Asynclitic birth

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In obstetrics, asynclitic birth, or asynclitism, refers to the malposition of the fetal head in the uterus relative to the birth canal.^[1] Many babies enter the pelvis in an asynclitic presentation, but in most cases, it corrects itself spontaneously during labor.^[2] Asynclitic presentation is not to be confused with a shoulder presentation, where the shoulder leads first.

Fetal head asynclitism may affect the progression of labor, increase the need for obstetrical intervention, and may be associated with difficult instrumental delivery.^[3] The prevalence of asynclitism at transperineal ultrasound was common in nulliparous women at the second stage of labor and seemed more commonly associated with non occiput anterior position, suggesting an autocorrection occurs in many cases.^[3]

When the self-correction does not occur, obstetrical intervention is necessary to deliver the child. Persistence of asynclitism can cause problems with dystocia, and has often been associated with cesarean births. However, with a skilled midwife or obstetrician a complication-free vaginal birth can sometimes, though not necessarily, be achieved through movement and positioning of the birthing person, and patience and extra time to allow for movement of the baby through the pelvis and moulding of the skull during the birthing process if this is safe in the circumstances. Other options include the use of vacuum-assisted delivery and forceps.^{[medical citation needed][4][unreliable source?]} There is no evidence to suggest that people with previous asynclitic presentation are more likely to experience it in subsequent childbirth.^{[5][better source needed]}