Hospital Encounters Within 1 Year Postpartum Across Insurance Types, Oregon 2012-2017.

BACKGROUND: Little is known about the timing and frequency of postpartum hospital encounters and postpartum visit attendance and how they may be associated with insurance types. Research on health insurance and its association with postpartum care utilization is often limited to the first 6 weeks. OBJECTIVE: To assess whether postpartum utilization (hospital encounters within 1 year postpartum and postpartum visit attendance within 12 weeks) differs by insurance type at birth (Medicaid, high deductible health plans, and other commercial plans) and whether rates of hospital encounters differ by postpartum visit attendance and insurance status. METHODS: Time-to-event analysis of Oregon hospital births from 2012 to 2017 using All Payer All Claims data. We conducted weighted Cox Proportional Hazard regressions and accounted for differences in insurance type at birth using multinomial propensity scores. RESULTS: Among 202,167 hospital births, 24.9% of births had at least 1 hospital encounter within 1 year postpartum. Births funded by Medicaid had a higher risk of a postpartum emergency department (ED) visit (hazard ratio: 2.05, 95% CI: 1.99, 2.12) and lower postpartum visit attendance (hazard ratio: 0.71, 95% CI: 0.70, 0.72) compared with commercial plans. Among Medicaid beneficiaries, missing the postpartum visit in the first 6 weeks was associated with a lower risk of subsequent readmissions (adjusted hazard ratio 0.77, 95% CI: 0.68, 0.87) and ED visits (adjusted hazard ratio: 0.87 (0.85, 0.88). CONCLUSIONS: Medicaid beneficiaries received more care in the ED within 1 year postpartum compared with those enrolled in other commercial plans. This highlights potential issues in postpartum care access.

Pelvic floor dysfunction after intervention, compared with expectant management, in prolonged second stage of labour: A population-based questionnaire and cohort study.

OBJECTIVE: To investigate the effect of vacuum extraction (VE) or caesarean section (CS), compared with expectant management, on pelvic floor dysfunction (PFD) 1-2 years postpartum in primiparous women with a prolonged second stage of labour. DESIGN: A population-based questionnaire and cohort study. SETTING: Stockholm, Sweden. POPULATION: A cohort of 1302 primiparous women with a second stage duration of ≥3 h, delivering from December 2017 to November 2018. METHODS: The 1-year follow-up questionnaire from the Swedish National Perineal Laceration Register was distributed 12-24 months postpartum. Exposure was VE or CS at 3-4 h or 4-5 h, compared with expectant management. MAIN OUTCOME MEASURES: Pelvic floor dysfunction was defined as at least weekly symptoms of urinary incontinence, pelvic organ prolapse or a Wexner score of ≥4. The risk of PFD was calculated using Poisson regression with robust variance estimation, presented as crude and adjusted relative risks (RRs and aRRs) with 95% confidence intervals (95% CIs). The implication of obstetric anal sphincter injury (OASI) on pelvic floor disorders was investigated through mediation analysis. RESULTS: In total, 35.1% of women reported PFD. Compared with expectant management, the risk of PFD was increased after VE at 3-4 h (aRR 1.33, 95% CI 1.06-1.65) and 4-5 h (aRR 1.34, 95% CI 1.05-1.70), but remained unchanged after CS. The increased risk after VE was not mediated by OASI. CONCLUSIONS: Pelvic floor dysfunction was common in primiparous women after a prolonged second stage, and the risk of PFD increased after VE but was unaffected by CS, compared with expectant management. If a spontaneous vaginal delivery eventually occurred, allowing an extended duration of labour did not increase the risk of PFD.

Pregnancy health in a multi-state U.S. population of systemically underserved patients and their children: PROMISE cohort design and baseline characteristics.

BACKGROUND: Gestational weight gain (GWG) is a routinely monitored aspect of pregnancy health, yet critical gaps remain about optimal GWG in pregnant people from socially marginalized groups, or with pre-pregnancy body mass index (BMI) in the lower or upper extremes. The PROMISE study aims to determine overall and trimester-specific GWG associated with the lowest risk of adverse birth outcomes and detrimental infant and child growth in these underrepresented subgroups. This paper presents methods used to construct the PROMISE cohort using electronic health record data from a network of community-based healthcare organizations and characterize the cohort with respect to baseline characteristics, longitudinal data availability, and GWG. METHODS: We developed an algorithm to identify and date pregnancies based on outpatient clinical data for patients 15 years or older. The cohort included pregnancies delivered in 2005-2020 with gestational age between 20 weeks, 0 days and 42 weeks, 6 days; and with known height and adequate weight measures needed to examine GWG patterns. We linked offspring data from birth records and clinical records. We defined study variables with attention to timing relative to pregnancy and clinical data collection processes. Descriptive analyses characterize the sociodemographic, baseline, and longitudinal data characteristics of the cohort, overall and within BMI categories. RESULTS: The cohort includes 77,599 pregnancies: 53% had incomes below the federal poverty level, 82% had public insurance, and the largest race and ethnicity groups were Hispanic (56%), non-Hispanic White (23%) and non-Hispanic Black (12%). Pre-pregnancy BMI groups included 2% underweight, 34% normal weight, 31% overweight, and 19%, 8%, and 5% Class I, II, and III obesity. Longitudinal data enable the calculation of trimester-specific GWG; e.g., a median of 2, 4, and 6 valid weight measures were available in the first, second, and third trimesters, respectively. Weekly rate of GWG was 0.00, 0.46, and 0.51 kg per week in the first, second, and third trimesters; differences in GWG between BMI groups were greatest in the second trimester. CONCLUSIONS: The PROMISE cohort enables characterization of GWG patterns and estimation of effects on child growth in underrepresented subgroups, ultimately improving the representativeness of GWG evidence and corresponding guidelines.

Development of a University-Government Partnership for Public Health Response and Workforce Development in the State of Oregon.

The COVID-19 pandemic exposed and exacerbated a public health workforce shortage and national strategies have called for the development of clear occupational pathways for students to enter the public health workforce and meaningful public health careers. In response to the immediate need for public health workers during the pandemic, several universities and academic hospitals rapidly mobilized students and employees and partnered with local or state health departments. However, many of those partnerships were based on short-term volunteer effort to support critical COVID-19 public health efforts. In this article, we document the development of Oregon's Public Health Practice Team, a student, staff, and faculty workforce developed at the Oregon Health & Science University-Portland State University (OHSU-PSU) School of Public Health in close collaboration with the Oregon Health Authority (OHA). This project contributed significant effort to several phases of Oregon's statewide public health response to COVID-19, and over time developed into a lasting, multi-purpose, inter-agency collaborative public health practice program. Health equity has been centered at every stage of this work. We describe the phases of the partnership development, the current team structure and operations, and highlight key challenges and lessons learned. This provides a case-study of how an innovative and flexible university-government partnership can contribute to immediate pandemic response needs, and also support ongoing public health responses to emerging needs, while contributing to the development of a skilled and diverse public health workforce.

Postpartum Hospital Readmissions With and Without Severe Maternal Morbidity Within 1 Year of Birth, Oregon, 2012-2017.

Postpartum readmissions (PPRs) represent a critical marker of maternal morbidity after hospital childbirth. Most severe maternal morbidity (SMM) events result in a hospital admission, but most PPRs do not have evidence of SMM. Little is known about PPR and SMM beyond the first 6 weeks postpartum. We examined the associations of maternal demographic and clinical factors with PPR within 12 months postpartum. We categorized PPR as being with or without evidence of SMM to assess whether risk factors and timing differed. Using the Oregon All Payer All Claims database, we analyzed hospital births from 2012-2017. We used log-binomial regression to estimate associations between maternal factors and PPR. Our final analytical sample included 158,653 births. Overall, 2.6% (n = 4,141) of births involved at least 1 readmission within 12 months postpartum (808 (19.5% of PPRs) with SMM). SMM at delivery was the strongest risk factor for PPR with SMM (risk ratio (RR) = 5.55, 95% confidence interval (CI): 4.14, 7.44). PPR without SMM had numerous risk factors, including any mental health diagnosis (RR = 2.10, 95% CI: 1.91, 2.30), chronic hypertension (RR = 2.17, 95% CI: 1.85, 2.55), and prepregnancy diabetes (RR = 2.85, 95% CI: 2.47, 3.30), all which were on par with SMM at delivery (RR = 1.89, 95% CI: 1.49, 2.40).

Remapping racial and ethnic inequities in severe maternal morbidity: The legacy of redlining in California.

BACKGROUND: Historical mortgage redlining, a racially discriminatory policy designed to uphold structural racism, may have played a role in producing the persistently elevated rate of severe maternal morbidity (SMM) among racialised birthing people. OBJECTIVE: This study examined associations between Home-Owner Loan Corporation (HOLC) redlining grades and SMM in a racially and ethnically diverse birth cohort in California. METHODS: We leveraged a population-based cohort of all live hospital births at ≥20 weeks of gestation between 1997 and 2017 in California. SMM was defined as having one of 21 procedures and diagnoses, per an index developed by Centers for Disease Control and Prevention. We characterised census tract-level redlining using HOLC's security maps for eight California cities. We assessed bivariate associations between HOLC grades and participant characteristics. Race and ethnicity-stratified mixed effects logistic regression models assessed the risk of SMM associated with HOLC grades within non-Hispanic Black, Asian/Pacific Islander, American Indian/Alaskan Native and Hispanic groups, adjusting for sociodemographic information, pregnancy-related factors, co-morbidities and neighbourhood deprivation index. RESULTS: The study sample included 2,020,194 births, with 24,579 cases of SMM (1.2%). Living in a census tract that was graded as "Hazardous," compared to census tracts graded "Best" and "Still Desirable," was associated with 1.15 (95% confidence interval [CI] 1.03, 1.29) and 1.17 (95% CI 1.09, 1.25) times the risk of SMM among Black and Hispanic birthing people, respectively, independent of sociodemographic factors. These associations persisted after adjusting for pregnancy-related factors and neighbourhood deprivation index. CONCLUSIONS: Historical redlining, a tool of structural racism that influenced the trajectory of neighbourhood social and material conditions, is associated with increased risk of experiencing SMM among Black and Hispanic birthing people in California. These findings demonstrate that addressing the enduring impact of macro-level and systemic mechanisms that uphold structural racism is a vital step in achieving racial and ethnic equity in birthing people's health.

Estimating the effect of timing of earned income tax credit refunds on perinatal outcomes: a quasi-experimental study of California births.

BACKGROUND: The largest poverty alleviation program in the US is the earned income tax credit (EITC), providing $60 billion to over 25 million families annually. While research has shown positive impacts of EITC receipt in pregnancy, there is little evidence on whether the timing of receipt may lead to differences in pregnancy outcomes. We used a quasi-experimental difference-in-differences design, taking advantage of EITC tax disbursement each spring to examine whether trimester of receipt was associated with perinatal outcomes. METHODS: We conducted a difference-in-differences analysis of California linked birth certificate and hospital discharge records. The sample was drawn from the linked CA birth certificate and discharge records from 2007-2012 (N = 2,740,707). To predict eligibility, we created a probabilistic algorithm in the Panel Study of Income Dynamics and applied it to the CA data. Primary outcome measures included preterm birth, small-for-gestational age (SGA), gestational diabetes, and gestational hypertension/preeclampsia. RESULTS: Eligibility for EITC receipt during the third trimester was associated with a lower risk of preterm birth compared with preconception. Eligibility for receipt in the preconception period resulted in improved gestational hypertension and SGA. CONCLUSION: This analysis offers a novel method to impute EITC eligibility using a probabilistic algorithm in a data set with richer sociodemographic information relative to the clinical and administrative data sets from which outcomes are drawn. These results could be used to determine the optimal intervention time point for future income supplementation policies. Future work should examine frequent income supplementation such as the minimum wage or basic income programs.

Accurate identification of cohort study designs in perinatal research: a practical guide.

Study designs are often mischaracterized in the obstetrics literature; in particular, the designation of studies as retrospective (historical) cohorts is frequently in error to describe studies that are prospective cohorts. This is especially true for studies based on electronic health records, which often should be properly considered as prospective cohorts. Epidemiologic study designs were developed in earlier eras of research and healthcare when researchers directly contacted study participants or relied on data from paper medical records. Accordingly, standard epidemiologic study design definitions are difficult to apply to digitized data, which have become common in the modern era of healthcare and computing. In this article, we briefly review the characteristics of the 3 main types of cohort studies. Afterward, we build on existing definitions by proposing several subdesignations of prospective cohort studies that we believe will reduce the confusion in terminology. We provide illustrative examples from obstetrics to concretely demonstrate connections and distinctions among study designs. First, a prospective cohort study can be "active" (participants are deliberately and explicitly enrolled in a prospective research study) or "passive" (participants are followed up in real time for some nonresearch activity, such as clinical care or quality improvement). An active prospective cohort study never stops being a prospective cohort study; however, when reused to answer a new, secondary question, we propose that this should be called a "reused (active) prospective cohort." The de novo cohort study that answered the original question should be considered an "intended (active) prospective cohort." Lastly, when a randomized controlled trial is reused to study some new questions where the randomization variable is not under study, this is also a subtype of a prospective cohort study, a "repurposed randomized controlled trial." The use of more detailed descriptors to describe prospective cohort studies will enable more accurate identification of this study design going forward. It is likely that further refinements will be needed in the future, given the ongoing evolution of how we engage with patients or participants and how data are collected, stored, and linked.

Differences in Perinatal Outcomes of Birthing People in Same-Sex and Different-Sex Marriages.

It is unknown whether people in same-sex relationships who give birth have different perinatal outcomes than people in different-sex relationships, despite differences in risk factors such as use of assisted reproductive technologies, obesity, smoking, and poor mental health. Marriage equality has established birth certificates as a promising new source of population-based data on births to same-sex married parents. We used birth certificate data from Massachusetts for 201,873 singletons born to married parents from 2012 to 2016. We estimated the associations of several birth outcomes with having a birth parent in a same-sex marriage using propensity score-matched and -unmatched samples. We also tested whether these associations were modified by the use of assisted reproductive technologies. People in same-sex marriages who gave birth had perinatal outcomes related to decreased fetal growth and preterm birth that were similar to those of their peers in different-sex marriages. Use of assisted reproductive technology was associated with decreased fetal growth and increased risk of preterm birth for infants with different-sex parents but not for infants with same-sex parents. More research is needed across other states and to understand why use of assisted reproductive technology is not a risk factor for poor birth outcomes for those in same-sex marriages.

Severe Maternal Morbidity: A Comparison of Definitions and Data Sources.

Severe maternal morbidity (SMM) is a composite outcome measure that indicates serious, potentially life-threatening maternal health problems. There is great interest in defining SMM using administrative data for surveillance and research. In the United States, one common way of defining SMM at the population level is an index developed by the Centers for Disease Control and Prevention. Modifications to this index (e.g., exclusion of maternal blood transfusion) have been proposed; some research defines SMM using an index introduced by Bateman et al. (Obstet Gynecol. 2013;122(5):957-965). Birth certificate data are also increasingly being used to define SMM. We compared commonly used US definitions of SMM among all California births (2007-2012) using the kappa (κ) statistic and other measures. We also evaluated agreement between maternal morbidity fields on the birth certificate as compared with health insurance claims data. Concordance between the 7 definitions of SMM analyzed was generally low (i.e., κ < 0.41 for 13 of 21 two-way comparisons). Low concordance was particularly driven by the presence/absence of transfusion and claims data versus birth certificate definitions. Low agreement between administrative data-based definitions of SMM highlights that results can be expected to differ between them. Further research on validity of SMM definitions, using more fine-grained data sources, is needed.

Interpregnancy Interval and Subsequent Severe Maternal Morbidity: A 16-Year Population-Based Study From California.

Interpregnancy interval (IPI) is associated with adverse perinatal outcomes, but its contribution to severe maternal morbidity (SMM) remains unclear. We examined the association between IPI and SMM, using data linked across sequential pregnancies to women in California during 1997-2012. Adjusting for confounders measured in the index pregnancy (i.e., the first in a pair of consecutive pregnancies), we estimated adjusted risk ratios for SMM related to the subsequent pregnancy. We further conducted within-mother comparisons and analyses stratified by parity and maternal age at the index pregnancy. Compared with an IPI of 18-23 months, an IPI of <6 months had the same risk for SMM in between-mother comparisons (adjusted risk ratio (aRR) = 0.96, 95% confidence interval (CI): 0.91, 1.02) but lower risk in within-mother comparisons (aRR = 0.76, 95% CI: 0.67, 0.86). IPIs of 24-59 months and ≥60 months were associated with increased risk of SMM in both between-mother (aRR = 1.18 (95% CI: 1.13, 1.23) and aRR = 1.76 (95% CI: 1.68, 1.85), respectively) and within-mother (aRR = 1.22 (95% CI: 1.11, 1.34) and aRR = 1.88 (95% CI: 1.66, 2.13), respectively) comparisons. The association between IPI and SMM did not vary substantially by maternal age or parity. In this study, longer IPI was associated with increased risk of SMM, which may be partly attributed to interpregnancy health.

Occupational Noise Exposure and Longitudinal Hearing Changes in Post-9/11 US Military Personnel During an Initial Period of Military Service.

OBJECTIVES: Auditory impairments, particularly those resulting from hazardous occupational noise exposures, are pressing concerns for the US Departments of Defense (DoD) and Veterans Affairs (VA). However, to date, no studies have estimated the rate of hearing threshold change that occurs during service or how changes may vary by military occupation. Hearing threshold changes during military service have historically been reported as the proportion of Service members demonstrating a significant threshold shift. This approach does not capture the rate of the hearing threshold change or the specific audiometric frequencies impacted. Determining the rate of hearing threshold change, and factors that affect the rate of change, is important to elucidate the impact of military service on hearing and to guide prevention strategies and subsequent hearing health care. Our primary objective was to estimate the annual rate of hearing threshold change during military service as a consequence of military occupational noise exposure ranking. DESIGN: We linked audiometric data, collected from military personnel as part of a DoD hearing conservation program, to data describing demographic and military-service characteristics obtained from individuals enrolled in the Noise Outcomes In Service members Epidemiology Study. The analytic cohort included Veterans who enlisted in military service after September 2001 (n = 246). We examined the longitudinal association between military occupations categorized as having a low, moderate, or high noise exposure ranking and pure-tone hearing thresholds (500 to 6000 Hz) using a hierarchical linear model. The average annual rate of hearing threshold change and their 95% confidence intervals were estimated by service branch, military occupational noise exposure ranking, and audiometric test frequency. RESULTS: On average, hearing threshold change ranged between -0.5 and 1.1 dB/year and changes over time varied by service branch, audiometric test frequency, and military occupation noise ranking. Generally, higher test frequencies (3000 to 6000 Hz) and military occupations with moderate or high noise exposure rankings had the greatest average annual rates of hearing threshold change; however, no dose-response relationship was observed. Among Marine Corps personnel, those exposed to occupations with high noise rankings demonstrated the greatest average annual rate of change (1.1 dB/year at 6000 Hz). Army personnel exposed to occupations with moderate noise rankings demonstrated the greatest average annual rate of change (0.6 dB/year at 6000 Hz). CONCLUSIONS: This study (1) demonstrates the unique use of DoD hearing conservation program data, (2) is the first analysis of hearing threshold changes over time using such data, and (3) adds to the limited literature on longitudinal changes in hearing. The difference in hearing threshold changes across military branches is likely indicative of their varying noise exposures, hearing protection device use and enforcement, and surveillance practices. Results suggest Marine Corps and Army personnel are at risk for hearing threshold changes and that, among Army personnel, this is most pronounced among those exposed to moderate levels of occupational noise exposure. Estimates of the rate of hearing threshold change by frequency and factors that impact hearing are useful to inform the DoD's efforts to protect the hearing of their Service members and to the Veterans Affairs's efforts to identify and rehabilitate those most likely to experience hearing threshold change.

Predicting vaginal birth after previous cesarean: Using machine-learning models and a population-based cohort in Sweden.

INTRODUCTION: Predicting a woman's probability of vaginal birth after cesarean could facilitate the antenatal decision-making process. Having a previous vaginal birth strongly predicts vaginal birth after cesarean. Delivery outcome in women with only a cesarean delivery is more unpredictable. Therefore, to better predict vaginal birth in women with only one prior cesarean delivery and no vaginal deliveries would greatly benefit clinical practice and fill a key evidence gap in research. Our aim was to predict vaginal birth in women with one prior cesarean and no vaginal deliveries using machine-learning methods, and compare with a US prediction model and its further developed model for a Swedish setting. MATERIAL AND METHODS: A population-based cohort study with a cohort of 3116 women with only one prior birth, a cesarean, and a subsequent trial of labor during 2008-2014 in the Stockholm-Gotland region, Sweden. Three machine-learning methods (conditional inference tree, conditional random forest and lasso binary regression) were used to predict vaginal birth after cesarean among women with one previous birth. Performance of the new models was compared with two existing models developed by Grobman et al (USA) and Fagerberg et al (Sweden). Our main outcome measures were area under the receiver-operating curve (AUROC), overall accuracy, sensitivity and specificity of prediction of vaginal birth after previous cesarean delivery. RESULTS: The AUROC ranged from 0.61 to 0.69 for all models, sensitivity was above 91% and specificity below 22%. The majority of women with an unplanned repeat cesarean had a predicted probability of vaginal birth after cesarean >60%. CONCLUSIONS: Both classical regression models and machine-learning models had a high sensitivity in predicting vaginal birth after cesarean in women without a previous vaginal delivery. The majority of women with an unplanned repeat cesarean delivery were predicted to succeed with a vaginal birth (ie specificity was low). Additional covariates combined with machine-learning techniques did not outperform classical regression models in this study.

Use of Intrauterine Devices and Risk of Human Immunodeficiency Virus Acquisition Among Insured Women in the United States.

Concerns have been raised about progestin-containing contraceptives and the risk of human immunodeficiency virus (HIV) acquisition. Based on health insurance data from women in the United States with intrauterine device (IUD) insertions during 2011-2018, there was no increased risk of incident HIV diagnosis for levonorgestrel-releasing IUDs versus copper IUDs.

You're From Where, Again? A Critical Assessment of Institutional Diversity in the Society for Epidemiologic Research.

The Society for Epidemiologic Research (SER) has recently taken laudable steps toward increasing diversity, equity, and inclusion within the society, including participation in the annual meeting. In this essay, we argue that there is one critical piece of the diversity and inclusion equation that is, however, overlooked: institution. At the 2019 Annual Meeting, a mere 8 institutions accounted for a disproportionate number of both oral concurrent sessions and symposium speakers. This lack of institutional diversity, unless addressed, will hinder SER's ability to address other aspects of diversity, equity, and inclusion.

Defining maternal obesity in studies of birth outcomes: Comparing ICD-9 codes at delivery and measures on the birth certificate.

BACKGROUND: Using ICD-9 codes underestimates the prevalence of obesity in adults; however, the validity of these codes in studies of pregnancy-related outcomes is not known. OBJECTIVES: To compare classification of maternal obesity based on ICD-9 codes in hospital discharge records versus data from birth certificates in the same women, examine predictors of agreement, and assess how associations between obesity and two birth outcomes differ by source of weight data. METHODS: This population-based study included 2 329 145 California births between 2007 and 2012. We compared data on obesity from childbirth hospital discharge records (ICD-9 codes for obesity) and birth certificates (pre-pregnancy body mass index (BMI) calculated from weight and height) and identified predictors of agreement between the two sources. Logistic regression models assessed whether the two definitions of obesity resulted in different estimates of the associations of obesity with caesarean birth and large-for-gestational age. RESULTS: Overall, 464 754 women (20.0%) had obesity based on their pre-pregnancy BMI while only 100 002 (4.3%) had an obesity-related ICD-9 code. The sensitivity of ICD-9-based obesity was low at 16.2%; however, obesity codes were highly specific at 98.7%, with a negative predictive value of 82.5% and a positive predictive value of 75.2%. Among women with obesity identified by the birth certificate, those with pre-pregnancy and pregnancy-related complications (eg diabetes and hypertension) were more likely to have an obesity-related diagnosis in their delivery hospital discharge record. Using ICD-9 codes overestimated the association of obesity with caesarean birth and newborn large-for-gestational age. CONCLUSIONS: ICD-9 codes in childbirth discharge records captured only one in five women with pre-pregnancy obesity. Sensitivity varied by maternal characteristics and conditions. This misclassification resulted in bias when examining the association of obesity and pregnancy-related outcomes.

The association between longer durations of the latent phase of labor and subsequent perinatal processes and outcomes among midwifery patients.

BACKGROUND/OBJECTIVE: To evaluate the association between the duration of the latent phase of labor and subsequent processes and outcomes. METHODS: Secondary analysis of prospectively collected data among 1,189 women with low-risk pregnancies and spontaneous labor. RESULTS: Longer latent phase duration was associated with labor dystocia (eg, nulliparous ≥ mean [compared with < mean] aOR 3.95 [2.70-5.79]; multiparous ≥ mean [compared with < mean] aOR 5.45 [3.43-8.65]), interventions to ameliorate dystocia, and epidurals to cope or rest (eg, oxytocin augmentation: nulliparous > 80th% [compared with < 80th%] aOR 6.39 [4.04-10.12]; multiparous ≥ 80th% [compared with < 80th%] aOR 6.35 [3.79-10.64]). Longer latent phase duration was also associated with longer active phase and second stage. There were no associations between latent phase duration and risk for cesarean delivery or postpartum hemorrhage in a practice setting with relatively low rates of primary cesarean. Newborns born to multiparous women with latent phase of labor durations at and beyond the 80th% were more frequently admitted to the NICU (≥80th% [compared with < 80th%] aOR 2.7 [1.22-5.84]); however, two-thirds of these NICU admissions were likely for observation only. CONCLUSIONS: Longer duration of the spontaneous latent phase of labor among women with low-risk pregnancies may signal longer total labor processes, leading to an increase in diagnosis of dystocia, interventions to manage dystocia, and epidural use. Apart from multiparous neonatal NICU admission, no other maternal or child morbidity outcomes were elevated with longer duration of the latent phase of labor.

Invited Commentary: The Causal Association Between Obesity and Stillbirth-Strengths and Limitations of the Consecutive-Pregnancies Approach.

There has been a resurgence in analyses of consecutive pregnancies (or similarly, sibling designs) in perinatal and pediatric epidemiology. These approaches have attractive qualities for estimating associations with complex multifactorial exposures like obesity. In an article appearing in this issue of the Journal, Yu et al. (Am J Epidemiol. 2019;188(7):1328-1336) apply a consecutive-pregnancies approach to characterize the risk of stillbirth among women who develop obesity between pregnancies ("incident obesity"). Working within a causal framework and using parametric and nonparametric estimation techniques, the authors find an increase in stillbirth risk associated with incident obesity. Risk differences varied between 0.4 per 1,000 births (95% confidence interval (CI): 0.1, 0.7) and 6.9 per 1,000 births (95% CI: 3.7, 10.0), and risk ratios ranged from 1.12 (95% CI: 1.02, 1.23) to 2.99 (95% CI: 2.19, 4.08). The strengths of this approach include starting from a clearly defined causal estimand and exploring the sensitivity of parameter estimates to model selection. In this commentary, we put these findings in the broader context of research on obesity and birth outcomes and highlight concerns regarding the generalizability of results derived from within-family designs. We conclude that while causal inference is an important goal, in some instances focusing on formulation of a causal question drives results away from broad applicability.

Utility of the 5-Minute Apgar Score as a Research Endpoint.

Although Apgar scores are commonly used as proxy outcomes, little evidence exists in support of the most common cutpoints (<7, <4). We used 2 data sets to explore this issue: one contained planned community births from across the United States (n = 52,877; 2012-2016), and the other contained hospital births from California (n = 428,877; 2010). We treated 5-minute Apgars as clinical "tests," compared against 18 known outcomes; we calculated sensitivity, specificity, positive and negative predictive values, and the area under the receiver operating characteristic curve for each. We used 3 different criteria to determine optimal cutpoints. Results were very consistent across data sets, outcomes, and all subgroups: The cutpoint that maximizes the trade-off between sensitivity and specificity is universally <9. However, extremely low positive predictive values for all outcomes at <9 indicate more misclassification than is acceptable for research. The areas under the receiver operating characteristic curves (which treat Apgars as quasicontinuous) were generally indicative of adequate discrimination between infants destined to experience poor outcomes and those not; comparing median Apgars between groups might be an analytical alternative to dichotomizing. Nonetheless, because Apgar scores are not clearly on any causal pathway of interest, we discourage researchers from using them unless the motivation for doing so is clear.

Increases in Pre-exposure Prophylaxis Use and Decreases in Condom Use: Behavioral Patterns Among HIV-Negative San Francisco Men Who have Sex with Men, 2004-2017.

Using data from the National HIV Behavioral Surveillance of men who have sex with men (MSM), we estimated the prevalence of sexual behaviors among HIV-negative San Francisco MSM between 2004 and 2017. We estimate a recent increase in the 1-year prevalence of pre-exposure prophylaxis (PrEP) use, from 9.8% in 2014 to 44.9% in 2017. Over that same period, we estimate a decrease in the prevalence of consistent condom use, from 18.5 to 9.4%, and an increase in the percent of individuals with multiple condomless anal intercourse partners. We conclude that while risks for HIV infection may be decreasing among San Francisco MSM due, in part, to increases in PrEP use, the population faces increased risks for other sexually transmitted infections (STIs). Because PrEP alone does not protect against other STIs, we strongly recommend that PrEP users use condoms when possible, routinely screen for STIs, and disclose infections with sexual partners.