Mechanisms of labour (OSCE) Flashcards
Which is largest diameter of pelvic inlet
Transverse - 13cm
What is largest diameter of pelvic outlet
AP - 13cm
First stage of mechanism of labour
Decent into pelvis
In a cephalic descent, what two orientations can the head be in
Left or right occipital transverse position
occiput is facing left of right side of mum
Descent of baby is encouraged by:
Abdominal muscle tone
Braxton hicks and fundal dominance in contractions
Amniotic fluid pressure
Definition of engagement in mechanisms of labour
Largest diameter of fetal head descends into pelvis
Engagement may be defined as the midwife by assessing the patient to be x?
Fetal head is 3/5th’s palpable or less
Stage of labour after descent
Engagement
Stage of labour after engagement
Flexion
Stage of labour after flexion
Internal rotation
Stage of labour after internal rotation
Crowning
Stage of labour after crowning
Extension of presenting part
Stage of labour after extension of presenting part
External rotation and restitution
What causes flexion to happen
Fundal dominance in contractions of the uterus flexes baby’s head, reducing fetal head circumference
Why is flexion important in labour
To reduce diameter of head (9.5cm in sub- occipitobregmatic)
Occipital angle changes during internal rotation
90 degrees
Fetal head to rotate from the left or right occipito-transverse position a total of 90-degrees, to an occipital-anterior
Crowning definition
Widest diameter of fetal head passes through narrowest part of pelvis. Head visible at vulva and does not retreat between contractions
During extension of the presenting part, what part of the fetal head leaves what part of the pelvis
The occiput slips under the suprapubic arch - allowing head to extend
Baby is in occiput anterior position (OA)
