Defining 'obstetric haemorrhage': Blood loss volume and severe morbidity

AIMS AND OBJECTIVES

Our goal is to describe the association between total quantitative blood loss (QBL) and risk of obstetric haemorrhage-related morbidity (OBH-M) to assess the utility of the current definition of obstetric haemorrhage (OBH).

METHODS

This was a retrospective cohort study completed of all patients who had a live delivery at the only urban safety-net hospital over a 2-year period from 2018 to 2019. We categorized deliveries into 10 equally sized deciles based on QBL and compared the proportion with OBH-M in each. Among the two deciles with the highest proportions of OBH-M, we stratified deliveries into seven groups of ascending intervals of 250cc QBL. Finally, we compared the positive predictive value (PPV) of the standard definition of OBH (QBL ≥ 1000cc) to a definition extrapolated from our stratified analysis. The primary outcome was proportion of deliveries within each QBL decile affected by OBH-M. The secondary outcome was PPV.

RESULTS

We found a significant increase in OBH-M from decile 9 (895-1201cc QBL) to decile 10 (1205-8325cc QBL) (p < 0.001). In our stratified analysis, we found QBL of 1500cc to be an inflection point for an increased proportion of OBH-M. Our secondary analysis showed an increased PPV for OBH-M using QBL of 1500cc (20.5%) compared with that of QBL 1000cc (9.8%).

CONCLUSIONS

Our findings suggest that a higher QBL threshold than the currently accepted definition of OBH is more predictive of OBH-M.

Development of a Maternal Equity Safety Bundle to Eliminate Racial Inequities in Massachusetts

OBJECTIVE

The PNQIN (Perinatal-Neonatal Quality Improvement Network of Massachusetts) sought to adapt the Reduction of Peripartum Racial and Ethnic Disparities Conceptual Framework and Maternal Safety Consensus Bundle by selecting and defining measures to create a bundle to address maternal health inequities in Massachusetts. This study describes the process of developing consensus-based measures to implement the PNQIN Maternal Equity Bundle across Massachusetts hospitals participating in the Alliance for Innovation on Maternal Health Initiative.

METHODS

Our team used a mixed-methods approach to create the PNQIN Maternal Equity Bundle through consensus including a literature review, expert interviews, and a modified Delphi process to compile, define, and select measures to drive maternal equity-focused action. Stakeholders were identified by purposive and snowball sampling and included obstetrician-gynecologists, midwives, nurses, epidemiologists, and racial equity scholars. Dedoose 9.0 was used to complete an inductive analysis of interview transcripts. A modified Delphi method was used to reach consensus on recommendations and measures for the PNQIN Maternal Equity Bundle.

RESULTS

Twenty-five interviews were completed. Seven themes emerged, including the need for 1) data stratification by race, ethnicity and language; 2) performance of a readiness assessment; 3) culture shift toward equity; 4) inclusion of antiracism and bias training; 5) addressing challenges of nonacademic hospitals; 6) a life-course approach; and 7) selection of timing of implementation. Twenty initial quality measures (structure, process, and outcome) were identified through expert interviews. Group consensus supported 10 measures to be incorporated into the bundle.

CONCLUSION

Structure, process, and outcome quality measures were selected and defined for a maternal equity safety bundle that seeks to create an equity-focused infrastructure and equity-specific actions at birthing facilities. Implementation of an equity-focused safety bundle at birthing facilities may close racial gaps in maternal outcomes.

Intrapartum Risk Factors and Prediction of Obstetric Hemorrhage-Related Morbidity

OBJECTIVE

 The aim of this study was to assess whether inclusion of intrapartum risk factors improves our obstetric hemorrhage risk stratification tool in predicting obstetric hemorrhage, transfusion, and related severe morbidity.

STUDY DESIGN

 This is a retrospective cohort study using all live deliveries at a single institution over a 2-year period (n = 5,332). Obstetric hemorrhage risk factors, hemorrhage burden, and severe maternal morbidity index outcomes were assessed through chart abstraction. Hemorrhage risk was assessed at (1) "time of admission" through chart abstraction and (2) "predelivery" by calculation after inclusion of all abstracted intrapartum risk factors. Admission high risk was compared with predelivery high risk for sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio in predicting obstetric hemorrhage, obstetric hemorrhage requiring transfusion, and obstetric hemorrhage-related severe morbidity. Significance levels were calculated using descriptive statistical methods including chi-squared tests and McNemar's tests.

RESULTS

 The sensitivities of the risk assessment tool using admission risk classification for high-risk patients is 25% for obstetric hemorrhage, 37% for obstetric hemorrhage requiring transfusion, and 22% for obstetric hemorrhage-related severe morbidity. After intrapartum factor inclusion, the sensitivities increase to 55% for obstetric hemorrhage, 59% for obstetric hemorrhage requiring transfusion, and 47% for obstetric hemorrhage-related severe morbidity. This "predelivery" risk assessment is significantly more sensitive across all three end points (p < 0.001 for all three outcomes). While the positive likelihood ratios for obstetric hemorrhage are equal on admission and predelivery (2.10 on admission and predelivery), they increase after intrapartum factor inclusion for obstetric hemorrhage requiring transfusion and obstetric hemorrhage-related severe morbidity (on admission, 2.74 and 1.6, respectively, and predelivery: 4.57 and 3.58, respectively).

CONCLUSION

 Inclusion of intrapartum risk factors increases the accuracy of this obstetric hemorrhage risk stratification tool in predicting patients requiring hemorrhage management with transfusion and obstetric hemorrhage-related severe morbidity.

KEY POINTS

· There are little data to validate intrapartum hemorrhage risk reassessment.. · Including intrapartum factors improves risk stratification for transfusion and related morbidity.. · Future research should clinically validate risk reassessment in the intrapartum period..

Racial and Ethnic Disparities in Maternal and Infant Outcomes Among Opioid-Exposed Mother-Infant Dyads in Massachusetts (2017-2019)

Objectives. To examine the extent to which differences in medication for opioid use disorder (MOUD) in pregnancy and infant neonatal opioid withdrawal syndrome (NOWS) outcomes are associated with maternal race/ethnicity.Methods. We performed a secondary analysis of a statewide quality improvement database of opioid-exposed deliveries from January 2017 to April 2019 from 24 hospitals in Massachusetts. We used multivariable mixed-effects logistic regression to model the association between maternal race/ethnicity (non-Hispanic White, non-Hispanic Black, or Hispanic) and prenatal receipt of MOUD, NOWS severity, early intervention referral, and biological parental custody at discharge.Results. Among 1710 deliveries to women with opioid use disorder, 89.3% (n = 1527) were non-Hispanic White. In adjusted models, non-Hispanic Black women (AOR = 0.34; 95% confidence interval [CI] = 0.18, 0.66) and Hispanic women (AOR = 0.43; 95% CI = 0.27, 0.68) were less likely to receive MOUD during pregnancy compared with non-Hispanic White women. We found no statistically significant associations between maternal race/ethnicity and infant outcomes.Conclusions. We identified significant racial/ethnic differences in MOUD prenatal receipt that persisted in adjusted models. Research should focus on the perspectives and treatment experiences of non-Hispanic Black and Hispanic women to ensure equitable care for all mother-infant dyads.

Obstetric Hemorrhage Risk Associated with Novel COVID-19 Diagnosis from a Single-Institution Cohort in the United States

OBJECTIVE

The study aimed to compare the quantitative blood loss (QBL) and hemorrhage-related outcomes of pregnant women with and without a coronavirus disease 2019 (COVID-19) diagnosis.

STUDY DESIGN

This retrospective cohort study of all live deliveries at Boston Medical Center between April 1, 2020 and July 22, 2020 compares the outcomes of pregnant women with a laboratory-confirmed COVID-19 positive diagnosis and pregnant women without COVID-19. The primary outcomes are QBL and obstetric hemorrhage. The secondary outcomes analyzed were a maternal composite outcome that consisted of obstetric hemorrhage, telemetry-level (intermediate care unit) or intensive care unit, transfusion, length of stay greater than 5 days, or intraamniotic infection, and individual components of the maternal composite outcome. Groups were compared using Student's t-test, Chi-squared tests, or Fisher's exact. Logistic regression was used to adjust for confounding variables.

RESULTS

Of 813 women who delivered a live infant between April 1 and July 22, 2020, 53 women were diagnosed with COVID-19 on admission to the hospital. Women with a COVID-19 diagnosis at their time of delivery were significantly more likely to identify as a race other than white (p = 0.01), to deliver preterm (p = 0.05), to be diagnosed with preeclampsia with severe features (p < 0.01), and to require general anesthesia (p < 0.01). Women diagnosed with COVID-19 did not have a significantly higher QBL (p = 0.64). COVID-19 positive pregnant patients had no increased adjusted odds of obstetric hemorrhage (adjusted odds ratio [aOR]: 0.41, 95% confidence interval [CI]: 0.17-1.04) and no increased adjusted odds of the maternal morbidity composite (aOR: 0.98, 95% CI: 0.50-1.93) when compared with those without a diagnosis of COVID-19.

CONCLUSION

Pregnant women with COVID-19 diagnosis do not have increased risk for obstetric hemorrhage, increased QBL or risk of maternal morbidity compared with pregnant women without a COVID-19 diagnosis. Further research is needed to describe the impact of a COVID-19 diagnosis on maternal hematologic physiology and pregnancy outcomes.

KEY POINTS

· Information about blood loss associated with peripartum COVID-19 is limited.. · COVID-19 diagnosis is not associated with increase in obstetric hemorrhage.. · COVID-19 diagnosis is not associated with increase in blood loss..

Maternal perceptions of the experience of attempted labor induction and medically elective inductions: analysis of survey results from listening to mothers in California

BACKGROUND

The rate of induction of labor in the U.S. has risen from 9.6% in 1990 to 25.7% in 2018, including 31.7% of first-time births. Recent studies that have examined inductions have been small qualitative studies or relied on either medical records or administrative data. This study examines induction from the perspective of those women who experienced it, with a particular focus on the prevalence and predictors of inductions for nonmedical indications, women's experience of pressure to induce labor and the relationship between the attempt to medically initiate labor and cesarean section.

METHODS

Study data are drawn from the 2119 respondents to the Listening to Mothers in California survey who were planning to have a vaginal birth in 2016. Mothers were asked if there had been an attempt to medically initiate labor, if it actually started labor, if they felt pressured to have the induction, if they had a cesarean and the reason for the induction. Reasons for induction were classified as either medically indicated or elective.

RESULTS

Almost half (47%) of our respondents indicated an attempt was made to medically induce their labor, and 71% of those attempts initiated labor. More than a third of the attempts (37%) were elective. Attempted induction overall was most strongly associated with giving birth at 41+ weeks (aOR 3.28; 95% C.I. 2.21-4.87). Elective inductions were more likely among multiparous mothers and in pregnancies at 39 or 40 weeks. The perception of being pressured to have labor induced was related to higher levels of education, maternal preference for less medical intervention in birth, having an obstetrician compared to a midwife and gestational ages of 41+ weeks. Cesarean birth was more likely in the case of overall induction (aOR 1.51; 95% C.I. 1.11-2.07) and especially following a failed attempt at labor induction (aOR 4.50; 95% C.I. 2.93-6.90).

CONCLUSION

Clinicians counselling mothers concerning the need for labor induction should be aware of mothers' perceptions about birth and engage in true shared decision making in order to avoid the maternal perception of being pressured into labor induction.

Interrupting the Pathway from Gestational Diabetes Mellitus to Type 2 Diabetes: The Role of Primary Care

OBJECTIVE

Our objective was to describe patient-, provider-, and health systems-level factors associated with likelihood of obtaining guideline-recommended follow-up to prevent or mitigate early-onset type 2 diabetes after a birth complicated by gestational diabetes mellitus (GDM).

METHODS

This study presents a retrospective cohort analysis of de-identified demographic and health care system characteristics, and clinical claims data for 12,622 women with GDM who were continuously enrolled in a large, national U.S. health plan from January 31, 2006, to September 30, 2012. Data were obtained from the OptumLabs Data Warehouse. We extracted 1) known predictors of follow-up (age, race, education, comorbidities, GDM severity); 2) novel factors that had potential as predictors (prepregnancy use of preventive measures and primary care, delivery hospital size); and 3) outcome variables (glucose testing within 1 and 3 years and primary care visit within 3 years after delivery).

RESULTS

Asian ethnicity, higher education, GDM severity, and delivery in a larger hospital predicted greater likelihood of post-GDM follow-up. Women with a prepregnancy primary care visit of any type were two to three times more likely to receive postpartum glucose testing and primary care at 1 year, and 3.5 times more likely to have obtained testing and primary care at 3 years after delivery.

CONCLUSIONS

A history of use of primary care services before a pregnancy complicated by GDM seems to enhance the likelihood of postdelivery surveillance and preventive care, and thus reduce the risk of undetected early-onset type 2 diabetes. An emphasis on promoting early primary care connections for women in their early reproductive years, in addition to its overall value, is a promising strategy for ensuring follow-up testing and care for women after complicated pregnancies that forewarn risk for later chronic illness. Health systems should focus on models of care that connect primary and reproductive/maternity care before, during, and long after pregnancies occur.

After Gestational Diabetes: Impact of Pregnancy Interval on Recurrence and Type 2 Diabetes

The contribution of pregnancy interval after gestational diabetes (GDM) to type 2 diabetes (T2DM) onset is a poorly understood but potentially modifiable factor for T2DM prevention. The purpose of this study was to assess the impact of GDM recurrence and/or delivery interval on follow-up care and T2DM onset in a sample of continuously insured women with a term livebirth within 3 years of a GDM-affected delivery. This is a secondary analysis of a cohort of 12,622 women with GDM, 2006–2012, drawn from a national administrative data system (OptumLabs Data Warehouse). We followed 1091 women with GDM who had a subsequent delivery within 3 years of their index delivery. GDM recurred in 49.3% of subsequent pregnancies regardless of the interval to the next conception. Recurrence tripled the odds of early T2DM onset within 3 years of the second delivery. Women with GDM recurrence had greater likelihood of glucose testing in that 3-year interval, but not transition to primary care for continued monitoring, as required by both American Congress of Obstetricians and Gynecologists (ACOG) and the American Diabetes Association (ADA) guidelines. In multivariable analysis, we found a trend toward increased likelihood of T2DM onset for short interpregnancy intervals (≤1 year vs. 3 year, 0.08). Pregnancy interval may play a previously unrecognized role in progression to T2DM. T2DM onset after GDM can be prevented or mitigated, but many women in even this insured sample did not receive recommended follow-up monitoring and preventive care, even after a GDM recurrence. The postpartum visit may be an ideal time to inform patients about T2DM prevention opportunities, and discuss potential benefits of optimal spacing of future pregnancies.

Onset of T2DM after gestational diabetes: What the prevention paradox tells us about risk

This study investigates the effect of severity of gestational diabetes (GDM) on likelihood of post-delivery glucose testing and early onset Type 2 diabetes (T2DM). We asked if clinical focus on relative risk (RR), i.e. greater probability of T2DM onset in a higher-severity group, contributes to missed opportunities for prevention among women with lower-severity GDM. A sample of 12,622 continuously-insured women with GDM (2006-2015) was drawn from a large national dataset (OptumLabs® Data Warehouse) and followed for 3-years post-delivery. Higher-severity GDM was defined as addition of hypoglycemic therapy to standard of care for GDM. We found that women with higher-severity (n = 2627) were twice as likely as lower-severity women (n = 9995) to obtain glucose testing post-delivery. Moreover, 357 (13.6%) of the higher-severity women developed T2DM by year-3 vs. 600 (6.0%) lower-severity women. In an analysis of the population attributable fraction (PAF), defined as the contribution of excess risk to population prevalence, lower-severity women contributed more cases to diabetes rates than higher-risk women (PAF 79% vs. 21%), despite an increased RR in the higher-severity group (13.6% vs. 6.0%, RR 2.26, 95%CI 2.00, 2.56). Projecting out to the 327,950 U.S. deliveries in 2014, we estimate that 9277 higher-severity women (13.6%) and 15,584 lower-severity women (6.0%), will have developed T2DM by 2018. These data demonstrate that lower-severity GDM contributes substantially to the diabetes epidemic. Greater awareness of clinical and cost implications of gaps in follow-up for lower-severity GDM may strengthen the likelihood of post-delivery testing and primary care referral, and thus reinforce the path to prevention.

Follow-up after gestational diabetes: a fixable gap in women's preventive healthcare

OBJECTIVE

Gestational diabetes mellitus (GDM) is a known harbinger of future type 2 diabetes mellitus (T2DM), hypertension, and cardiac disease. This population-based study was designed to identify gaps in follow-up care relevant to prevention of T2DM in a continuously insured sample of women diagnosed with GDM.

RESEARCH DESIGN AND METHODS

We analyzed data spanning 2005-2015 from OptumLabs Data Warehouse, a comprehensive, longitudinal, real-world data asset with deidentified lives across claims and clinical information, to describe patterns of preventive care after GDM. Women with GDM were followed, from 1 year preconception through 3 years postdelivery to identify individual and healthcare systems characteristics, and report on GDM-related outcomes: postpartum glucose testing, transition to primary care for monitoring, GDM recurrence, and T2DM onset.

RESULTS

Among 12 622 women with GDM, we found low rates of glucose monitoring in the recommended postpartum period (5.8%), at 1 year (21.8%), and at 3 years (51%). A minority had contact with primary care postdelivery (5.7% at 6 months, 13.2% at 1 year, 40.5% at 3 years). Despite increased population risk (GDM recurrence in 52.2% of repeat pregnancies, T2DM onset within 3 years in 7.6% of the sample), 70.1% of GDM-diagnosed women had neither glucose testing nor a primary care visit at 1 year and 32.7% had neither at 3 years.

CONCLUSIONS

We found low rates of glucose testing and transition to primary care in this group of continuously insured women with GDM. Despite continuous insurance coverage, many women with a pregnancy complication that portends risk for future chronic illness fail to obtain follow-up testing and may have difficulty navigating between clinician specialties. Results point to a need for action to close the gap between obstetrics and primary care to ensure receipt of preventive monitoring as recommended by both the American Diabetes Association and the American Congress of Obstetricians and Gynecologists.

Early pregnancy vitamin D status and risk of preeclampsia

BACKGROUND

Low vitamin D status in pregnancy was proposed as a risk factor of preeclampsia.

METHODS

We assessed the effect of vitamin D supplementation (4,400 vs. 400 IU/day), initiated early in pregnancy (10-18 weeks), on the development of preeclampsia. The effects of serum vitamin D (25-hydroxyvitamin D [25OHD]) levels on preeclampsia incidence at trial entry and in the third trimester (32-38 weeks) were studied. We also conducted a nested case-control study of 157 women to investigate peripheral blood vitamin D-associated gene expression profiles at 10 to 18 weeks in 47 participants who developed preeclampsia.

RESULTS

Of 881 women randomized, outcome data were available for 816, with 67 (8.2%) developing preeclampsia. There was no significant difference between treatment (N = 408) or control (N = 408) groups in the incidence of preeclampsia (8.08% vs. 8.33%, respectively; relative risk: 0.97; 95% CI, 0.61-1.53). However, in a cohort analysis and after adjustment for confounders, a significant effect of sufficient vitamin D status (25OHD ≥30 ng/ml) was observed in both early and late pregnancy compared with insufficient levels (25OHD <30 ng/ml) (adjusted odds ratio, 0.28; 95% CI, 0.10-0.96). Differential expression of 348 vitamin D-associated genes (158 upregulated) was found in peripheral blood of women who developed preeclampsia (FDR <0.05 in the Vitamin D Antenatal Asthma Reduction Trial [VDAART]; P < 0.05 in a replication cohort). Functional enrichment and network analyses of this vitamin D-associated gene set suggests several highly functional modules related to systematic inflammatory and immune responses, including some nodes with a high degree of connectivity.

CONCLUSIONS

Vitamin D supplementation initiated in weeks 10-18 of pregnancy did not reduce preeclampsia incidence in the intention-to-treat paradigm. However, vitamin D levels of 30 ng/ml or higher at trial entry and in late pregnancy were associated with a lower risk of preeclampsia. Differentially expressed vitamin D-associated transcriptomes implicated the emergence of an early pregnancy, distinctive immune response in women who went on to develop preeclampsia.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00920621.

FUNDING

Quebec Breast Cancer Foundation and Genome Canada Innovation Network. This trial was funded by the National Heart, Lung, and Blood Institute. For details see Acknowledgments.

Prepregnancy Obesity and Primary Cesareans among Otherwise Low-Risk Mothers in 38 U.S. States in 2012

BACKGROUND

The United States has recently experienced increases in both its rate of obesity and its cesarean rate. Our objective was to use a new item measuring prepregnancy body mass index (BMI) on the U.S. Standard Certificate of Live Birth to examine at a population level the relationship between maternal obesity and primary cesarean delivery for women at otherwise low risk for cesarean delivery.

METHODS

By 2012, 38 states with 86 percent of United States births had adopted the U.S. Standard Certificate. The sample was limited to the 2,233,144 women who had a singleton, vertex, term (37-41 weeks) birth in 2012 and no prior cesarean. We modeled the likelihood of a primary cesarean by BMI category, controlling for maternal socio-demographic and medical characteristics.

RESULTS

Overall, 46.4 percent of otherwise low-risk mothers had a prepregnancy BMI in the overweight (25.1%) or obese (21.3%) categories, with the obese category distributed as follows: obese I (BMI 30.0-34.9, 12.4%); obese II (BMI 35.0-39.9, 5.5%); and obese III (BMI 40+, 3.5%). Obesity rates were highest among American Indian and Alaska Native (32.5%) and non-Hispanic black mothers (30.5%). After adjustment for demographic and medical risks, the adjusted risk ratios (95% confidence intervals) of cesarean for low-risk primiparas were: 1.61 (1.60-1.63) for obese I, 1.86 (1.83-1.88) for obese II, and 2.21 (2.18-2.25) for obese III mothers compared with mothers in the normal weight category.

DISCUSSION

A relationship between prepregnancy obesity and primary cesarean delivery among relatively low-risk mothers remained even after controlling for social and medical risk factors.

Follow-up of gestational diabetes mellitus in an urban safety net hospital: missed opportunities to launch preventive care for women

BACKGROUND

Our study assessed the follow-up of gestational diabetes mellitus (GDM) in the postpartum period among a racially and ethnically diverse group of women receiving care in a major urban medical center.

METHODS

We conducted cross-sectional analysis of clinical and administrative data on women aged 18-44 years who gave birth at Boston Medical Center (BMC) between 2003 and 2009, had GDM, and used BMC for regular care. We calculated the rate of glucose testing by 70 days and by 180 days after delivery and used logistic regression to assess the predictors of testing.

RESULTS

By 6 months postpartum, only 23.4% of GDM-affected women received any kind of glucose test. Among these, over half had been completed by 10 weeks but only 29% were the recommended oral glucose tolerance test (OGTT). After accounting for sociodemographic and health service factors, women aged ≤ 35 years of age and women with a family practice provider were significantly less likely to be tested than their counterparts (odds ratio [OR] 0.51; 95% confidence interval [CI] 0.32, 0.83 and OR 0.36; 95% CI 0.19, 0.71 respectively). Women who attended a primary care visit within 180 days after birth had three times higher odds of being tested than those without such a visit (OR 3.10; 95% CI 1.97, 4.87).

CONCLUSIONS

Despite widely disseminated clinical guidelines, postpartum glucose testing rates are exceedingly low, marking a critical missed opportunity to launch preventive care for women at high risk of type 2 DM. Failed follow-up of GDM by providers of prenatal and postpartum care also reflects a broader systems failure: the absence of a well-supported transition from pregnancy care to ongoing primary care for women.

Measurements and simulations of ultralow emittance and ultrashort electron beams in the linac coherent light source

The Linac Coherent Light Source (LCLS) is an x-ray free-electron laser project presently in a commissioning phase at the SLAC National Accelerator Laboratory. We report here on very low-emittance measurements made at low bunch charge, and a few femtosecond bunch length produced by the LCLS bunch compressors. Start-to-end simulations associated with these beam parameters show the possibilities of generating hundreds of GW at 1.5 A x-ray wavelength and nearly a single longitudinally coherent spike at 1.5 nm with 2-fs duration.

Measurement of the e;{+}e;{-}-->bb[over ] Cross Section between sqrt[s]=10.54 and 11.20 GeV

We report e;{+}e;{-}-->bb[over ] cross section measurements by the BABAR experiment performed during an energy scan in the range of 10.54 to 11.20 GeV at the SLAC PEP-II e;{+}e;{-} collider. A total relative error of about 5% is reached in more than 300 center-of-mass energy steps, separated by about 5 MeV. These measurements can be used to derive precise information on the parameters of the Upsilon(10860) and Upsilon(11020) resonances. In particular we show that their widths may be smaller than previously measured.

Observation of the bottomonium ground state in the decay Upsilon(3S)-->gammaetab

We report the results of a search for the bottomonium ground state etab(1S) in the photon energy spectrum with a sample of (109+/-1) million of Upsilon(3S) recorded at the Upsilon(3S) energy with the BABAR detector at the PEP-II B factory at SLAC. We observe a peak in the photon energy spectrum at Egamma=921.2(-2.8)+2.1(stat)+/-2.4(syst) MeV with a significance of 10 standard deviations. We interpret the observed peak as being due to monochromatic photons from the radiative transition Upsilon(3S)-->gammaetab(1S). This photon energy corresponds to an etab(1S) mass of 9388.9(-2.3)+3.1(stat)+/-2.7(syst) MeV/c2. The hyperfine Upsilon(1S)-etab(1S) mass splitting is 71.4(-3.1)+2.3(stat)+/-2.7(syst) MeV/c2. The branching fraction for this radiative Upsilon(3S) decay is estimated to be [4.8+/-0.5(stat)+/-1.2(syst)]x10(-4).

Observation of polarized positrons from an undulator-based source

An experiment (E166) at the Stanford Linear Accelerator Center has demonstrated a scheme in which a multi-GeV electron beam passed through a helical undulator to generate multi-MeV, circularly polarized photons which were then converted in a thin target to produce positrons (and electrons) with longitudinal polarization above 80% at 6 MeV. The results are in agreement with GEANT4 simulations that include the dominant polarization-dependent interactions of electrons, positrons, and photons in matter.

Positron production by x rays emitted by betatron motion in a plasma wiggler

Positrons in the energy range of 3-30 MeV, produced by x rays emitted by betatron motion in a plasma wiggler of 28.5 GeV electrons from the SLAC accelerator, have been measured. The extremely high-strength plasma wiggler is an ion column induced by the electron beam as it propagates through and ionizes dense lithium vapor. X rays in the range of 1-50 MeV in a forward cone angle of 0.1 mrad collide with a 1.7 mm thick tungsten target to produce electron-positron pairs. The positron spectra are found to be strongly influenced by the plasma density and length as well as the electron bunch length. By characterizing the beam propagation in the ion column these influences are quantified and result in excellent agreement between the measured and calculated positron spectra.

Hose instability and wake generation by an intense electron beam in a self-ionized gas

The propagation of an intense relativistic electron beam through a gas that is self-ionized by the beam's space charge and wakefields is examined analytically and with 3D particle-in-cell simulations. Instability arises from the coupling between a beam and the offset plasma channel it creates when it is perturbed. The traditional electron hose instability in a preformed plasma is replaced with this slower growth instability depending on the radius of the ionization channel compared to the electron blowout radius. A new regime for hose stable plasma wakefield acceleration is suggested.

Plasma wakefield acceleration in self-ionized gas or plasmas

Tunnel ionizing neutral gas with the self-field of a charged particle beam is explored as a possible way of creating plasma sources for a plasma wakefield accelerator [Bruhwiler et al., Phys. Plasmas (to be published)]. The optimal gas density for maximizing the plasma wakefield without preionized plasma is studied using the PIC simulation code OSIRIS [R. Hemker et al., in Proceeding of the Fifth IEEE Particle Accelerator Conference (IEEE, 1999), pp. 3672-3674]. To obtain wakefields comparable to the optimal preionized case, the gas density needs to be seven times higher than the plasma density in a typical preionized case. A physical explanation is given.

Plasma-wakefield acceleration of an intense positron beam

Plasma wakefields are both excited and probed by propagating an intense 28.5 GeV positron beam through a 1.4 m long lithium plasma. The main body of the beam loses energy in exciting this wakefield while positrons in the back of the same beam can be accelerated by the same wakefield as it changes sign. The scaling of energy loss with plasma density as well as the energy gain seen at the highest plasma density is in excellent agreement with simulations.

Ultrarelativistic-positron-beam transport through meter-scale plasmas

We report on the first study of the dynamic transverse forces imparted to an ultrarelativistic positron beam by a long plasma in the underdense regime. Focusing of the 28.5 GeV beam is observed from time-resolved beam profiles after the 1.4 m plasma. The strength of the imparted force varies along the approximately 12 ps full length of the bunch as well as with plasma density. Computer simulations substantiate the longitudinal aberration seen in the data and reveal mechanisms for emittance degradation.

Transverse envelope dynamics of a 28.5-GeV electron beam in a long plasma

The transverse dynamics of a 28.5-GeV electron beam propagating in a 1.4 m long, (0-2)x10(14) cm(-3) plasma are studied experimentally in the underdense or blowout regime. The transverse component of the wake field excited by the short electron bunch focuses the bunch, which experiences multiple betatron oscillations as the plasma density is increased. The spot-size variations are observed using optical transition radiation and Cherenkov radiation. In this regime, the behavior of the spot size as a function of the plasma density is well described by a simple beam-envelope model. Dynamic changes of the beam envelope are observed by time resolving the Cherenkov light.

Observation of plasma focusing of a 28.5 GeV positron beam

The observation of plasma focusing of a 28.5 GeV positron beam is reported. The plasma was formed by ionizing a nitrogen jet only 3 mm thick. Simultaneous focusing in both transverse dimensions was observed with effective focusing strengths of order tesla per micron. The minimum area of the beam spot was reduced by a factor of 2.0+/-0.3 by the plasma. The longitudinal beam envelope was measured and compared with numerical calculations.

Measurements of radiation near an atomic spectral line from the interaction of a 30 GeV electron beam and a long plasma

Emissions produced or initiated by a 30-GeV electron beam propagating through a approximately 1-m long heat pipe oven containing neutral and partially ionized vapor have been measured near atomic spectral lines in a beam-plasma wakefield experiment. The Cerenkov spatial profile has been studied as a function of oven temperature and pressure, observation wavelength, and ionizing laser intensity and delay. The Cerenkov peak angle is affected by the creation of plasma, and estimates of neutral and plasma density have been extracted. Increases in visible background radiation, consistent with increased plasma recombination emissions due to dissipation of wakefields, were simultaneously measured.

Observation of the Askaryan effect: coherent microwave Cherenkov emission from charge asymmetry in high-energy particle cascades

We present the first direct experimental evidence for the charge excess in high-energy particle showers and corresponding radio emission predicted nearly 40 years ago by Askaryan. We directed picosecond pulses of GeV bremsstrahlung photons at the SLAC Final Focus Test Beam into a 3.5 ton silica sand target, producing electromagnetic showers several meters long. A series of antennas spanning 0.3 to 6 GHz detected strong, subnanosecond radio-frequency pulses produced by the showers. Measurements of the polarization, coherence, timing, field strength vs shower depth, and field strength vs frequency are completely consistent with predictions. These measurements thus provide strong support for experiments designed to detect high-energy cosmic rays such as neutrinos via coherent radio emission from their cascades.

Rapidly progressive aphasic dementia and motor neuron disease

Articulatory and language impairment heralded rapidly progressive motor neuron disease in 7 patients aged 54 to 77 years. One patient had a family history of a similar disorder. Severe nonfluent aphasia developed in all 7 patients and 4 were anarthric within a year. Other cognitive domains were impaired, yet 2 patients lived alone until 1 month before their deaths. Four died within 2 years. Abnormalities were found on electromyography, computed tomography, magnetic resonance imaging, single-photon emission computed tomography, and electroencephalography. Neuropathological examination in 3 patients showed bilateral hemispheric atrophy with neuronal loss and gliosis predominantly of superficial cortical layers. Pigmented and hypoglossal nuclei were relatively preserved. At all spinal levels there was degeneration of corticospinal tracts and loss of anterior horn cells with gliosis. Rapidly progressive aphasic dementia and motor neuron disease are a distinctive clinical entity whose nosology is poorly understood.

Effects of alterations in pulmonary function and sleep variables on survival in patients with amyotrophic lateral sclerosis

Breathing abnormalities and nocturnal hypoventilation occur in patients with amyotrophic lateral sclerosis (ALS). A prospective study was undertaken to determine the relationship of pulmonary function test abnormalities with quality of sleep and survival in 21 patients with ALS. Results of spirometry including determination of maximal respiratory pressures and arterial blood gases were compared with several formal polysomnographic variables and then also with 18-month survival. The patients had mild to moderate pulmonary function deficits, but the quality of sleep was best related to age (mean age, 58.5 years). The results of pulmonary function tests and arterial blood gas measurements did not correlate well with the presence of nocturnal breathing events or survival time, but the maximal inspiratory pressure was 86% sensitive for predicting the presence of a nocturnal oxygen saturation nadir of 80% or less and 100% sensitive for predicting 18-month survival. Although obstructive breathing events occurred, the primary explanation for the decline in nocturnal oxygen saturation was hypoventilation. We conclude that routine pulmonary function tests may be useful for screening for reductions in nocturnal oxygen saturation and also may have prognostic value. Further studies may determine whether treatment of nocturnal hypoventilation will have an effect on survival in patients with ALS who have breathing impairment.

Late effects of paralytic poliomyelitis in Olmsted County, Minnesota

We identified a cohort of 300 individuals who had paralytic polio between 1935 and 1955. All lived in Olmsted County, Minnesota. From the 247 survivors, we selected 50 subjects for detailed historical, functional, psychological, clinical, and electrophysiologic evaluation. Sixty-four percent of these 50 survivors complained of new symptoms of muscle pain, fatigue, and weakness after a period of prolonged stability. This led to changes in lifestyle or activity in only 18%. The likelihood of expressing new complaints was not related to present age or interval since polio, and electrophysiologic testing did not distinguish between those with or without new problems. The development of new difficulties in a limb was most strongly predicted by significant paralysis of that limb at the time of the acute illness. Patients with leg weakness were twice as likely to complain of new problems compared to those with arm weakness. Elevated creatine kinase levels were present only in those with new complaints.

Effect of low frequency low energy pulsing electromagnetic field (PEMF) on X-ray-irradiated mice

C3H/Km flora-defined mice were used to investigate the effect of exposure to pulsing electromagnetic field (PEMF) after total body x-ray irradiation. Prolonged exposure to PEMF had no effect on normal nonirradiated mice. When mice irradiated with different doses of x-ray (8.5 Gy, 6.8 Gy, and 6.3 Gy) were exposed to PEMF 24 h a day, we observed a more rapid decline in white blood cells (WBC) in the peripheral blood of mice exposed to PEMF at all the x-ray dosages used. No effect of exposure to PEMF was observed on the survival of the mice irradiated with 6.3 Gy and 8.5 Gy; in mice irradiated with 6.8 Gy, 2 out of 12 survived when exposed to PEMF as compared to 10 out of 12 control mice that were irradiated only. At day 4 after irradiation autoradiographic studies performed on bone marrow and spleen of 8.5-Gy-irradiated mice showed no difference between controls and mice exposed to PEMF, whereas on 6.8-Gy mice the bone marrow labeling index was lower in mice exposed to PEMF. In mice irradiated to 6.3 Gy we observed that the recovery of WBC in the peripheral blood was slowed in mice exposed to PEMF and their body weight was significantly lower than in control mice that were irradiated only. The spleen and bone marrow of the mice irradiated to 6.3 Gy and sacrificed at days 4, 14, 20, and 25 after irradiation were analyzed by autoradiography to evaluate the labeling index. Half of the spleens from mice sacrificed at day 25 after irradiation were used to evaluate the RNA content. Autoradiography showed that in the spleen and bone marrow of control mice, there were more cells labeled with [3H]thymidine at days 4 and 14 and less at days 20 and 25 after irradiation in comparison with mice irradiated and exposed to PEMF. The Northern blot analysis of histone H3 and p53 protein RNAs extracted from the spleens at day 25 after irradiation showed a slight increase in cycling cells among spleens of mice exposed to PEMF. We suggest that the exposure to PEMF immediately after x-ray irradiation results in increased damage.

Metabolism of pregnenolone by human breast cancer. Evidence for 17 alpha-hydroxylase and 17,20-lyase

The metabolism of 7-(3)H-pregnenolone was studied in vitro using 16 human breast carcinomas. All mammary tumors transformed pregnenolone to progesterone. All estrogen receptor poor tumors and 4 out of 8 estrogen receptor rich tumors converted pregnenolone to 17-hydroxypregnenolone. Five estrogen receptor poor tumors showed the presence of 17,20-lyase as evidenced by formation of dehydroepiandrosterone and androstenedione. In two estrogen receptor poor tumors, conversions of pregnenolone to progesterone, 17-hydroxy pregnenolone, dehydroepiandrosterone, androstenedione and finally to estradiol was documented, providing a hypothetical pathway for steroid metabolism in human breast cancer. The conversion of pregnenolone to 17-hydroxypregnenolone was significantly less in receptor rich tumors and was totally absent in 4 receptor rich tumors with estrogen receptors of over 45 fmol/mg protein.

Estradiol 17 beta-dehydrogenase and estradiol binding in human mammary tumors

The metabolism of estradiol was studied in 31 human breast carcinoma in vitro. All 16 estrogen-receptor-poor tumors transformed estradiol to estrone with percent conversions ranging from 11.4 to 95 except for one poorly differentiated tumor where 0.5% conversion to estrone was observed. On the contrary, only 3 out of 15 estrogen-receptor-rich tumors showed higher than 10% conversion of estradiol to estrone (p = 0.001). There is indication that the enzymatic activity in receptor-poor tumors steadily decreases in premenopausal patients as they approach menopausal age, whereas, the activity steadily increases in post-menopausal patients as the duration of menopause lengthens.

Aromatization of androgens by human breast cancer

The metabolism of dehydroepiandrosterone and testosterone by human mammary tumor was investigated. Estrogen synthesis from dehydroepiandrosterone was observed in 9 of 10 estrogen-receptor-negative tumors and only in 2 of 8 receptor-positive tumors (p less than 0.025). Conversion of testosterone to estrogens was observed in 7 of 8 receptor-negative and 2 of 7 receptor-positive tumors. Tumors which are capable of transforming dehydroepiandrosterone to estrogens were also able to aromatize testosterone suggesting that the presence of the aromatase enzyme is inherent to certain tumor cells. No estrogen formation was detected by the mitochondrial-microsomal fraction of normal breast cells while fractions from both fat cell and tumor cell showed estrogen synthesis. Estrogen formation by tumor cell fraction ranged from 5 to 190 times that observed for fat cells. The physiological significance of these results in the neoplastic tissue and its relationship to hormone dependence are discussed.