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Success rate for vaginal delivery high even after prolonged labor

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Benefits of vaginal birth should be weighed against slight risks of waiting

Friday, October 3, 2014

Listen to this podcast (MP3 - 5.5 MB).

Ms. Christine Guilfoy: Welcome to the National Institutes of Health. I'm Christine Guilfoy and this is Research Developments, a podcast of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the NICHD. Health care professionals generally prefer childbirth through the birth canal to cesarean delivery. Like any surgery, cesarean carries risks such as infection, bleeding, and reactions to the anesthetic. When the second stage of labor—the pushing phase—lasts more than 2 hours, health care professionals generally become concerned and start thinking about cesarean delivery.  But the research evidence for intervening after the 2-hour point is mixed. Some studies have shown increased risks, while others have not. NICHD Epidemiology Branch investigator Dr. Katherine Laughon and her colleagues examined medical records of deliveries at hospitals to determine if it's best for physicians to step in after the 2-hour mark or whether it's advisable to wait for delivery to take place naturally. They concluded that waiting was associated with a slight increase in risks for mothers and babies, and they advised that women and their health care practitioners weigh the increased benefits of vaginal delivery against the slightly increased risk. 

Dr. Laughon is with us today to explain her findings. Dr. Laughon, thank you for talking with us today.

Dr. S. Katherine Laughon: Thank you for having me.

Ms. Guilfoy: First, Dr. Laughon, could you tell us a little more about the second stage of labor?

Dr. Laughon: The second stage of labor is the time from when the cervix, or the opening to the uterus, is fully dilated and a woman starts pushing until delivery of the baby. And it 's important to know what a normal length of the second stage is, because clinicians need to balance allowing enough time to safely achieve vaginal delivery without significantly increasing the risks for the mother and the baby.

Ms. Guilfoy: How long does it usually take?

Dr. Laughon: Well, the amount of time that has traditionally been recommended depends on whether it 's the mother's first delivery or not—because it takes longer for first-time mothers—and also whether she has an epidural, because labor is slower with an epidural. So the American College of Obstetricians and Gynecologists recommends that first-time mothers are allowed 2 hours to push and an extra hour—or 3 hours—if they have an epidural. For mothers who have had a prior vaginal delivery, it's recommended 1 hour to push and an extra hour—or 2 hours—if they have an epidural. However, recently it has been suggested that women should be allowed at least an extra hour to push to increase the chance that women can have a vaginal delivery.

Ms. Guilfoy: OK. So actually it can be anywhere from 2 to 3 hours according to the guidelines? ​ ​

Dr. Laughon: Exactly. It depends on whether a mother has had a baby before and whether she has an epidural.

Ms. Guilfoy: OK. And why are there concerns about the second stage of labor lasting beyond the 2 or 3 hours as given in the guidelines?

Dr. Laughon: Prior studies have found that there were increased risks of morbidity for mothers who have what we call a prolonged second stage. And these primarily include postpartum hemorrhage or excessive bleeding after the delivery; maternal fevers; infections; and trauma or tears. However, the risk to the baby has been less clear, and this is in part because prior studies didn 't have enough numbers to study the more rare outcomes.

Ms. Guilfoy: And so you looked at medical records to find out what might happen when labor exceeds these recommended guidelines. How many records were involved?

Dr. Laughon: We used de-identified medical records from the  Consortium on Safe Labor study, which included 12 sites and 19 hospitals across the United States. And we were able to include 43,810 first-time mothers, of which 81% had an epidural, and 59,605 mothers with a prior vaginal delivery, of which 73% had an epidural.

Ms. Guilfoy: OK. And so, what did you find?

Dr. Laughon: We found that women can achieve high rates of vaginal delivery with a prolonged second stage. However, there were small increases in morbidity for both mothers and their babies.

So, for example, for first-time mothers, prolonged second stage was associated with a 1-day longer hospital stay and increased risk of an infection called chorioamnionitis, which is an infection of the gestational sac that surrounds the baby inside the uterus, as well as an increased risk of maternal tears. 

And first-time mothers with an epidural also had increased risks of endometritis, which is an infection of the uterus; wound separation; and postpartum hemorrhage. 

We also found that prolonged second stage was associated with increased risks for the baby as well. And it depended on the group, but babies born after a prolonged second stage in general were more likely to be admitted to the neonatal intensive care unit. And it's important to note that these were babies that were born at term, so there wasn't any chance of prematurity. 

So, for first-time mothers, babies had more sepsis, which is a blood infection; and a slight increased risk of asphyxia in first-time mothers with an epidural. And this is when—situations of when there's not enough oxygen to the baby. We also observed an increased risk of perinatal mortality in women without an epidural. 

It was reassuring that mothers who had an epidural did not have an increased risk of perinatal death or neonates with what's called hypoxic ischemic encephalopathy, which is brain injury that occurs in situations of decreased oxygen.

Ms. Guilfoy: Why is there a little more risk when labor is prolonged? Do we know exactly how that might lead to a complication like those you found?

Dr. Laughon: Our study didn 't explore these mechanisms. However, it is important to note that the increased risk cannot necessarily be attributed to the duration itself. And this is because the underlying reason for a longer duration may contribute to morbidity—for example, infection of the gestational sac, or if the baby is large and has an increased size; these are situations that are both associated with longer duration and also with increased morbidity for the mother and the baby. 

We did observe, as I previously mentioned, that there was an increased risk of operative vaginal delivery, and this is known to be associated with increased risks for the mother and the baby. We repeated the analysis in first-time mothers with an epidural who had a spontaneous vaginal delivery, however, and found similar results. So these findings indicate that longer duration itself may be an independent risk factor for maternal and neonatal morbidity.

Ms. Guilfoy: OK. And what 's the takeaway message for pregnant women and their doctors?

Dr. Laughon: As a practicing high-risk obstetrician, I know firsthand how upsetting it is for women who have been pushing and are so close yet are still undelivered once they reach the recommended time limits for the second stage of labor. Our study provides important information on the overall risks with continuing to attempt a vaginal delivery, to help guide clinical decision making.  

Ultimately, the benefits of increased vaginal delivery should be weighed against the potential small increases in maternal and neonatal risks with prolonged second stage.

Ms. Guilfoy: Great. And, well, thank you so much for talking with us, Dr. Laughon.

Dr. Laughon: Thank you.

About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit the Institute's website at http://www.nichd.nih.gov/.​​​​

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