Asynclitism means asymmetrical and is the term used when a baby’s head is tipped towards one shoulder.
Early in labor the baby’s head enters the brim of the pelvis in asynclitism –tipped- to get around the protruding base of the spine (sacral promontory).
When the nurse checks the cervix at 3 cm she’ll notice that the baby’s head is closer to the mother’s front (usually). There is space between the baby’s head and the mother’s sacrum in back.
Normally, the head has usually filled in the space evenly by 4-5 cm. The head has become symmetrical inside the pelvic canal. The head is synclitic.

Asynclitism only becomes a problem when it persists beyond early labor. The asynclitic head has a harder time passing through the narrow part of the pelvis; the ishial spines. Labor becomes longer, and this added length continues through 2nd stage.

Labor with an asynclitic baby

The baby enters the pelvic tunnel in the asynclitic position. Facing the right hip, the LOT baby usually enters with a posterior asynclitism. This is the good type of posterior! It means that the center of the baby's head, felt by the saggital suture between the parietal bones, is towards the front and the right parietal bone enters first. 

If the bag of water releases suddenly with a strong contraction there is a possibility that the baby's head comes down to the mid pelvis while still asynclitic. Asynclitism may be caused by a twist in the lower uterine segment causing the baby to twist to fit the area. More typically, the pelvic floor is asymmetrical and so the head gets tipped as it is pressed down with strong contractions on the uneven edges of the opening to the pelvic floor.

Labor is often longer. Dilation often takes longer and there can be a delay in progress at about 8-9 cm or 9 1/2 centimeters for many hours.

Contractions are often strong throughout, unlike the ebb and surge of a posterior labor. Though that can happen too.

A mother may have significant pain in one hip. Hip pain may also be from one of the baby's arms being up along the head or a spasm in the muscles within the broad ligament.

Longer second stages

It not unusual for second stage to last 3-6 hours when the head is tipped. I’ve attended first time mothers with second stages 2 and 3 times longer than this.

The baby can develop a caput. This doesn't mean that the baby won't fit, necessarily, but that maternal positioning to open the pelvis is necessary. Give plenty of time without pushing for molding to occur.  

What to do?

Do the Pelvic Floor Release.

Sometimes resting and not pushing at all through 2-5 contractions helps molding. Let the mom rest in a Rest Smart position. 

Eating small amounts and drinking warm honey tea helps keep labor contractions strong enough to keep moving the baby.

Lying down in one position is not likely to allow the baby to descend further downward. Very specific and persistent techniques are often necessary.
Vertical positions, such as standing and doing the lunge, Doing the Dangle should follow the Pelvic Floor Release.

Pulling on a towel or rebozo during pushing contractions and

Medically assisted birth

Sometimes the doctor will want to use a vacuum (ventouse) or forceps during a contraction to pull the head out. There are some risks, of course, but if the head is low enough, attempting to continue with a vaginal birth avoids the risks of major surgery.
Sometimes more time is needed, but also an attendant with the unique skills of supporting the long labor naturally. More than just postponing a cesarean, skills for natural labor includes knowing when enough is enough and when and how to help a mother continue labor without physical or emotional trauma.

Supporting the asynclitic labor

There is a dance the midwife does between forces of inertia and forces of birth. When to eat, when to rest and when to work the pelvis are vitally important when labor is long and the second stage even longer.

A doula, or two, can mean the difference between a vaginal birth and surgery. Her talents in emotional support may find themselves calming the nurses and providers.

The mother needs to want to continue the birth. After a particularly difficult birth we want to know that she is joyous and not second guessing herself. The birth team may need to get together to discuss the birth.

In labor, if the mother decides enough is enough, the support team must seriously consider their options for finishing the birth. With a birth team that works well together and a willing mother, many mothers will perservere to finish the birth themselves. They will feel proud and may a bit confused as to why their labor was so difficult. What we don’t want is to have the mother feel like she was suffering. Listen to the mother and let her lead. Give encouragement while leaving an opening for her to lay down her hand.

The story, The Long Labor That Wasn’t is about an asynclitic posterior birth. There is another story of an asynclitic posterior labor at the end of the article called Pelvic Floor Release. Both babies in these stories had their chins extended. Both babies were born at home in good health. Asynclitism might repeat in a future birth, but often it does not.