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.
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 – the anal cleft is closest to the maternal sacrum. 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 with the next contraction or active maternal effort between contractions. If not, you need to help.
Indication for intervention: If full rotation has not occurred by the time the nipple line is visible, or progress stops for >90 seconds at any point, you will need to assist with the birth of the arms.
Rotation to drop the anterior arm below the pubic arch
In most breech births, the arms will be born spontaneously with the baby’s torso in a sacrum-anterior position (‘tum to bum’).
Occasionally, 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.
Birth of the fetal arms
Baby should be ‘tum to bum’ following the birth of the arms, and the head should be aligned in the pelvis in an occipit-anterior position.
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,’ or full body flexion recoil, spontaneously pulling their knees up into a fetal position. This also promotes flexion and helps the head to be born.
Note: A compromised baby will not do this, and you will need to assist more, and sooner.
If progress arrests – no descent with maternal effort – help to flex the head is indicated, especially if baby’s tone and colour are not ideal.
Want to learn more?
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)
Reitter A, Halliday A and Walker 2 (2020) Practical insight into upright breech birth from birth videos: a structured analysis. Birth. doi.org/10.1111/birt.12480