Engagement is when the widest part of the baby’s presenting part (usually the head) enters the pelvic brim or inlet. A first baby usually engages two weeks before the due date, at 38 weeks gestation.
Baby has to get into the pelvis in order to go through the pelvis. Here’s more about why a baby may not engage, what’s normal and what’s concerning, and what to do about it.
Why does baby engage?
By 38 weeks, baby’s head needs to lower into the pelvic brim deeply enough so that the parietal eminence is below the level of the pelvic inlet. As the broad ligament, wrapping the uterus, softens at the end of pregnancy, the baby lowers in the abdomen. This softening encourages flexion. When tucked, baby’s head more easily lowers into the pelvic brim. Engagement happens when 4/5ths of the baby’s head is in the pelvis. The head is no longer ballotable; it can no longer be wiggled between the midwife or doctor’s fingers.
A first-time mother has a pear-shaped uterus, compared to an apple-shaped uterus of the experienced birther (Sutton). An experienced mother’s baby may not need to engage. If baby isn’t posterior and earlier labors have gone well, don’t worry about it. Labor will engage baby.
A mother who had to have her first baby by cesarean because baby remained high will be more likely to have a natural birth if her subsequent babies engage.
A breech baby may engage when the uterus allows the hips of the baby to lower beneath the level of the pelvic brim.
Why wouldn’t a baby engage?
Many of the occiput posterior babies don’t engage before labor starts. Of course, some do as well. When the baby hasn’t engaged and the due date has come and gone, I’ve almost always found the baby to be in the posterior position. Helping this baby to tuck their chin may help them engage.
Some babies have to rotate so the back of their head is on the mother’s left before they can engage in pregnancy or in labor. Another reason is pelvic shape in relation to fetal position. Many women have a gynecoid pelvis, wider side to side than front to back. When baby is flexed and baby’s back is on the left, the baby aims his or her crown into the brim. Few women have such a narrow front-to-back diameter (distance) from their pubic bone to their sacrum in the back of the pelvic inlet that baby must be on the left side to engage. Some women have a long front-to-back diameter with their anthropoid pelvis and then the direct posterior or direct anterior baby can engage.
Rarely, it might be due to a pelvis having too small an inlet to let the baby enter. This would be a case of CephaloPelvic Disporportion (CPD), or baby’s too big. Rickets, injury or an actually too-big-baby may be the cause here. CPD is rare, but does exist.
Personally, I don’t suspect CPD in pregnancy if baby isn’t engaged until baby is LOA or LOT, or the woman has bodywork specific to aligning her pelvis and releasing her sacrum. Some women will need to release a tight psoas to let baby descend into the pelvis.
Many babies don’t engage if they aren’t 38 weeks gestation in a first-time mother. This is normal. Check the dates.
It is not uncommon that a second, third or more baby to remain high and unengaged because the mother’s uterus is now apple shaped instead of pear shaped. This is not usually a problem. We would decide to intervene if the first labor was difficult and this baby was posterior.
A woman whose sacrum is sharply angled may have hours of labor before her baby engages. This woman will have a “sacral bustle” or a “ledge” on the top of her bum. To describe this, I say she could set a glass of water on this ledge, which isn’t really true, but gives the picture. Standing and leaning forward with contractions, in early to active labor is usually what these women do naturally and usually helps engagement. If not, a birthing stool or the abdominal lift and tuck usually brings the baby into the pelvis. From there, the labor usually proceeds rather quickly, as the mother’s hormones are well primed by the long, strong early labor.
What happens if the baby doesn’t engage before labor?
This depends on the reason and how easily it is to help baby engage.
Labor may also start before baby engages. When labor does start, contractions can be strong without much dilation and the baby remains high in the pelvis. Before the cervix opens well, we need to help baby come down into the pelvis well.
Some women are recommended to have an induction, even if their baby is not engaged. Get ready for an induction by increasing balance of the maternal structures, by helping baby get chin flexion, if needed, and out of the posterior position, if possible, with balancing activities. See more below.
Techniques to help a baby engage
Techniques to help baby engage will help open the brim, tuck the chin and rotate the baby to a left-sided presentation:
- Align the pelvic brim
- Align the sacrum which may be torqued on a vertical axis and distorting the lower uterine segment
- Relax the spasm out of the cervical ligaments (aka uterosacral or posterior ligaments, woman may have a history of retroverted cervix)
- Relax the psoas muscle pair (resolve chronic muscle tension in the illiopsoas)
- Help baby tuck the chin (flex the head)
- Helping a baby rotate to left occiput transverse (lateral), left occiput anterior, or occiput anterior
These engaging activities can be done before labor or during labor with bodywork.
Could there be another reason for babies not to engage?
It would be quite rare to have a placenta blocking baby’s way and preventing engagement. The soft tissue issues of a twist in the lower uterine segment from the above list is more common. A tight psoas can be another cause. Sometimes a mother or a mother and her provider can do what is needed to help baby engage before or during labor. Sometimes a bodyworker is best for a particular situation.
If a baby doesn’t engage, should we assume baby is posterior?
Beginning with balancing techniques will not cause an anterior baby to turn posterior. I would work on balancing the muscles, ligaments, pelvic joints, and resolving tight psoas issues.
Listen to the actual signs and symptoms in pregnancy of fetal position. A woman often feels little fingers wiggling between her pubic bone and her navel on both sides of her linea nigra when baby is posterior.
If baby hasn’t engaged in a first time mother by 38 weeks we might check more carefully for either occiput posterior presentation or to be sure dating of the pregnancy is correct.
Can she walk briskly with free-swinging thighs? Sit on a birth ball and make circles? There are several things to do both by getting bodywork (a chiropractor can help align her pelvis) and by her own activities.
I’m working with a woman who is about to be induced and her baby is at -2 station, should I suggest Walcher’s?
Balance in this case means activities to help the mother’s anatomy be more symmetrical on both sides as concerns tension and relaxation (or tone) of the muscles, ligaments, and alignment of the pelvic bones. These exercises can be begun now.
Once she has regular contractions, whether spontaneously or by induction, the Abdominal Lift and Tuck through 10 contractions may do the trick of lowering the baby into the pelvis, and if not, Walcher’s through 3 contractions (and between because its so uncomfortable she won’t likely go back to it a second time). Walcher’s in the air (as opposed to the deep birthing tub version) is for when other ways of getting baby to engage don’t work.
For a woman in labor, check out information and techniques to help the baby engage.
Babies naturally engage in the pelvis when the broad ligament is soft enough and the brim open enough. Fetal chin tucking and coming down from the mother’s left side helps more babies fit more mother’s inlets.
Generally, we hope for flexion and rotation before engagement. This is most important when we find baby in the posterior position and high after 38 weeks.
Work on Balance before working on rotation and descent. Sometimes we have a time issue, as when a woman’s membranes have released and when her provider has a time limit for her labor. Descent from a non-optimal position may have additional challenges that may be met with maternal positioning and activities in labor.
Fetal engagement may help the onset of labor be more spontaneous.