If your cervix is not dilating, or your baby is not descending, as quickly as expected during the first stage, your doctor will try to assess why this is and if something can be done. Usually, your doctor will assess the three P's: the passenger (the size of the baby and his position in the uterus); the powers (the efficiency of your contractions); and the passage (the size and shape of your pelvis). These three elements work together and each one is important for your labor to progress smoothly.
There are several reasons why a labor may not progress. These include if the baby's head is too large for the mother's pelvis, known as cephalopelvic disproportion (CPD); if contractions are inefficient; and if the baby is in a posterior position with his back facing the mother's back.
Sometimes CPD may be suspected before labor, in late pregnancy. This may be the case if the doctor thinks that you have a narrow pelvis or a prominent sacral bone, both of which may make birth slower or more difficult. However, an assessment of the pelvis alone is not an accurate way to predict if you'll be able to have a successful vaginal birth and, even if the pelvis is not an optimal shape, the doctor may be happy for you to continue trying for a vaginal birth. This is because it's not the shape of your pelvis alone that is important, but the interaction between your baby (the passenger) and your pelvis.
If CPD is suspected, but the baby's head has engaged, a vaginal birth can still be attempted. The labor will be monitored with a labor graph and if there are signs that the baby is in distress, an emergency cesarean may be performed. If the head hasn't engaged toward the end of labor, a planned cesarean may be offered.
If your doctor suspects CPD in labor, she will reassess the baby's size to check if she originally underestimated his or her weight. Even though the combination of a large estimated weight and a slow labor can suggest that there may be delivery problems, often labor proceeds normally.
If your labor isn't progressing because your cervix is dilating slowly or has stopped dilating, your doctor will assess the frequency of your contractions, which should be every 2 to 3 minutes. She'll also assess how strong the contractions are by palpating your abdomen: the firmer it feels during contractions, the more likely they are to be effective. If contractions are more widely spaced than they should be and their strength indicates they're unlikely to be effective, she may use one or two techniques to speed up labor, known as augmenting labor. First, she may artificially rupture the membranes if they haven't already ruptured, a process known as ARM (see Breaking the water). This can shorten the duration of labor by around one to two hours.
If ARM has no effect, you may be given the drug oxytocin to increase the strength and frequency of contractions (see Breaking the water). Initially, a small dose is given and then increased over time until you're having three or four moderately strong contractions every 10 minutes. If this is done, you'll have continuous electronic fetal monitoring (see Oxytocin, Syntocinon, Pitocin) to check that the baby is not distressed by the sudden onset of stronger contractions.
If your labor is still not progressing several hours after the drugs have been started, then a cesarean may be recommended.
The best position for your baby in labor is an occipito-anterior position with the back of the head (occiput) facing your front. If the back of the head faces your back (occipito-posterior) this can make it hard for the baby to turn and move down the birth canal and can prolong labor. The doctor may suggest that you change positions to encourage the baby to turn. If the baby fails to rotate, forceps or vacuum may be needed to aid the delivery (see Forceps).
A gynecoid pelvis is the name given to a pelvis that has a circular shape. The generous proportions of this more typical "female-shaped" pelvis provides room for the head to pass through during the birth.
An android pelvis is the term used to describe a pelvis that has a more triangular shape. This reduces the room available for the baby's head to pass through and is more likely to cause problems during vaginal delivery.