Entonox: 50/50 Oxygen/NO; inhaled, effective during the peak of contractions
3. Pethidine; opiates, may cause nausea (50% effective in labouring women, takes 15-20 min to work.)
4. Pudendal block
5. Epidural (small catheter with local anesthetic and opium mix)
6. Spinal anesthetic; useful for theatre intervention (like a cesarian)

Question 37

What is one criterion for forms of ‘operate delivery’ to be offered and what are two available methods? Are there any other interventions typically offered in conjunction with forms of an operate delivery?

Answer 37

The baby must be in the appropriate position and descended far enough

1. Forceps: Woman pushes and obstetrician does 3 attempts. Usually, woman has a spinal anesthetic in case there ends up being a need for a cesarian
2. Vacuum extraction; cup on baby’s head to extract

Question 38

Briefly describe how a cesarian section works, how many types are there and what differentiates them? Briefly describe when you would perform types 1 and 4

Answer 38

An incision is made in the mother’s abdomen, the head is delivered first while an assistant applies fundal pressure to the top of the uterus. There are four types that depend on the urgency to deliver

1. There is an immediate risk of life (baby or mother)
2. Elective section, arranged at a date/time suited for surgeon and woman prior to her going into labour to prevent any problems during labour (i.e having a large baby, known to have multiple pregnancies, known problems with her pelvis or uterus, or had a cesarian before)

Question 39

What defines a postpartum hemorrhage and how common are they? What differentiates a primary and secondary one?

What defines a major obstetric hemorrhage and how many ml must be lost for clinical significance?

Answer 39

It’s bleeding from the genital tract of >500 ml after delivery of the infant and occurs in ~5%.
Primary: within 24 hours
Secondary: Between 24 hours and 6 weeks

1L must be lost to be clinically significant. Obstetric hemorrhage: >1500 ml lost

Question 40

What is the Apgar scoring system used for and how does it work?

Answer 40

After the baby is born the Apgar scoring assesses 5 domains; the baby’s activity, pulse, grimace (reflex irritability), appearance (skin colour) and respiration. Each is scored max 2 for a max total score of 10.

Score: >=7, normal healthy baby
Any score <7 may need immediate intervention

Further Apgar scores are done after the child is born to ensure they are still well or showing signs of improvement

Question 41

What can happen if the analgesic pethidine is given close to the delivery time? Can it be reversed?

Answer 41

Can cause respiratory depression of the baby if it’s given close to the delivery time, but can reverse this with naloxone