Preliminary evaluation of dynamic glucose enhanced MRI of the human placenta during glucose tolerance test

Background

To investigate dynamic glucose enhanced (DGE) chemical exchange saturation transfer (CEST) MRI as a means to non-invasively image glucose transport in the human placenta.

Methods

Continuous wave (CW) CEST MRI was performed at 3.0 Tesla. The glucose contrast enhancement (GCE) was calculated based on the magnetization transfer asymmetry (MTRasym), and the DGE was calculated with the positive side of Z-spectra in reference to the first time point. The glucose CEST (GlucoCEST) was optimized using a glucose solution phantom. Glucose solution perfused ex vivo placenta tissue was used to demonstrate GlucoCEST MRI effect. The vascular density of ex vivo placental tissue was evaluated with yellow dye after MRI scans. Finally, we preliminarily demonstrated GlucoCEST MRI in five pregnant subjects who received a glucose tolerance test. For human studies, the dynamic R2* change was captured with T2*-weighted echo planar imaging (EPI).

Results

The GCE effect peaks at a saturation B1 field of about 2 μT, and the GlucoCEST effect increases linearly with the glucose concentration between 4-20 mM. In ex vivo tissue, the GlucoCEST MRI was sensitive to the glucose perfusate and the placenta vascular density. Although the in vivo GCE baseline was sensitive to field inhomogeneity and motion artifacts, the temporal evolution of the GlucoCEST effect showed a consistent and positive response after oral glucose tolerance drink.

Conclusions

Despite the challenges of placental motion and field inhomogeneity, our study demonstrated the feasibility of DGE placenta MRI at 3.0 Tesla.

Placental MRI: Developing Accurate Quantitative Measures of Oxygenation

The Human Placenta Project has focused attention on the need for noninvasive magnetic resonance imaging (MRI)-based techniques to diagnose and monitor placental function throughout pregnancy. The hope is that the management of placenta-related pathologies would be improved if physicians had more direct, real-time measures of placental health to guide clinical decision making. As oxygen alters signal intensity on MRI and oxygen transport is a key function of the placenta, many of the MRI methods under development are focused on quantifying oxygen transport or oxygen content of the placenta. For example, measurements from blood oxygen level-dependent imaging of the placenta during maternal hyperoxia correspond to outcomes in twin pregnancies, suggesting that some aspects of placental oxygen transport can be monitored by MRI. Additional methods are being developed to accurately quantify baseline placental oxygenation by MRI relaxometry. However, direct validation of placental MRI methods is challenging and therefore animal studies and ex vivo studies of human placentas are needed. Here we provide an overview of the current state of the art of oxygen transport and quantification with MRI. We suggest that as these techniques are being developed, increased focus be placed on ensuring they are robust and reliable across individuals and standardized to enable predictive diagnostic models to be generated from the data. The field is still several years away from establishing the clinical benefit of monitoring placental function in real time with MRI, but the promise of individual personalized diagnosis and monitoring of placental disease in real time continues to motivate this effort.

A comorbidity-based screening tool to predict severe maternal morbidity at the time of delivery

BACKGROUND

The obstetric comorbidity index summarizes the burden of maternal comorbidities into a single number and holds promise as a maternal risk-assessment tool.

OBJECTIVE

The aim of this study was to assess the clinical performance of this comorbidity-based screening tool to accurately identify women on labor and delivery who are at risk of severe maternal morbidity on labor and delivery in real time.

STUDY DESIGN

All patients with pregnancies ≥23 weeks gestation presenting to labor and delivery at a single tertiary-care center from February through July 2018 were included in the study. The patient's primary labor and delivery nurse assessed patient comorbidities and calculated the patient's obstetric comorbidity index. The score was recalculated at each 12-hour shift change. A multidisciplinary panel of clinicians determined whether patients experienced severe maternal morbidity based on the American College of Obstetrics and Gynecology and Society for Maternal-Fetal Medicine consensus definition, blinded to the patient's obstetric comorbidity index score. We analyzed the association between the obstetric comorbidity index score and the occurrence of severe maternal morbidity.

RESULTS

The study included 2828 women, of whom 1.73% experience severe maternal morbidity (n=49). The obstetric comorbidity index ranged from 0-15 for women in the study cohort, with a median obstetric comorbidity index of 1 (interquartile range, 0-3). The median obstetric comorbidity index score for women who experienced the severe maternal morbidity was 5 (interquartile range, 3-7) compared with a median of 1 (interquartile range, 0-3) for those without severe maternal morbidity (P<.01). The frequency of severe maternal morbidity increased from 0.41% for those with a score of 0 to 18.75% for those with a score ≥9. For every 1-point increase in the score, patients experienced a 1.55 increase in odds of severe maternal morbidity (95% confidence interval, 1.42-1.70). The c-statistic for the obstetric comorbidity index score was 0.83 (95% confidence interval, 0.76-0.89), which indicated strong discrimination.

CONCLUSION

The obstetric comorbidity index can prospectively identify women at risk of severe maternal morbidity in a clinical setting. A particular strength of the obstetric comorbidity index is its ability to integrate multiple compounding comorbidities and highlight the cumulative risk that is associated with the patients' conditions. Routine clinical use of the obstetric comorbidity index has the potential to identify at-risk women whose condition warrants increased surveillance and targeted care to prevent adverse maternal outcomes.

Relationship between endogenous melatonin concentrations and uterine contractions in late third trimester of human pregnancy

In humans, circulating levels of the hormone melatonin and the initiation of spontaneous labor are both higher at night than during the day. Since activation of uterine melatonin receptors can stimulate human in vitro uterine contractions and these receptors are only expressed on the uterine tissue of women in labor, we hypothesized that circulating melatonin concentrations would affect uterine contractions in vivo. We evaluated the impact of light-induced modulation of melatonin secretion on uterine contractions in women during late third trimester (~36-39 weeks) of pregnancy in two inpatient protocols. We found a significant (P < 0.05) positive linear association between circulating melatonin concentrations and the number of uterine contractions under both protocols. On average, uterine contractions increased between 1.4 and 2.1 contractions per 30 minutes for every 10 pg/mL*h increase in melatonin concentration. These findings have both basic science and clinical implications for pregnant women, since endogenous melatonin levels and melatonin receptor activity can be altered by light and/or pharmaceutical agents.

Timing of Antenatal Corticosteroid Administration in Monoamniotic Twins

Objective  This study was aimed to determine if different strategies of antenatal corticosteroid (ACS) administration in monoamniotic twins leads to receipt within 7 days of delivery. Study Design  This is a retrospective cohort of monoamniotic twins managed at a single institution from 2007 to 2017. Patients were classified as to whether ACS were administered upon admission or at a predetermined gestational age (grouped together as "routine") or for a change in clinical status ("indicated"). We used univariate analyses to associate ACS administration strategies with our primary outcome: receipt of ACS within 7 days of delivery. We then used generalized estimating equations to examine associations between fetal monitoring patterns and delivery within 1 week. Results  Twenty-four patients were included: eighteen patients in the "routine" group and six patients in the "indicated" group. There was no difference in optimal timing of ACS administration. Women experiencing delivery within the week were thrice more likely to spend on average more than 3 hours/day on the fetal monitor when compared with those who remained undelivered. Conclusion  Administration of ACS on admission is not effective. Fetal heart rate tracing surveillance might be a better methodology to predict delivery and guide ACS administration.

Use of a Fibrin Sealant Patch at Cesarean for Conservative Management of Morbidly Adherent Placenta

Background  Morbidly adherent placenta represents a surgical challenge and source of maternal morbidity and mortality. We report the use of a fibrin sealant patch to address hemorrhage associated with a morbidly adherent placenta during cesarean delivery. Case  A patient underwent repeat cesarean delivery with complete anterior placenta previa and anticipated morbidly adherent placenta. Bleeding persisted following delivery and removal of the placenta, despite uterine artery embolization. A fibrin sealant patch was applied as an adjuvant intervention to the placental bed and hemostasis was achieved without resorting to a hysterectomy. Conclusion  Postpartum hemorrhage is an ongoing leading source of maternal morbidity and mortality. A case is presented in which a fibrin sealant patch provided control of focal placental bed bleeding, allowing removal of a focal morbidly adherent placenta and avoidance of hysterectomy.

Obstetric History and Likelihood of Preterm Birth of Twins

OBJECTIVE

The objective of this study was to investigate the relationship between preterm birth in a prior pregnancy and preterm birth in a twin pregnancy.

STUDY DESIGN

We performed a secondary analysis of a randomized controlled trial evaluating 17-α-hydroxyprogesterone caproate in twins. Women were classified as nulliparous, multiparous with a prior term birth, or multiparous with a prior preterm birth. We used logistic regression to examine the odds of spontaneous preterm birth of twins before 35 weeks according to past obstetric history.

RESULTS

Of the 653 women analyzed, 294 were nulliparas, 310 had a prior term birth, and 49 had a prior preterm birth. Prior preterm birth increased the likelihood of spontaneous delivery before 35 weeks (adjusted odds ratio [aOR]: 2.44, 95% confidence interval [CI]: 1.28-4.66), whereas prior term delivery decreased these odds (aOR: 0.55, 95% CI: 0.38-0.78) in the current twin pregnancy compared with the nulliparous reference group. This translated into a lower odds of composite neonatal morbidity (aOR: 0.38, 95% CI: 0.27-0.53) for women with a prior term delivery.

CONCLUSION

For women carrying twins, a history of preterm birth increases the odds of spontaneous preterm birth, whereas a prior term birth decreases odds of spontaneous preterm birth and neonatal morbidity for the current twin pregnancy. These results offer risk stratification and reassurance for clinicians.

Outcomes of Spontaneous Labor in Women Undergoing Trial of Labor after Cesarean as Compared with Nulliparous Women: A Retrospective Cohort Study

OBJECTIVE

The objective of this study was to compare spontaneous labor outcomes in women undergoing trial of labor after cesarean (TOLAC) and nulliparas to better counsel women.

STUDY DESIGN

A 4-year retrospective cohort. We included women at term in spontaneous labor with vertex singletons and no more than one prior cesarean delivery. In planned secondary analysis, we focused on a subset of women with a prior cesarean and a predicted likelihood of a successful vaginal delivery of 70% or more based on the Maternal-Fetal Medicine Units-vaginal birth after cesarean (VBAC) calculator.

RESULTS

Our cohort included 606 TOLACS and 606 nulliparas. Women undergoing TOLAC were more likely to undergo cesarean delivery (25.7 vs. 14.7%; p < 0.001). Severe maternal hemorrhage (1.5 vs. 0.2%; p = 0.02) and uterine rupture (1.9 vs. 0.0%; p < 0.01) were more likely in the TOLAC group. For the subset of women with a predicted likelihood of VBAC of 70% or more, there were no differences in cesarean delivery (16.7 vs. 14.7%; p = 0.51), maternal, or immediate neonatal complications.

CONCLUSION

Women undergoing TOLAC were more likely to have a cesarean delivery, hemorrhage, or uterine rupture. Those with more than 70% predicted likelihood of VBAC were no more likely to experience these outcomes. These findings help contextualize the risks of TOLAC for women considering this option.

The relative effects of patient and hospital factors on postpartum readmissions

OBJECTIVE

To determine the relative effects of patient and hospital factors on a hospital's postpartum readmission rate.

STUDY DESIGN

This retrospective cohort study was conducted using State Inpatient Databases from California, Florida, and New York between 2004 and 2013. We compared patient and hospital characteristics among hospitals with low and high readmission rates using χ² tests. Risk-adjusted 30-day readmission rates were calculated for patient, delivery, and hospital characteristics to understand factors affecting readmission using fixed and random effects models.

RESULTS

Patients in hospitals with low readmission rates were more likely to be white, to have private insurance and higher incomes, and to have fewer comorbidities. The patient comorbidities with the highest risk-adjusted readmission rates included hypertension (range, 2.14-3.04%), obesity (1.78-2.94%), preterm labor/delivery (2.50-2.60%), and seizure disorder (1.78-3.35%). Delivery complications were associated with increased risk-adjusted readmission rates. Compared to patient characteristics, hospital characteristics did not have a profound impact on readmission risk.

CONCLUSION

Obstetric readmissions were more attributable to patient and demographic characteristics than to hospital characteristics. Readmission metric-based incentives may ultimately penalize hospitals providing high-quality care due to patient characteristics specific to their catchment area.

Angle of Progression on Ultrasound in the Second Stage of Labor and Spontaneous Vaginal Delivery

OBJECTIVE

 The objective of this study was to assess the association between the angle of progression (AoP) measured by transperineal ultrasound and mode of delivery and duration of the second stage.

STUDY DESIGN

 This is a prospective observational study of nulliparous women with a singleton gestation at term in which serial transperineal ultrasound examinations were obtained during the second stage of labor. Multivariable logistic regression and adjusted survival models were used for the analysis.

RESULTS

 A total of 137 patients were included in the analysis and median AoP for the study group was 153 degrees. The adjusted odds ratio (aOR) of requiring an operative delivery was 2.6 times higher for those patients who had an AoP < 153 degrees and the aOR of requiring a cesarean delivery was almost six times higher when compared with those patients who had an AoP ≥ 153 degrees (95% confidence interval [CI]: 1.0, 6.2; p = 0.04; aOR: 5.8, 95% CI: 1.2-28.3; p = 0.03, respectively). Those patients with an AoP < 153 degrees were at a higher hazard of staying pregnant longer (adjusted hazard ratio: 1.8, 95% CI: 1.2-2.8, p = 0.005).

CONCLUSION

 The AoP has the potential to predict spontaneous vaginal delivery and the duration of the second stage of labor which may be useful in counseling patients and managing their labor.

The U.S. Twin Delivery Volume and Association with Cesarean Delivery Rates: A Hospital-Level Analysis

OBJECTIVE

 The objective of this study was to test whether hospitals experienced in twin delivery have lower rates of cesarean delivery for twins.

METHODS

 We divided obstetric hospitals in the 2011 National Inpatient Sample by quartile of annual twin deliveries and compared twin cesarean delivery rates between hospitals with weighted linear regression. We used Pearson's coefficients to correlate a hospital's twin cesarean delivery rate to its overall cesarean delivery and vaginal birth after cesarean (VBAC) rates.

RESULTS

 Annual twin delivery volume ranged from 1 to 506 across the 547 analyzed hospitals with a median of 10 and mode of 3. Adjusted rates of cesarean delivery were independent of delivery volume with a rate of 75.5 versus 74.8% in the lowest and highest volume hospitals (p = 0.09 across quartiles). A hospital's cesarean delivery rate for twins moderately correlated with the overall cesarean rate (r = 0.52, p < 0.01) and inversely correlated with VBAC rate (r =  - 0.42, p < 0.01).

CONCLUSION

 Most U.S. obstetrical units perform a low volume of twin deliveries with no decrease in cesarean delivery rates at higher volume hospitals. Twin cesarean delivery rates correlate with other obstetric parameters such as singleton cesarean delivery and VBAC rates suggesting twin cesarean delivery rate is more closely related to a hospital's general obstetric practice than its twin delivery volume.

Intrapartum obstetric care in the United States military: Comparison of military and civilian care systems within TRICARE

BACKGROUND

Expectant mothers who are beneficiaries of TRICARE (universal insurance to United States Armed Services members and their dependents) can choose to receive care within direct (salary-based) or purchased (fee-for-service) care systems. We sought to compare frequency of intrapartum obstetric procedures and outcomes such as severe acute maternal morbidity (SAMM) and common postpartum complications between direct and purchased care systems within TRICARE.

METHODS

TRICARE (2006-2010) claims data were used to identify deliveries. Patient demographics, frequency of types of delivery (noninstrumental vaginal, cesarean, and instrumental vaginal), comorbid conditions, SAMM, and common postpartum complications were compared between the two systems of care. Multivariable models adjusted for patient clinical/demographic factors determined the odds of common complications and SAMM complications in purchased care compared with direct care.

RESULTS

A total of 440 138 deliveries were identified. Compared with direct care, purchased care had higher frequency (30.9% vs 25.8%, P<.001) and higher adjusted odds (aOR 1.37 [CI 1.34-1.38]) of cesarean delivery. In stratified analysis by mode of delivery, purchased care had lower odds of common complications for all modes of delivery (aOR[CI]:noninstrumental vaginal: 0.72 [0.71-0.74], cesarean: 0.71 [0.68-0.75], instrumental vaginal: 0.64 [0.60-0.68]) than direct care. However, purchased care had higher odds of SAMM complications for cesarean delivery (aOR 1.31 [CI 1.19-1.44]) compared with direct care.

CONCLUSION

Direct care has a higher vaginal delivery rate but also a higher rate of common complications compared with purchased care. Study of direct and purchased care systems in TRICARE may have potential use as a surrogate for comparing obstetric care between salary-based systems and fee-for-service systems in the United States.