Edited/Updated: September 2015
Asynclitism is when the baby’s head is moving through the pelvis ‘tipped’ to one side. This is usually diagnosed by a vaginal examination in labour. However, asynclitism is rarely caused by the baby having his/her head tilted to one side and rarely a real problem. Instead, like the anterior lip, it is a normal part of the physiological process of birth.
Disclaimer: Routine vaginal examination has NO place during a physiological birth. Unfortunately vaginal examinations continue to be commonly used to determine progress despite the lack of evidence supporting this invasive intervention. In addition, most women do not experience a physiological birth and instead have their labour induced or augmented. Once an intervention is implemented it’s effects need to be monitored ie. assessment of cervical dilation. Therefore, the following explains what is felt during an examination in relation to what is happening as the baby descends and rotates through the pelvis.
Asynclitism: normal birth physiology
The baby enters the pelvis through the brim/inlet. The easiest way to do this is with the head in the transverse position (facing sideways to mother). However, the baby is not lying in a perfecting vertical position. The woman’s pelvis is tilted and her uterus/baby are also sticking out at an angle – check out a pregnant woman for confirmation. If at this point in the birth process you put your fingers into her vagina, you will feel the side of the baby’s head near the symphysis pubis. If you dig further you will feel the saggital suture towards the back of the pelvis. The baby’s head is not tilted… it is perfectly aligned with the baby and the pelvis.
Once the baby has descended into the cavity/mid-pelvis he will use the space and the counter pressure of the pelvic floor (unless the muscle tone is reduced by an epidural) to rotate an anterior position (facing towards mother’s back) to fit the shape of the pelvic outlet. It is not until the baby has made this rotation that you will feel the centre of the head in the middle of the pelvis. If the baby’s head is well flexed, you will also be able to feel the occiput, the posterior fontanelle and the lambdoidal suture (I love that word – lambdoidal).
As usual the text book depictions of a perfectly central saggital suture reflect our cultural need to keep birth neat and orderly. It fits in with the clean and clinical depictions of birth in which the woman is replaced by diagrams and graphs. The reality of a vaginal examination is very different and involves bodily fluids, squishy bits, hair, caput (swelling on baby’s head), moulding, the amniotic sac, difficult to distinguish parts of the head… and is usually an unpleasant experience for the woman (yes, she is involved). When birth becomes complicated there may be an indication for a vaginal examination (eg. to determine position), but in the absence of a complication there is no point. Telling a woman that her baby is asynclitic is at best pointless and at worst stress inducing… OK I’ll shut up about VE’s and save it for dedicated post later on. Moving on…
Asynclitism: a variation or complication
Occasionally the baby enters the pelvis with his/her head tilted down towards their shoulder (a variation). If the baby continues to descend in this position it can alter the progress of the birth process. The woman may experience irregular contractions without change over many hours. Most of the time the baby will sort themselves out, particularly with an actively mobile mother. Techniques to create more space in the pelvis may help to provide additional room for head wriggling and repositioning. I have found that techniques which help the baby move back out of the pelvis are very effective (eg. mother on all fours, bottom in the air + rebozzo work). Once baby is up and out a little, he can reposition and come down again with his head better aligned. Unfortunately a common response to this situation is to start IV syntocinon (pitocin) and create stronger contractions. It doesn’t take a genius to work out what happens if you have stronger contractions pushing the baby through the pelvis even harder and faster. The baby needs space to realign his head rather than more pressure and compaction (and the additional risk of syntocinon). Very occasionally the baby is unable to adjust his position and the birth becomes complicated – the baby becomes increasing compacted in the pelvis and begins to show signs of distress. In this situation the woman may require assistance to birth (instrumental birth or c-section).
Asynclitism is a normal part of the birth process. When it is caused by a tipped head it can alter the pattern of labour and may require additional work and support. It can be difficult to work out which type of asynclitism is happening via a vaginal examination (normal or a tilted head). Therefore it is best to keep fingers out of the vagina and focus on the woman and what she does or does not need from you.
I would love to hear your experiences of asynclitism.