The Second Stage, a second time

By Dr. Eva Martin of Elm Tree Medical Inc.

Earlier this month, I wrote a blog post about the length of the second stage of labor- the time from reaching 10cm (fully) dilated to birth. The April 5 blog post discussed an awesome randomized clinical trial where the researchers assigned half the women to keep pushing and the other half to have an "expedited" delivery (c-section or vacuum or forceps). In the April 2016 Green Journal, a new observational study gives us ever more insight into this important and controversial topic.

Why is it so important? In a word: safety. Managing labor is a constant balancing act- is it safer to allow things to progress as they are or to intervene in some way? Currently, the cesarean section rate across the world is increasing, but cesarean births are not always the safest way to deliver a baby. For the average woman, a vaginal delivery is much safer. The question is: how do we balance the two? In the case of the second stage of labor: When is it safer to recommend a cesarean delivery and when is it safer to keep pushing?

This new study is observational, so it doesn't tell us about causation. However, the researchers- a consortium of 25 of some of the best hospitals in the country- collected an amazing amount of excellent data. One of the strengths of this study was the authors' ability to measure the time of active pushing. Prior studies could measure the time from reaching 10cm to delivery, but sometimes there are delays in there. Some women choose to "labor down" or delay pushing for some amount of time after reaching 10cm. Sometimes the decision to proceed with cesarean section could come 30 minutes before the OR is open and the delivery actually happens. This study was able to focus in like a laser on the time women were actively pushing. If you are the one doing the pushing, that number is probably very important to you! Currently, the standard recommendations are for the "second stage" and not "active pushing time." The standards allow 2 hours of pushing for first time moms and 3 hours for veterans without an epidural and an extra hour with an epidural.

The study included detailed information on 53,285 women with no prior cesarean delivery who had a term pregnancy with one baby in the head-down position and who reached 10cm dilation. As you might expect, the longer a woman pushed, the higher her odds of cesarean delivery were. However, a long pushing time definitely did not mean the woman was destined for a cesarean section! For first time moms, 78% of women who kept pushing after four hours had a vaginal delivery. For experienced moms, 82% of women who kept pushing after two hours had a vaginal delivery.

There were some characteristics associated with having a longer active pushing time: older women, non-Hispanic white women, women with diabetes mellitus, and women with an epidural. The authors also recorded the time women delayed pushing (the time from 10cm dilation to starting to push.) First time moms seem to have delayed pushing anywhere from not-at-all to about 45 minutes. Veteran moms generally did not delay pushing, or only waited up to about 15-25 minutes.

Now for the answers you've been waiting for: safety. Let's start with the safety for mothers. Women who pushed longer were more likely to have a cesarean delivery or an operative vaginal delivery (vacuum or forceps). They were also more likely to have a post-partum hemorrhage (a lot of blood loss after delivery) and a severe vaginal tear. However, we have to remember that this is an observational study so it doesn't tell us about causation. For instance, perhaps women who pushed longer have bigger babies, so it's the big baby that leads to a bigger tears and not the extra pushing.

Now on to the little ones: were the outcomes for the babies different? The authors created a composite score of a variety of complications for neonates: needing a ventilator for breathing, severe infection, shoulder nerve injury, bone fractures, seizures, brain injury, or death. Longer pushing was associated with higher risk of a complication for the baby. However, the increased risks were all about 1% or less. In absolute terms, the risk increases were very small. Some of the complications that were significantly different when analyzed individually were shoulder nerve injury (brachial plexus palsy), skull or other fracture (not shoulder fracture), seizures, and brain injury from lack of oxygen (hypoxic-ischemic encephalopathy).

The biggest conclusion of this fantastic study is stated by the authors: "Indeed, this study demonstrates that there is not a single time at which obstetric outcomes suddenly become worse." For those who have the enormous privilege of supporting women through labor, this new data will enable to them to give better information to women who are trying to decide if they want to keep pushing or not.