Big Babies and Labor

Very often people talk about how the body doesn't build a baby that it can't birth. And that is mostly true, without a disease process (i.e. gestational diabetes), the body knows what size baby to make. But a baby one can birth is different than a baby one can easily birth. This is not intended to create stigma around big babies are discourage them from being born vaginally, On the contrary, this is meant to discuss the unique challenges of larger babies and the patience required for their vaginal delivery.

This is based on a small sample size of labors, observed both in home and in hospital. But every time I have tested this theory, it holds up. I'm always open to amending as new information is presented and happy to hear from other people's experience.

To define what big means is difficult - it is relative. Big for a tight pelvis can be 7 pounds, while a really roomy pelvis might easily accommodate a 9-pound baby with a normal labor pattern. There is a term Cephalo-Pelvic Disproportion (CPD), where a baby is assumed to be too big for the pelvis to accommodate, I would argue that more often, it is failure to accommodate the labor required for that baby to be birthed.

When a baby is large, very often the labor pattern is abnormal early on. The contractions will often start close together and intense, similar to OP. In some ways the cause is similar - in OP it is the wide diameter of the head, with large babies, the head diameter is large, even in an OA position. It takes much longer for this baby to engage. There will be strong contractions that are very intense, baby will be high for a long time, and often there will be little cervical progress. There also is likely to be an early urge to push. What is happening here?

To the best of my observations and understanding, the body is contracting hard to try to engage the baby, and because of the large head relative to the pelvis, it takes a lot of work to get the head into the pelvis. Meanwhile, the head is completely filling the pelvic brim, causing the sac to bulge, the sac then puts pressure on the cervix with contractions causing an early urge to push (not immediately, but earlier in labor than anticipated), and likely also feeding the positive feedback loop of contractions (the Ferguson Reflex) causing harder, stronger contractions. These contractions feel very intense, not only because of their intensity, but the amount of spreading the pelvic bones must do to accommodate the baby.

There may be some early decelerations in the baby's heart rate. This is because the head is actually molding to the pelvic bones to fit through. Those will resolve once the baby gets through the bones. They are akin to the decelerations seen when the head hits the cervix.

In my experience with these labors an epidural is a major detriment. Because the labor is longer and more intense than standard labors, it is more difficult for a person to opt to forego pain medication. The problem is, these labors require a lot of movement and effort. Very often the laboring body instinctively knows how to move to help itself, and when it doesn't, hopefully there is a doula, midwife, or nurse in the room with the skills to help the baby's descent. Though I have not yet seen a labor like this lead to a successful vaginal birth with an epidural, I have seen a number of them be successful at home.

In the births where there was an epidural that ultimately ended is cesarean, babies tended to be at a station of -2. This means they were barely engaged in the pelvis, yet when they were born, their heads had fairly extreme molding that clearly resembled the shape of a pelvis. You could see how the baby had begun to work its way through the bones, and how the baby was spreading the bones with its head.

There are many techniques to work through these labors depending on stage and presentation, but movement, patience, and really strong support teams seem to be the most important factors.