Understanding the physiological process of a breech birth
The following pictures show the way a breech baby wiggles her way through a mother’s pelvis when mum is upright (e.g. kneeling or hands/knees), and the signs a breech birth attendant looks for to tell if this process needs help or not. Learn more at Breech Birth Network study days, with presentations by midwives and obstetricians actively involved with breech practice and research.
A breech baby may engage before labour, or may not engage until after her mother’s cervix is fully dilated.
Some midwives feel engagement with the back on one side or another may be ideal. (See Jane Evans‘s ideas on this, on Rixa Freeze’s blog.)
I am happy for the back to be on either side, and these pictures depict the birth of a baby whose legs are extended (frank breech), with her back on her mother’s left.
Descending LST, anterior buttock leading
The breech typically descends with the sacrum transverse, anterior buttock leading. On vaginal examination, this will feel asynclitic – this is normal for breech.
Maternal movement assists this process in the same way it assists cephalic descent.
The buttocks will be born by lateral spinal flexion (wiggling the bum from side to side).
Anterior buttock rumping
The anterior (maternal front) buttock is born first, followed by the baby’s anus (usually squirting a thick glob of meconium) and the posterior buttock.
The sacrum will soon rotate to sacro-anterior (‘tum to bum’ – the baby’s rear should be in line with the mother’s front). If rotation is tending toward sacro-posterior, this may be an indication for intervention (to gently encourage sacro-anterior rotation).
Birth of the extended fetal legs
Baby’s legs seem to stretch forever, but will be born spontaneously as long as there is descent with each contraction. If one leg slips down before the other, this may indicate that full internal rotation has not occurred, and help with the arms may be needed.
“If it progresses, wait and see.” – Mary Cronk
Birth of the umbilicus
After baby’s legs flop down, you will have a clear view of the umbilicus and may even be able to see the baby’s heart rate from her chest. Do not touch the umbilicus, but observe: colour, tone, flexion/movement.
Reassuring sign: If you observe cleavage (the sternal crease) on the baby’s chest, you know the arms are in front and should be born in the next contraction.
Indication for intervention: If full rotation has not occurred, and progress stops, you will need to assist with the birth of the arms.
Rotation to drop the anterior arm below the pubic arch
As the head engages, baby rotates slightly to release one arm below the pubic arch, then rotates the other direction to release the other arm.
Occasionally, arms are born together without rotation.
Birth of the fetal arms
Baby should be ‘tum to bum’ following the birth of the arms, to enable the birth of the after-coming head.
Unflexed head obstructed in pelvis
A well-flexed head will pass easily through the pelvis.
Commonly, women experience an urge to lower their bottoms to the surface on which they are kneeling (e.g. bed, floor mat, etc.) This maintains and promotes flexion in the baby’s body and should not be interrupted.
Flexed head passing through pelvis
Babies have often been observed doing a ‘tummy crunch,’ spontaneously pulling their knees up into a fetal position. This also promotes flexion and helps the head to be born.
If progress arrests – no descent with the next contraction – help to flex the head is indicated, especially if baby’s tone and colour are not ideal.
Want to learn more?
See the mechanisms in a series of birth photos on Midwife Mutiny blog.
More on Mechanisms from this blog.
Excellent sources of information:
Evans, Jane. (2012). Understanding physiological breech birth. Essentially MIDIRS, 3(2), 17-21.
Evans, Jane. (2012). The final piece of the breech birth jigsaw? Essentially MIDIRS, 3(3), 46-49.
Frye, Anne. (2004). Holistic Midwifery, Volume II, Care of the Mother and Baby from the onset of Labour through the First Hours after Birth. Labrys Press. (available here)