Chapter 1 - The Pelvis, Fetal Skull & Mechanism of labour

Question 1

Positon:

Answer 1

The reference point that is an easily definable point on the periphery of the presentation usually a bony prominence to fixed points of the maternal pelvis

Question 2

What are the different positions?

Answer 2

‘The denominator for the vertex is the occiput (O)’
For the face, the denominator is the chen (mentum) (M)
For the shoulders , the acromion (A)
For breech, the sacrum (S)

Question 3

What are the 4 p’s

Answer 3

Sucessful labour includes a combination of efficient uterine contractions ( POWER), an adaquate roomy pelvis (PASSAGE), an an appropriate fetal size ( PASSENGER)

Question 4

Labour

Answer 4

The series of events whereby the contents of the gravid uterus, the fetus, amniotic fluid, placenta and membranes are expelled from the pregnany women

Question 5

What are the 9 bones in the fetal skull

Answer 5

occipital, two parietal, two frontal, two temporal, sphenoid and ethmoid

Question 6

What are sutures

Answer 6

The bones in the fetal skull are held together by membranes also called sutures which permit their movement and overlap during labour

Question 7

What is moulding

Answer 7

Moulding is the proces whereby the anatomical relationship between the cranial bones is changed as a response to external pressure and forces

Question 8

Flexion

Answer 8

The degree of flexion of the fetal head during labour depends on which regions of the fetal skull is presenting

Question 9

Types of flexion

Answer 9

The suboccipitobregmatic ( fully flexed vertex) and The submentobregmatic ( face) are the narrowest diameters at 9.5cm each

The widest part diameter is 13.5 which is the mento-vertical of a brwo presenation

Suboccipito-frontal (10.5cm) and occipito-frontal (11.5cm) both deflexed vertex presentation

Question 10

Caput succddaneum

Answer 10

Refers to the sucutaneous sero haematic extravasation that usually occurs in labour that occurs when the vertex is the presenting part.
Usually resolves within a few days after birth.

Preterm prelabour ruputure of the membranes can usually lead to this.

Question 11

Initation of labour

Answer 11

Phase 0, : uterine mymoetrial activity is inactive it is believed that this is due to action of progesterone

Phase 1 : Activation of uterine activity occurs by uterotrophins such as oestrogen and through increased expression of contraction-associated proteins

Phase 2 : Stimulation when prostaglandins and oxytocin acton the activated myometrium

Phase 3: Postpartum involation

During pregnancy the uterus grows under the action of oestrogen : growth ceases towards the end of pregnancy

Question 12

Lie

Answer 12

The relationship of the fetal longitudinal axis to that of the uterus

Either Longitudinal, Transverse or Oblique

Question 13

Causes of transverse

Answer 13

prematurity, multipartity, mulitple pregnancy, placenta praevia, a fundal placenta, polyhydraminos, uterine fibromatas, congenital uterine anomalies,intrauterine fetal death and extrauterine massess obstructing the birth canal e.g. large ovarian cyst

Question 14

Risk factors of transverse position for fetus

Answer 14

A lower pH
Lower birth weight
More likely to sustain birth trauma
More likely to develop severe acidiosis

Question 15

Presentation

Answer 15

The presenting part of the fetus is the lowermost part of the fetal body within the birth canal that can be felt during vaginal examination

Question 16

Examples of presentation

Answer 16

Vertex
In transverse or oblique lies, the PP is usually the shoulder or rarely the umbilical cord

In breech presentation, the description og the presenting part depends on the relationship of the lower extremities to the fetal hips

Question 17

Types of breech

Answer 17

With frank breech (extended breech) both thighs are flexed and both knees are extended this is the most common

With flexed (complete breech) when both thighs and knees are flexed

Footling (incomplete breech) when one hip is flexed whilst the other is extended

Question 18

What is compound presentation?

Answer 18

refer to more than one part of the fetal body presenting e.g. hand and vertex

Question 19

What is Attitude?

Answer 19

This refers to the chracteristics posuture that the fetus adopts during the last week of pregnancy e.g. arms folded

Question 20

When can the uterus be palpated?

Answer 20

From 12 weeks gestation

the uterine fundus reaches the level of the xiphisernum by 36 weeks

Question 21

What are the first 2 manoeuvres of labour

Answer 21

1) uterine fundal area is palpated to determine what part of the fetus is occupying the fundus. E.G. Head round and ballotable and breech is softer
2) lateral walls of uterus felt to determine on which side is the fetal back, large and firm.

Question 22

What are the final manoeuvres of labour?

Answer 22

3) gentle grip of thumb and fingers placed on the area over the symphysis pubis to determine what part of the fetal head is lying over the pelvic inlet and the amount of that PP that is palpable abdominally
4) the amount of the fetal head that is palpable outside of the pelvis in fifths. When all the fetal head is felt it is 5/5 palpable, When the fetal head is engaged usually 2/5th palpate, when deeply engaged its 0/5 palpable

Question 23

Two types of pelvic examination?

Answer 23

Speculum

Digital vaginal examination

Question 24

What should be noted sterile speculum examination

Answer 24

Inspection of vulva & vagina
the presence/absence of any liquor, look or discharge
Inspection of the cervix to establish length, thickness and position

Question 25

What should be noted during digital VE?

Answer 25

Bishop score status of the cervix

Question 26

Cervical effacement

Answer 26

Determined by assessing length of the cervix from the external to internal os

Question 27

Cervical position

Answer 27

Location of Cervix in relation to maternal pelvis

From posterior to mid position to anterior

Question 28

Cervical consistency

Answer 28

Ranges from firm to soft
Junction between fetal membranes and decide breaks down and an adhesive protein - fetal fibronectin enters vaginal fluid
Clinical predictor of about to happen delivery

Question 29

Identify position of presenting part

Answer 29

Identifying bony sutures of the fetal head and following the suture until it leads to a fontanelle and then indentifying sutures radiating from it

Question 30

Two stages of labour

Answer 30

Latent phase - cervical dilation up to 4cm

Active phase- 4cm and onwards full effacement

Question 31

Engagement

Answer 31

Biapare

Question 32

Engagement

Answer 32

Biaparietal diameter of the fetal head enters the true pelvis

Question 33

Decent

Answer 33

Downward movement of the fetal head in the pelvis

The number of 5ths of the presenting part still palpable above the pelvis and by the station

Question 34

Flexion

Answer 34

Uterine contractions cause flexion of the fetal head forwards as it is pressed against the lower segment of the uterus

Question 35

Internal rotation

Answer 35

Gradual turning of fetal head
Usually enters the pelvis with the sagittal sutures in the transverse
Occiput turns to be behind the symphysis pubis
PRE TERM labour labour may profession without internal rotation of fetal vertex

Question 36

Extension

Answer 36

The head is delivered through the maternal vaginal Introits by extension from the flexed position
Occiput and then further extension the vertex, the bregma, the forehead, nose, mouth and finally chin

Question 37

Extension rotation ( restitution)

Answer 37

Having delivered with the sagittal suture vertical and the occiput anterior the delivered fetal head returns to the position it occupied in the vagina
E.G. LOA, the head will ‘restitute’ to the left

Question 38

Extension rotation ( restitution) final part

Answer 38

this is followed by the complete rotation of the sagittal suture to the transverse position so that the shoulders align in the anterior posterior diameters of the pelvic outlet facilitating their passage

Question 39

Extension rotation ( restitution) Example

Answer 39

One shoulder will lie behind the symphysis pubis and the other will be posterior infront of the sacral promontory

Question 40

Explusion

Answer 40

The rest of fetal body is delivered
Birth of the baby is completed by the anterior shoulder first then by lateral flexion and then posterior shoulder and finally remainder of the torso