Julia D. López

A prospective cohort study of fetal heart rate monitoring: deceleration area is predictive of fetal acidemia

BACKGROUND Intrapartum electronic fetal monitoring is the most commonly used tool in obstetrics in the United States; however, which electronic fetal monitoring patterns predict acidemia remains unclear. OBJECTIVE This study was designed to describe the frequency of patterns seen in labor using modern nomenclature, and to test the hypothesis that visually interpreted patterns are associated with acidemia and morbidities in term infants. We further identified patterns prior to delivery, alone or in combination, predictive of acidemia and neonatal morbidity. STUDY DESIGN This was a prospective cohort study of 8580 women from 2010 through 2015. Patients were all consecutive women laboring at ≥37 weeks’ gestation with a singleton cephalic fetus. Electronic fetal monitoring patterns during the 120 minutes prior to delivery were interpreted in 10‐minute epochs. Interpretation included the category system and individual electronic fetal monitoring patterns per the Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria as well as novel patterns. The primary outcome was fetal acidemia (umbilical artery pH ≤7.10); neonatal morbidities were also assessed. Final regression models for acidemia adjusted for nulliparity, pregestational diabetes, and advanced maternal age. Area under the receiver operating characteristic curves were used to assess the test characteristics of individual models for acidemia and neonatal morbidity. RESULTS Of 8580 women, 149 (1.7%) delivered acidemic infants. Composite neonatal morbidity was diagnosed in 757 (8.8%) neonates within the total cohort. Persistent category I, and 10‐minute period of category III, were significantly associated with normal pH and acidemia, respectively. Total deceleration area was most discriminative of acidemia (area under the receiver operating characteristic curves, 0.76; 95% confidence interval, 0.72–0.80), and deceleration area with any 10 minutes of tachycardia had the greatest discriminative ability for neonatal morbidity (area under the receiver operating characteristic curves, 0.77; 95% confidence interval, 0.75–0.79). Once the threshold of deceleration area is reached the number of cesareans needed‐to‐be performed to potentially prevent 1 case of acidemia and morbidity is 5 and 6, respectively. CONCLUSION Deceleration area is the most predictive electronic fetal monitoring pattern for acidemia, and combined with tachycardia for significant risk of morbidity, from the electronic fetal monitoring patterns studied. It is important to acknowledge that this study was performed in patients delivering ≥37 weeks, which may limit the generalizability to preterm populations. We also did not use computerized analysis of the electronic fetal monitoring patterns because human visual interpretation was the basis for the Eunice Kennedy Shriver National Institute of Child Health and Human Development categories, and importantly, it is how electronic fetal monitoring is used clinically.

Duration of the Third Stage of Labor and Risk of Postpartum Hemorrhage.

OBJECTIVE: To characterize the duration of the third stage of labor and the association with postpartum hemorrhage in a contemporary cohort. METHODS: We performed a secondary analysis of a cohort of 7,121 women who had a vaginal delivery at or beyond 37 weeks 0 days of gestation at a single tertiary care center from April 2010 to August 2014. Active management of the third stage of labor was routinely used during the study period. The mean, median, interquartile range, 90th percentile, 95th percentile, and 99th percentile of the third stage of labor duration were calculated. Odds ratios were calculated to estimate the association between increased duration of third stage of labor and incidence of postpartum hemorrhage. RESULTS: The mean duration of the third stage of labor among women who had a vaginal delivery was 5.46 (standard deviation 5.4) minutes and median duration was 4 minutes. The 90th, 95th, and 99th percentiles were defined by 9, 13, and 28 minutes, respectively. Women with a third stage above the 90th percentile (n=705) had an increased risk for postpartum hemorrhage compared with a third stage below the 90th percentile (13.2% compared with 8.3%; adjusted odds ratio [OR] 1.82, 95% confidence interval [CI] 1.43–2.31). When the 90th percentile was further subdivided into 5-minute increments, risk for postpartum hemorrhage significantly increased beginning at 20–24 minutes compared with shorter third-stage durations (15.9% compared with 8.5%; adjusted OR 2.38, 95% CI 1.18–4.79). However, blood transfusion was not associated with third-stage duration (1.0% compared with 0.84% for third-stage duration greater than 90th compared with 90th percentile or less, adjusted OR 1.18, 95% CI 0.53–2.60). CONCLUSION: Our data show that postpartum hemorrhage risk increases significantly when the third stage of labor duration is 20 minutes or more, suggesting that the definition of a prolonged third stage of labor being 30 minutes or more may be outdated.

New Labor Management Guidelines and Changes in Cesarean Delivery Patterns

Background In 2010 the Consortium on Safe Labor published labor curves. It was proposed that the rate of cesarean delivery could be lowered by avoiding the diagnosis of arrest of dilation before 6 cm. However, there is little information on the uptake of the guidelines and on changes in cesarean delivery rates that may have occurred. Objective The objective of the study was to test the following hypotheses: (1) among patients laboring at term, rates of arrest of dilation disorders have decreased, leading to a decrease in the rate of cesarean delivery; (2) in the second stage, pushing duration prior to diagnosis of arrest of descent has increased, also leading to a reduction in the rate of cesarean delivery for this indication. As a secondary aim, we investigated changes in maternal and neonatal morbidity. Study Design This was a secondary analysis of a prospective cohort study of all patients presenting at ≥37 weeks’ gestation from 2010 through 2014 with a nonanomalous vertex singleton and no prior history of cesarean delivery. Rates of cesarean delivery, arrest of dilation, and changes in rates of maternal and neonatal morbidity were calculated in crude and adjusted models. Cervical dilation at diagnosis of the arrest of dilation, time spent at the maximal dilation prior to diagnosis of arrest of dilation, and time in the second stage prior to the diagnosis of arrest of descent were compared over the study period. Results There were 7845 eligible patients. The cesarean delivery rate in 2010 was 15.8% and, in 2014, 17.7% (P trend = .51). In patients undergoing cesarean delivery for the arrest of dilation, the median cervical dilation at the time of cesarean delivery was at 5.5 cm in 2010 and 6.0 cm in 2014 (P trend = .94). In these patients, there was an increase in the time spent at last dilation: 3.8 hours in 2010 to 5.2 hours in 2014 (P trend = .02). There was no change in the frequency of patients diagnosed with the arrest of dilation at <6 cm: 51.4% in 2010 and 48.6% in 2014 (P trend = .56). However, in these patients, the median time spent at the last cervical dilation was 4.0 hours in 2010 and 6.7 hours in 2014 (P trend = .046). There were 206 cesarean deliveries for the arrest of descent. The median pushing time in these patients increased in multiparous patients from 1.1 hours in 2010 to 3.4 hours in 2014 (P trend = .009); in nulliparous patients these times were 2.7 hours in 2010 and 3.8 hours in 2014 (P trend = .09). There was a significant trend toward increasing adverse neonatal and maternal outcomes (P < .001 for each). The adjusted odds ratio for adverse maternal outcome for 2014 compared with 2010 was 1.66 (95% confidence interval, 1.27–2.17); however, considering only transfusion, hemorrhage, or infection, there was no difference (P trend = .96). The adjusted odds ratio of adverse neonatal outcome in 2014 compared with 2010 was 1.80 (95% confidence interval, 1.36–2.36). Conclusion Despite significant changes in labor management that have occurred over the initial years since publication of the new labor curves and associated guidelines, the primary cesarean delivery rate was not reduced and there has been an increase in maternal and neonatal morbidity in our institution. A randomized controlled trial is needed.

Association of Fetal Heart Rate Baseline Change and Neonatal Outcomes

Objective The objective of this study was to describe the incidence of baseline change within normal range during labor and its prediction of neonatal outcomes. Materials and Methods This was a prospective cohort of singleton, nonanomalous, term neonates with continuous electronic fetal monitoring and normal baseline fetal heart rate throughout the last 2 hours of labor. We determined baseline in 10‐minute segments using Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria. We evaluated baseline changes of ≥ 20 and ≥ 30 bpm for association with acidemia (umbilical cord arterial pH ≤ 7.10) and neonatal intensive care unit (NICU) admission. Finally, we performed a sensitivity analysis of normal neonates, excluding those with acidemia, NICU admission, or 5‐minute Apgar < 4. Results Among all neonates (n = 3,021), 1,267 (41.9%) had change ≥ 20 bpm; 272 (9.0%) had ≥ 30 bpm. Among normal neonates (n = 2,939), 1,221 (41.5%) had change ≥20 bpm. Acidemia was not associated with baseline change of any direction or magnitude. NICU admission was associated with decrease ≥ 20 bpm (adjusted odds ratio [aOR]: 2.93; 95% confidence interval [CI]: 1.19 ‐ 7.21) or any direction ≥ 20 bpm (aOR: 4.06; 95% CI: 1.46‐11.29). For decrease ≥ 20 bpm, sensitivity and specificity were 40.0 and 81.7%; for any direction ≥ 20 bpm, 75.0 and 58.3%. Conclusion Changes of normal baseline are common in term labor and poorly predict morbidity, regardless of direction or magnitude.

A Prediction Model for Severe Maternal Morbidity in Laboring Patients at Term

Objective To determine the factors associated with severe maternal morbidity in a modern cohort of women laboring at term and to create a prediction model. Study Design This is a retrospective cohort study of all term, laboring patients with live births at a single tertiary care center from 2004 to 2014. The primary outcome was composite maternal morbidity including organ failure, amniotic fluid embolism, anesthesia complications, sepsis, shock, thrombotic events, transfusion, or hysterectomy. Multivariable logistic regression was used to identify independent risk factors. Antepartum, intrapartum, and combined risk scores were created and test characteristics were analyzed. Results Among 19,249 women delivering during the study period, 323 (1.68%) patients experienced severe morbidity, with blood transfusion the most common complication (286, 1.49%). Factors in the antepartum model included advanced maternal age, race, hypertension, nulliparity, history of cesarean delivery, smoking, and unfavorable Bishop score. Intrapartum factors included mode of delivery, use of cervical ripening agents or oxytocin, prolonged second stage, and macrosomia. The combined model had an area under the curve of 0.76 (95% confidence interval [CI], 0.73, 0.79). Conclusion This three‐part risk scoring system can help clinicians counsel patients and guide clinical decision making for anticipating severe maternal morbidity and necessary resources.

Risk of Neonatal Neurologic Morbidity in Advancing Term Gestations

Objective Placental insufficiency is associated with neonatal neurologic morbidity and late‐term gestations (410/7 ‐416/7 weeks). Whether late‐term infants are at increased risk of neurologic morbidity compared with term infants (390/7 ‐406/7 weeks) remains unclear. We aim to compare risk of neurologic morbidity among late‐term and term infants. Study Design This secondary analysis of a single‐institution prospective cohort study included all liveborn, nonanomalous singleton term and late‐term infants, with data on adverse neonatal outcomes up until 28 days of life. The primary outcome was a neonatal neurologic morbidity composite, defined by having one of these conditions: neonatal seizures, intraventricular hemorrhage, hypoxic‐ischemic encephalopathy, and neonatal hypothermic therapy. Secondary outcomes were the composites individual components and nonneurologic neonatal morbidity. Multivariable logistic regression adjusted for delivery mode, nulliparity, and labor type. Results Of 5,529 infants included, 747 were late term and 4,782 were term. The risk of composite neurologic morbidity was not significantly different among late‐term or term infants (0.5 vs. 0.6%; adjusted odds ratio: 0.59, 95% confidence interval: 0.21‐1.71). Overall neonatal morbidity was not significantly different in the two groups, though late‐term infants had a nonsignificantly higher prevalence of respiratory distress syndrome (5.5 vs. 3.3%) and meconium aspiration syndrome (0.7 vs. 0.2%). Conclusion Neonatal neurologic morbidity is uncommon after 39 weeks. Risk does not increase after 41 weeks.

Utility of the Simplified Bishop Score in Spontaneous Labor

Objective The objective of this study was to evaluate the relationship between the simplified Bishop score (SBS) on admission for labor and subsequent labor outcomes to identify women at higher risk for cesareans. Study Design This was a secondary analysis of a prospective cohort study of 4,733 singleton pregnancies. Adjusted odds ratios (aOR) were calculated comparing outcomes in women with an unfavorable SBS ≤ 5 to women with a favorable SBS > 5. A favorable SBS was compared with the individual parameters of dilation, effacement, and station. The primary outcome was vaginal delivery. Secondary outcomes were prolonged first stage, completion of first stage, oxytocin augmentation, and prolonged second stage. Results 47.8% of the patients admitted in labor had an unfavorable SBS. Nulliparous and multiparous patients with a favorable SBS were more likely to have a vaginal delivery (aOR 1.96, 95% confidence intervals [CI] 1.49-2.57; aOR 1.91, 95% CI 1.44-2.53) and less likely to require oxytocin augmentation (aOR 0.34, 95% CI 0.28-0.42; aOR 0.26, 95% CI 0.22-0.30. Compared with dilation alone, the SBS in its entirety was associated with a higher likelihood of vaginal delivery in nulliparous. Conclusion An unfavorable SBS on admission for labor is associated with a decreased likelihood of having a vaginal delivery.

Neurologic Injury in Acidemic Term Infants

Objective To determine whether arterial umbilical cord gas (aUCG) pH, in anatomically normal‐term infants, could select infants at risk for brain injury identified on magnetic resonance imaging (MRI). Study Design We performed a nested case‐control within a prospective cohort of 8,580 women. Cases, with an aUCG pH < 7.10, were temporally, age, and sex matched to controls with an aUCG pH ≥ 7.20. Bi‐ and multivariable analyses compared the presence and severity of brain injury. Secondary analyses estimated whether elevated arterial base excess or lactate were associated with brain injury. Results Fifty‐five cases were matched to 165 controls. There was no statistical difference in brain injury between the groups (adjusted odds ratio [aOR]: 1.8, 95% confidence interval [CI]: 0.7‐4.4]). Base excess ≥ ‐8 mEq/L was not significantly associated with brain injury (p = 0.12). There was no increase in risk of injury based on elevation of arterial lactate ≥ 4 mmol/L (p = 1.00). Cases were significantly more likely to have an abnormal score in several domains of the Dubowitz neurologic examination. Conclusion The aUCG acid‐base parameters alone are not sufficient clinical markers to identify term infants that might benefit from MRI of the brain to identify injury.

Umbilical Artery Lactate Correlates with Brain Lactate in Term Infants.

Objective The objective of this study was to determine the correlation between umbilical artery lactate with brain lactate in nonanomalous term infants. Study Design We performed a nested case‐control study within an on‐going prospective cohort of more than 8,000 consecutive singleton term (≥ 37 weeks) nonanomalous infants. Neonates underwent cerebral magnetic resonance imaging (MRI) within the first 72 hours of life. Cases (umbilical artery pH ≤ 7.10) were gender and race matched 1:3 to controls (umbilical artery pH > 7.20). Single voxel magnetic resonance spectroscopy (MRS), lactate, and N‐acetyl aspartate (NAA) for normalization were calculated using Siemens software (Plano, TX). Linear regression estimated the association between incremental change in umbilical artery lactate and brain lactate, both directly and as a ratio with NAA. Results Of 175 infants who underwent MRI with spectral sequencing, 52 infants had detectable brain lactate. The 52 infants with brain lactate peaks had umbilical artery lactate values of 1.6 to 11.4 mmol/L. For every 1.0 mmol/L increase in umbilical artery lactate, there was an increase in brain lactate of 0.02, which remained significant even when corrected for NAA. Conclusion MRS measured brain lactate is significantly correlated with umbilical artery lactate in nonanomalous term infants, which may help explain the observed association between umbilical artery lactate and neurologic morbidity.