SAN DIEGO – The crossing times for the rate of spontaneous vaginal delivery versus a composite maternal or neonatal morbidity/mortality occurred slightly earlier than current recommended guidelines for women with an epidural (2.6 hours versus 3 hours), regardless of parity, results from a large federally funded retrospective study showed.
After this time, the risk of morbidity was higher than the chance of vaginal delivery.
But for women without an epidural, the crossing times for spontaneous vaginal delivery (SVD) and any morbidity occurred slightly later than current guidelines suggest (2.4 hours versus 2 hours in nulliparous women, and 2.3 hours versus 1 hour in multiparous women). Only in multiparous women without an epidural did the lines cross at least 1 hour later, Dr. Katherine Laughon Grantz said at the annual Pregnancy Meeting sponsored by the Society for Maternal-Fetal Medicine.
Dr. Katherine Grantz
“We provide data that can be used to balance chances of SVD versus morbidity with increasing duration of second stage,” said Dr. Grantz, an investigator at the National Institute of Child Health and Human Development.
A June 2000 clinical management guideline from the American College of Obstetricians and Gynecologists states that operative vaginal delivery is indicated for nulliparous women who lack progress after 3 hours with an epidural, or 2 hours without an epidural. For multiparous women, the guideline is 2 hours with an epidural and 1 hour without. Dr. Grantz said that historical guidance for the 2-hour rule was first described in the 1850s by expert opinion and case series.
“Recently, however, it’s been recommended that it is safe to extend the current ACOG guidelines by 1 hour,” she said.
In 2014, Dr. Grantz and her colleagues published a study showing that prolonged second stage is associated with increased risk of maternal and neonatal morbidity (Obstet. Gynecol. 2014;124:57-67).
“Therefore, our group wanted to take this a step further, to determine the second-stage duration wherein the chance of vaginal delivery became so low it was outweighed by the increased risk of morbidity,” she said.
The researchers used data from the Consortium on Safe Labor, a study of 19 hospitals within 12 medical institutions in the United States. Medical records from 228,438 deliveries between 2002 and 2008 were evaluated, including patient demographics, prenatal complications, labor and delivery information, and maternal and neonatal outcomes.
They limited the analysis to singleton gestations delivered greater than or equal to 36 weeks’ gestation and excluded nonvertex presentation, antepartum stillbirth prior to onset of labor, women with a prior uterine scar, congenital anomalies, and cervical exams prior to vaginal delivery that were less than 10 cm or missing. This resulted in a total of 103,415 deliveries studied.
The researchers analyzed the groups in four strata: by parity (nulliparous or multiparous), and by epidural status (yes or no). Four outcomes were studied: spontaneous vaginal delivery; a composite of maternal morbidity (which included postpartum hemorrhage, blood transfusion, cesarean hysterectomy, endometritis, or ICU admission); composite neonatal morbidity/mortality (including shoulder dystocia, 5-minute Apgar score of less than 4, need for continuous positive airway pressure resuscitation or higher, NICU admission, sepsis, pneumonia, hypoxic-ischemic encephalopathy/periventricular leukomalacia, seizure, intracranial hemorrhage/periventricular hemorrhage, asphyxia, or neonatal death); and any maternal or neonatal morbidity.
They calculated the hazard rates of each outcome and created joint models for hazard rates that model rate of spontaneous vaginal delivery versus the risk of each of the three morbidity categories.
Dr. Grantz reported that for nulliparous women with an epidural, extending the second stage from 3 to 4 hours resulted in 16% of maternal and 15% of neonatal morbidities, with approximately 5.5% additional SVD during that hour.
“Our data are limited because these are retrospective data,” Dr. Grantz noted. “Women who were allowed to continue with a prolonged second stage might have been different than women who did not continue with a prolonged second stage. We also did not have information on delayed versus active pushing, and we lacked long-term maternal and child outcomes.”
But the major strength of the study is the large number of deliveries, she said, which allowed the researchers to investigate rare neonatal outcomes at term.
The study was supported by the NICHD. Dr. Grantz reported having no relevant financial conflicts.
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