Mechanisms of labour (OSCE)

Question 1

Which is largest diameter of pelvic inlet

Answer 1

Transverse - 13cm

Question 2

What is largest diameter of pelvic outlet

Answer 2

AP - 13cm

Question 3

First stage of mechanism of labour

Answer 3

Decent into pelvis

Question 4

In a cephalic descent, what two orientations can the head be in

Answer 4

Left or right occipital transverse position

occiput is facing left of right side of mum

Question 5

Descent of baby is encouraged by:

Answer 5

Abdominal muscle tone
Braxton hicks and fundal dominance in contractions
Amniotic fluid pressure

Question 6

Definition of engagement in mechanisms of labour

Answer 6

Largest diameter of fetal head descends into pelvis

Question 7

Engagement may be defined as the midwife by assessing the patient to be x?

Answer 7

Fetal head is 3/5th’s palpable or less

Question 8

Stage of labour after descent

Answer 8

Engagement

Question 9

Stage of labour after engagement

Answer 9

Flexion

Question 10

Stage of labour after flexion

Answer 10

Internal rotation

Question 11

Stage of labour after internal rotation

Answer 11

Crowning

Question 12

Stage of labour after crowning

Answer 12

Extension of presenting part

Question 13

Stage of labour after extension of presenting part

Answer 13

External rotation and restitution

Question 14

What causes flexion to happen

Answer 14

Fundal dominance in contractions of the uterus flexes baby’s head, reducing fetal head circumference

Question 15

Why is flexion important in labour

Answer 15

To reduce diameter of head (9.5cm in sub- occipitobregmatic)

Question 16

Occipital angle changes during internal rotation

Answer 16

90 degrees

Fetal head to rotate from the left or right occipito-transverse position a total of 90-degrees, to an occipital-anterior

Question 17

Crowning definition

Answer 17

Widest diameter of fetal head passes through narrowest part of pelvis. Head visible at vulva and does not retreat between contractions

Question 18

During extension of the presenting part, what part of the fetal head leaves what part of the pelvis

Answer 18

The occiput slips under the suprapubic arch - allowing head to extend

Baby is in occiput anterior position (OA)