Is immediate or delayed pushing better in spontaneous vaginal delivery?

October 16, 2018
Judith M. Orvos, ELS
Judith M. Orvos, ELS

a BELS-certified medical writer and editor, and an editorial consultant for Contemporary OB/GYN

,
Ben Schwartz
Ben Schwartz

Ben Schwartz is Associate Editor, Contemporary OB/GYN.

A recent study looked at which approach to second-stage labor results in higher spontaneous vaginal delivery rates and lower rates of maternal and neonatal complications. PLUS: What makes hospitals safe for mothers and babies? ALSO: Does eating meat increase risk for breast cancer?

The two most common approaches to second-stage labor are to delay maternal pushing or initiate immediate pushing once complete cervical dilation occurs, but neither is considered to be the gold standard. A study published in JAMA examined whether immediate or delayed pushing results in higher spontaneous vaginal delivery rates and lower rates of maternal and neonatal complications.

The multicenter, randomized clinical trial included 2404 nulliparous pregnant women at or beyond 37 weeks’ gestation who were admitted for spontaneous or induced labor with neuraxial analgesia between May 2014 and December 2017. At complete cervical dilation (10 cm), patients were randomized to immediate pushing or delayed pushing. Women in the immediate pushing group (n=1200) were instructed to initiate pushing at randomization and those randomized to delay pushing were instructed to wait 60 minutes before pushing.        

The primary endpoint of the study was spontaneous vaginal delivery that occurred without the use of forceps, vacuum, or cesarean delivery. Secondary endpoints included total duration of labor, duration of active pushing, and rates of postpartum hemorrhage, operative vaginal delivery and cesarean, perineal lacerations, and neonatal morbidity.

Mean time from complete cervical dilation to pushing was 18.9 minutes (SD =  15.1 minutes) in the immediate pushing group and 59.8 minutes (SD = 21.8 minutes) in the delayed pushing group. Women in the immediate pushing group had a significantly shorter mean duration of second-stage labor (102.4 minutes) compared to women in the delayed pushing group (134.2 minutes). However, the immediate pushing group had a significantly longer mean duration of active pushing (83.7 minutes) compared to the mean duration of active minutes in the delayed pushing group (74.5 minutes). 

In the two groups, rates of operative vaginal and cesarean delivery were low and did not differ significantly. In the immediate pushing group, the rate of postpartum hemorrhage was much lower than in the delayed pushing group (2.3% vs 4.0%, respectively). Rates of chorioamnionitis during second-stage labor were also significantly lower in women in the immediate pushing group compared to the delayed pushing group (6.7% vs 9.1%, respectively). There was no significant difference between the two groups when comparing rates of endometriosis, neonatal morbidity, or perineal lacerations. 

The authors identified a number of strengths and limitations. Among the strengths mentioned was that the multicenter trial is regionally representative of obstetric patients in the United States. Because obstetrical management was at the discretion of the patient’s clinician, the researchers believe the results may be generalizable to broader populations. Limitations included lack of adjustment for multiple comparisons, raising the possibility that some significant differences in the secondary and exploratory outcomes could have occurred by chance. The study could not be blinded, which raised the possibility of bias. 

While the authors identified pros and cons of both delivery methods, ultimately for nulliparous women receiving neuraxial anesthesia, the timing of second-stage pushing did not affect the rate of spontaneous vaginal delivery. However, they also noted that observational data in this and previous studies have suggested that every additional hour spent during the second stage of labor after the first hour increases risk for maternal and neonatal morbidity and delayed pushing significantly increased the duration of the second stage. 

What makes hospitals safe for mothers and babies?

Hospitals with low rates of maternal death don’t necessarily have equally low rates of neonatal death, according to results of a new study from investigators from Yale and Stanford. The findings, the authors say, point to a need for more research to identify factors that contribute to hospital performance and contribute to increased rates of overall maternal and neonatal morbidity.

Published in Birth, the conclusions are from an analysis of hospital performance that accounted jointly for maternal and newborn morbidity rates and looked at variation in the combined maternal-newborn outcome across hospitals. Supported by the Agency for Healthcare Research and Quality, the study was based on data from birth certificate and hospital discharged records reflecting more than 1.3 million term births at 248 hospitals from 2010 to 2012. 

After adjusting for patient clinical risk factors, the authors calculated a risk-standardized rate of severe maternal morbidities and a risk-standardized rate of severe newborn morbidities for each hospital. Then they ranked the hospitals based on combined information on those rates. The composite measure, developed by the Centers for Disease Control and Prevention, took into consideration in-hospital maternal death, maternal transfer for acute inpatient care, and diagnosis of 16 major morbidities. For neonatal outcome, severe unexpected newborn morbidities were measured. 

Of the hospitals, 28.6% were urban teaching hospitals, 7.7% were in rural areas, and 65.7% were private nonprofit hospitals. Across these institutions, the authors found that risk-standardized severe maternal and severe newborn morbidity rates varied substantially (10thto 90thpercentile range = 67.5 to 148.2 and 141.8 to 508.0 per 10,000 term births, respectively) but there was no significant association between the two (P= 0.15). Government (non-federal) hospitals were more likely than other hospitals to be in worse rank quartiles (Pvalue for trend = 0.004) whereas large volume was associated with better rank among hospitals in the first three quartiles (P= 0.004). 

“Contrary to conventional beliefs,” the authors said, “we found no significant correlation between the two rates [maternal and severe newborn morbidity], suggesting that hospitals which excel in maternal outcomes may not perform well in newborn outcomes.” They theorize that there may be a number of reasons for the lack of concordance: disproportionate focus on one side of the outcomes by a hospital, differing perceptions about quality of care on the part of obstetric and pediatric providers, and differences in level of capacity of care between obstetric and pediatric services at an institution.    

The findings, the researchers said, point to a need to consider maternal and newborn outcomes jointly to fully understand how a hospital performs with perinatal care. For mothers, the most prevalent morbidities that differed progressively across hospital rank quartiles were severe hemorrhage, disseminated intravascular coagulation, and heart failure during procedure/surgery. For neonates, they were severe infection, respiratory complication, and shock/resuscitation. These are the complications, the authors said, that may warrant particular attention in future research.

Does eating meat increase risk for breast cancer?

Consumption of red and processed meat has been linked with colorectal, pancreatic and prostate cancer, but its association with breast cancer has been unclear due to conflicting findings from previous studies. A recent meta-analysis, published in the International Journal of Cancer, takes a closer look at the evidence regarding red meat and breast cancer. 

For the analysis, the authors identified 466 relevant citations published up until January, 2018. Red meat was defined as unprocessed muscle meat including beef, veal, pork, lamb, mutton, horse, or goat meat. Processed meat refers to meat that has been transformed through salting, curing, fermentation, smoking or other processes to enhance flavor or improve preservation. 

After screening, the authors whittled the studies down to 20 published articles on red meat, processed meat, or total red meat (red meat and processed meat) and breast cancer incidence. They included cohort studies, nested case-control studies, and clinical trials. Eight studies were from North America, nine studies were from North America, and one study was from Japan. For all but two studies, which used dietary records, diet was assessed through a food frequency questionnaire. The amount of meat consumed was recorded as gram/day or week, serving/day, or gram/1000 kcal. 

The authors conducted three separate analyses for red meat, processed meat and total red meat. A total of 1,1 million women and 33,493 cases of breast cancer (13 studies), were included in the red meat and overall breast cancer meta-analysis. A total of 1.25 million women and 37,070 cases of breast cancer were included in 15 studies of processed meat as were more than a half million women and more than 21,000 cases of breast cancer in the seven studies of total red meat. 

Across 13 studies that examined the association between red meat and overall breast cancer, red meat consumption was associated with a nonsignificant increased risk of breast cancer. The random-effects summary of relative risks (RR) comparing the highest vs. the lowest category of red meat was 1.06 (95% CI: 0.99, 1.14) with moderate inconsistency across the studies. Among 15 studies that examined the association between processed meat and overall breast cancer risk, the risk estimate comparing the highest vs. the lowest category was 1.09 (95% CI: 1.03, 1.16). Among seven studies that examined the association between total red meat and overall breast cancer, the risk estimate comparing the highest vs the lowest category was 1.09 (95% CI: 0.99, 1.21).   

The authors also examined the association between red and processed meat and risk of premenopausal and postmenopausal breast cancer. Among six cohort studies examining red meat intake and premenopausal breast cancer, the risk estimate comparing the highest vs the lowest category was 1.07 (95% CI: 0.97, 1.18). Among nine studies that examined the association between red meat intake and postmenopausal breast cancer, the risk estimate comparing the highest vs the lowest category was 1.08 (95% CI: 0.99, 1.17). A higher intake of processed meat was not associated with an increased risk of premenopausal breast cancer, but it was associated with a higher risk of postmenopausal breast cancer (highest vs lowest category RR = 1.10, 95% CI: 1.03, 1.17).

The authors said their study had several strengths and limitations. Identified strengths include limiting their analysis to prospective cohort, nested case-control, and clinical trials. The included studies also had wide variations in study populations, but low to moderate heterogeneity across the studies themselves allowed the authors to feasibly pool the results from the different studies. The authors also had the ability to evaluate the association of red meat intake and breast cancer events in different populations with different diets. Identified limitations included publication bias, the possibility of residual confounding, and the fact that some of the included studies also included processed poultry in their definition of processed meat. However, the authors believe that their findings illustrate a significant risk of breast cancer with the intake of processed meat and physicians should counsel their patients about it and suggest diet changes as a preventative measure.