Cardiovascular severe maternal morbidity in pregnant and postpartum women: development and internal validation of risk prediction models.

OBJECTIVES: To develop and internally validate risk prediction models identifying women at risk for cardiovascular severe maternal morbidity (CSMM). DESIGN: A retrospective cohort study. SETTING: An obstetric teaching hospital between 2007 and 2017. POPULATION: A total of 89 681 delivery hospitalisations. METHODS: We created and evaluated two models, one predicting CSMM at delivery (delivery model) and the other predicting CSMM postpartum following discharge from delivery hospitalisation (postpartum CSMM). We assessed model discrimination and calibration and used bootstrapping for internal validation. MAIN OUTCOME MEASURES: Cardiovascular severe maternal morbidity comprised the following confirmed conditions: pulmonary oedema/acute heart failure, myocardial infarction, aneurysm, cardiac arrest/ventricular fibrillation, heart failure/arrest during surgery or procedure, cerebrovascular disorders, cardiogenic shock, conversion of cardiac rhythm and difficult-to-control severe hypertension. RESULTS: The delivery model contained 11 variables and 3 interaction terms. The strongest predictors were gestational hypertension, chronic hypertension, multiple gestation, cardiac lesions or valvular heart disease, maternal age ≥40 years and history of poor pregnancy outcome. The postpartum model comprised eight variables. The strongest predictors were severe pre-eclampsia, non-Hispanic Black race/ethnicity, chronic hypertension, gestational hypertension, non-severe pre-eclampsia and maternal age ≥40 years at delivery. The delivery and postpartum models had an area under the receiver operating characteristic curve of 0.87 (95% CI 0.85-0.89) and 0.85 (95% CI 0.80-0.90), respectively. Both models were adequately calibrated and performed well on internal validation. CONCLUSIONS: These tools may help providers to identify women at highest risk of CSMM and enable future prevention measures. TWEETABLE ABSTRACT: Risk assessment tools for cardiovascular severe maternal morbidity were developed and internally validated.

Maternal influenza and birth outcomes: systematic review of comparative studies.

BACKGROUND: Although pregnant women are considered at high risk for severe influenza disease, comparative studies of maternal influenza and birth outcomes have not been comprehensively summarised. OBJECTIVE: To review comparative studies evaluating maternal influenza disease and birth outcomes. SEARCH STRATEGY: We searched bibliographic databases from inception to December 2014. SELECTION CRITERIA: Studies of preterm birth, small-for-gestational-age (SGA) birth or fetal death, comparing women with and without clinical influenza illness or laboratory-confirmed influenza infection during pregnancy. DATA COLLECTION AND ANALYSIS: Two reviewers independently abstracted data and assessed study quality. MAIN RESULTS: Heterogeneity across 16 studies reporting preterm birth precluded meta-analysis. In a subgroup of the highest-quality studies, two reported significantly increased preterm birth (risk ratios (RR) from 2.4 to 4.0) following severe 2009 pandemic H1N1 (pH1N1) influenza illness, whereas those assessing mild-to-moderate pH1N1 or seasonal influenza found no association. Five studies of SGA birth showed no discernible patterns with respect to influenza disease severity (pooled odds ratio 1.24; 95% CI 0.96-1.59). Two fetal death studies were of sufficient quality and size to permit meaningful interpretation. Both reported an increased risk of fetal death following maternal pH1N1 disease (RR 1.9 for mild-to-moderate disease and 4.2 for severe disease). CONCLUSIONS: Comparative studies of preterm birth, SGA birth and fetal death following maternal influenza disease are limited in number and quality. An association between severe pH1N1 disease and preterm birth and fetal death was reported by several studies; however, these limited data do not permit firm conclusions on the magnitude of any association. TWEETABLE ABSTRACT: Comparative studies are limited in quality but suggest severe pandemic H1N1 influenza increases preterm birth.

The effect of labour induction on the risk of caesarean delivery: using propensity scores to control confounding by indication.

OBJECTIVE: To use propensity score methods to control for confounding by indication in the association between labour induction and caesarean delivery. DESIGN: Cross-sectional analysis of administrative hospital discharge data supplemented by medical record information. SETTING: Fourteen US member hospitals of the National Perinatal Information Center. SAMPLE: A cohort of 166 559 singleton liveborn deliveries in the period 2007-2012. METHODS: We used propensity scores (PSs) to balance 83 covariates between induced and non-induced women, and compared estimates with traditional covariate adjustment. We estimated PSs for labour induction versus expectant management of pregnancy each week from 34 to 42 weeks of gestation. We estimated risk ratios (RRs) for the association between labour induction and primary caesarean delivery from models with no adjustment, traditional adjustment of five covariates, matched PS, and adjustment for continuous PS. MAIN OUTCOME MEASURE: Caesarean delivery in current or subsequent week of gestation. RESULTS: In crude models labour induction increased the risk of caesarean delivery in all weeks (RR 1.06-1.52), excepting 39 weeks of gestation (RR 0.89). After matching on PS, the analysis showed a significantly decreased risk of caesarean delivery with labour induction during weeks 35-39 (RR 0.77-0.92), and a significantly elevated risk at weeks 40 (RR 1.22) and 41 (RR 1.39). Traditional covariate and PS adjustment resulted in RRs between those from crude and PS-matched models. CONCLUSIONS: There is evidence of considerable confounding by indication in the association of labour induction and caesarean delivery, particularly for preterm deliveries. Using PS methods, we found a reduced risk of caesarean delivery with labour induction before 40 weeks of gestation, and an elevated risk for weeks 40-42. TWEETABLE ABSTRACT: With confounding adjustment, labour induction does not increase the risk of caesarean at 34-39 weeks of gestation.

Ethnic enclaves and gestational diabetes among immigrant women in New York City.

Previous research has shown that immigrants living in their own ethnic enclave are at decreased risk of poor health outcomes, but this question has not been studied in relation to gestational diabetes, an important early marker of lifecourse cardiovascular health. We ascertained gestational diabetes, census tract of residence, and individual-level covariates for Sub-Saharan African, Chinese, South Central Asian, Non-Hispanic Caribbean, Dominican, Puerto Rican, Mexican, and Central and South American migrant women using linked birth-hospital discharge data for 89,703 singleton live births in New York City for the years 2001-2002. Using 2000 census data, for each immigrant group we defined a given census tract as part of an ethnic enclave based on the population distribution for the corresponding ethnic group. We estimated odds ratios for associations between living in an ethnic enclave and risk of gestational diabetes adjusted for neighborhood deprivation, percent commercial space, education, age, parity, and insurance status, using multilevel logistic regression. Overall, we found no effect of ethnic enclave residence on gestational diabetes in most immigrant groups. Among South Central Asian and Mexican women, living in a residential ethnic enclave was associated with an increased odds of gestational diabetes. Several explanations are proposed for these findings. Mechanisms explaining an increased risk of gestational diabetes in South Central Asian and Mexican ethnic enclaves should be examined.

Disparities in cesarean delivery by ethnicity and nativity in New York city.

Our objective was to examine differences in risk of cesarean delivery among diverse ethnic groups in New York City. Using cross-sectional New York City birth and hospitalization data from 1995 to 2003 (n = 961,381) we estimated risk ratios for ethnic groups relative to non-Hispanic whites and immigrant women relative to US-born women. Adjusting for insurance, pre-pregnancy weight, maternal age, education, parity, birthweight, gestational age, year, medical complications, and pregnancy complications, all ethnic groups except East Asian women were at an increased risk of cesarean delivery, with the highest risk among Hispanic Caribbean women [adjusted risk ratio (aRR) = 1.27, 95 % CI (confidence interval) = 1.24, 1.30] and African American women (aRR = 1.20, 95 % CI = 1.17, 1.23). Among Hispanic groups, immigrant status further increased adjusted risk of cesarean delivery; adjusted risk ratios for foreign-born women compared to US-born women of the same ethnic group were 1.27 for Mexican women (95 % CI = 1.05, 1.53), 1.23 for Hispanic Caribbean women (95 % CI = 1.20, 1.27), and 1.12 for Central/South American women (95 % CI = 1.04, 1.21). Similar patterns were found in subgroup analyses of low-risk women (term delivery and no pregnancy or medical complications) and primiparous women. We found evidence of disparities by ethnicity and nativity in cesarean delivery rates after adjusting for multiple risk factors. Efforts to reduce rates of cesarean delivery should address these disparities. Future research should explore potential explanations including hospital environment, provider bias, and patient preference.

Changes in delivery methods at specialty care hospitals in the United States between 2006 and 2010.

OBJECTIVE: Given the increasing rates of labor induction and cesarean delivery, and efforts to reduce early term births, we examined recent trends in methods and timing of delivery. STUDY DESIGN: We identified delivery methods and medical indications for delivery from administrative hospital discharge data for 231 691 deliveries in 2006 and 213 710 deliveries in 2010 from 47 specialty care member hospitals of the National Perinatal Information Center/Quality Analytic Services. In a subset of 17 hospitals, we examined trends by gestational age. RESULT: From 2006 to 2010, there was an 11% increase in labor induction and a 6% increase in cesarean delivery, largely due to repeat cesareans. There was a 4 per 100 reduction in early term births (37 to 38 weeks), mostly due to a decline in non-medically indicated interventional deliveries. CONCLUSION: We report a shift in deliveries at 38 weeks, which we believe may be attributed to efforts to actively limit non-medically indicated early term deliveries.

Physical activity and maternal-fetal circulation measured by Doppler ultrasound.

OBJECTIVE: To examine the association of physical activity on maternal-fetal circulation measured by uterine and umbilical artery Doppler flow velocimetry waveforms. STUDY DESIGN: Participants included 781 pregnant women with Doppler ultrasounds of the uterine and umbilical artery and who self-reported past week physical activity. Linear and generalized estimating equation regression models were used to examine these associations. RESULT: Moderate-to-vigorous total and recreational activity were associated with higher uterine artery pulsatility index (PI) and an increased risk of uterine artery notching as compared with reporting no total or recreational physical activity, respectively. Moderate-to-vigorous work activity was associated with lower uterine artery PI and a reduced risk of uterine artery notching as compared with no work activity. No associations were identified with the umbilical circulation measured by the resistance index. CONCLUSION: In this epidemiologic study, recreational and work activity were associated with opposite effects on uterine artery PI and uterine artery notching, although associations were modest in magnitude.

Ethnic differences in the association between gestational diabetes and pregnancy outcome.

The purpose of the study was to examine ethnic variation in the impact of Gestational Diabetes Mellitus (GDM) on birth outcome. The authors examined the association between GDM and pregnancy-induced hypertension, macrosomia, primary Cesarean delivery, and preterm birth, using New York City Birth Certificate data from 2001-2006. Logistic regression was used to evaluate the crude and adjusted odds ratios of GDM with each adverse perinatal event, stratified by ethnicity. GDM was associated with increased risk of adverse perinatal events among all ethnic groups, with modest variation by ethnicity. Across ethnic groups, adjusted odds ratios comparing women with and without GDM ranged from 1.4-2.9 for pregnancy-induced hypertension, 1.0-2.2 for macrosomia, 1.1-1.8 for primary Cesarean delivery, and 1.3-1.8 for preterm birth. Overall, Caribbean, Sub-Saharan African, and African American women tended to show a larger relative impact of GDM, while North African, South Central Asian, and Chinese women showed a comparatively smaller impact of GDM. Although some ethnic variation was seen, differences in effect size were not large enough to support ethnic-specific thresholds for GDM diagnosis and treatment.

First-trimester bleeding characteristics associate with increased risk of preterm birth: data from a prospective pregnancy cohort.

BACKGROUND: Prior evidence linking first-trimester bleeding with preterm birth (PTB, <37 weeks gestation) risk has been inconsistent and may be biased by subject selection and/or incomplete documentation of bleeding episodes for all participants. Prior studies have not carefully examined the role of bleeding characteristics in PTB risk. In the present study, we estimate the association between first-trimester bleeding and PTB in a non-clinical prospective cohort and test whether bleeding characteristics better predict risk. METHODS: Women were enrolled in Right from the Start (2000-2009), a prospective pregnancy cohort. Data about bleeding and bleeding characteristics were examined with logistic regression to assess association with PTB. RESULTS: Among 3978 pregnancies 344 were PTB and 3634 term. Bleeding was reported by 986 (26%) participants. After screening candidate confounders, only multiple gestations remained in the model. Bleeding associated with PTB [odds ratio (OR)(adjusted) = 1.40, 95% confidence interval (CI) 1.09-1.80]. Risk did not vary by race/ethnicity. Compared with non-bleeders, PTB risk was higher for bleeding with red color (OR(adjusted) = 1.92, 95% CI, 1.32-2.82), for heavy episodes (OR(adjusted) = 2.40, 95% CI 1.18-4.88) and long duration (OR(adjusted) = 1.67, 95% CI 1.17-2.38). CONCLUSIONS: Bleeding associated with PTB was not confounded by common risk factors for bleeding or PTB. PTB risk was greatest for women with heavy bleeding episodes with long duration and red color and would suggest that combining women with different bleeding characteristics may affect the accuracy of risk assessment. These data suggest a candidate etiologic pathway for PTB and warrant further investigation of the biologic mechanisms.

Registration of observational studies does not enhance validity.

Mandatory registration of observational studies has been proposed to enhance quality of published research and reduce selective publication of positive findings. Enhanced communication of study plans would be welcome, but the alleged benefits to research quality are illusory. In particular, prespecification of hypotheses has no independent effect on data quality or the likelihood that hypotheses are correct. Registration of studies and hypotheses is likely to be misinterpreted as an independent determinant of validity.

Maternal education and adverse birth outcomes among immigrant women to the United States from Eastern Europe: a test of the healthy migrant hypothesis.

Immigrant women to the U.S. often have more favorable birth outcomes than their native-born counterparts, including lower rates of preterm birth and low birth weight, a phenomenon commonly attributed to a healthy migrant effect. However, this effect varies by ethnicity and country of origin. No previous study has examined birth outcomes among immigrants from the post-Communist countries of Eastern Europe, a group which includes both economic migrants and conflict refugees. Using data on 253,363 singletons births from New York City during 1995-2003 we examined the risk of preterm birth (PTB) (<37 weeks) or delivering a term small-for-gestational-age (SGA) infant among immigrants from Russia and Ukraine (RU), Poland, and former Yugoslavia Republics (FYR) relative to US-born non-Hispanic whites (NHW). Women in all three Eastern European groups had significantly later entry into prenatal care, were more likely to be Medicaid recipients, and had lower educational attainment than US-born NHW. In binomial regression analyses adjusting for age, education, parity, and pre-pregnancy weight, women from RU and FYR had lower risk of PTB than US-born NHW, whereas women from Poland had similar risk. Lower SGA risk was found among women from Poland and FYR, but not RU. When stratified by education, women with <12 years of education from all Eastern European groups had a reduced risk of PTB relative to US-born NHW. An educational gradient in PTB and SGA risk was less pronounced in all Eastern European groups compared to US-born NHW. The healthy migrant effect is present among immigrants from Eastern Europe to the U.S., especially among women with less education and those from the former Yugoslavia, a group that included many conflict refugees.

Neighborhood deprivation and adverse birth outcomes among diverse ethnic groups.

PURPOSE: Living in a socioeconomically deprived neighborhood has been associated with an increased risk of adverse birth outcomes. However, variation in the effect of neighborhood deprivation among diverse ethnic groups has not been studied. METHODS: Using linked hospital discharge and birth data for 517,994 singleton live births in New York City from 1998 through 2002, we examined the association between neighborhood deprivation, preterm birth (PTB), and term low birthweight (TLBW) (>or=37 weeks and <2500g). Adjusted odds ratios (aORs) for PTB (<32 and 33-36 weeks) and TLBW were estimated using logistic regression. RESULTS: The aOR for PTB of less than 32 weeks for the highest quartile of deprivation compared to the lowest was 1.24 (95% confidence limit [CL] = 1.13, 1.36), for PTB 33-36 weeks was 1.06 (95% CL = 1.01, 1.11), and for TLBW was 1.19 (95% CL = 1.11, 1.27). Measures of association varied by ethnicity; aORs of the greatest magnitude for PTB were found among Hispanic Caribbean women (PTB < 32 weeks: aOR = 1.63, 95% CL = 1.27, 2.10; PTB 33-36 weeks: aOR = 1.32, 95% CL = 1.02, 1.70), and for TLBW among African women (aOR = 1.47, 95% CL = 1.02, 2.13). CONCLUSIONS: The mechanisms linking neighborhood deprivation to adverse birth outcomes may differ depending on individual ethnicity and/or cultural context and should be investigated in future research.

Ethnicity and gestational diabetes in New York City, 1995-2003.

OBJECTIVE: To characterise the patterns of occurrence of gestational diabetes among a wide range of ethnic groups that reside in New York City. DESIGN: Birth records and hospital discharge data were linked to more accurately assess the risk of gestational diabetes by ethnicity, compare risk in US-born to foreign-born women, and assess time trends. SETTING: New York City. POPULATION: All singleton live births occurring between 1995 and 2003. METHODS: Multivariable binomial regression analysis of ethnicity and gestational diabetes, yielding adjusted risk ratios with non-Hispanic white women as the referent. MAIN OUTCOME MEASURE: Diagnosis of gestational diabetes on birth certificate or in hospital discharge. RESULTS: Adjusted relative risks (aRRs) were modestly elevated for African-Americans and sub-Saharan Africans and somewhat higher (<2.0) for non-Hispanic Caribbeans, Hispanic Caribbeans, Central Americans, and South Americans. The aRR was 4.7 (95% CI = 4.6-4.9) for South Central Asians (with an absolute gestational diabetes risk of 14.3%), 2.8 (95% CI = 2.7-3.0) among South-East Asian and Pacific Islanders, and 2.3 (95% CI = 2.2-2.4) among East Asians. Among South Central Asians, the greatest risks were found for women from Bangladesh (aRR = 7.1, 95% CI = 6.8-7.3). Foreign-born women consistently had higher risk than US-born women. Risk for gestational diabetes increased over time among South Central Asians, some Hispanic groups, and African-Americans. CONCLUSIONS: Risk of gestational diabetes appears to vary markedly among ethnic groups, subject to potential artefacts associated with screening and diagnosis. These differences would have direct implications for health care and may suggest aetiologic hypotheses.

Stress and placental resistance measured by Doppler ultrasound in early and mid-pregnancy.

OBJECTIVES: To examine the association between self reports and biomarkers of stress and placental resistance (measured by Doppler ultrasound of the uterine and umbilical arteries), to determine if restriction of blood flow to the placenta is a mechanism by which stress might affect health during pregnancy. METHODS: Eight hundred and seventy-two women had ultrasound examinations of the uterine artery at 15-19 weeks' gestation and the uterine and umbilical arteries at 24-29 weeks, and resistance and pulsatility indices were calculated. Psychosocial stress was measured by telephone interview and self-administered questionnaire using several validated tools twice during the pregnancy. Cortisol and corticotropin-releasing hormone (CRH) were measured twice during the pregnancy. Linear and hierarchical models were used to examine the relationships among reported stress, stress hormones and placental Doppler indices. RESULTS: The umbilical artery resistance index was higher in younger women, those with less education, those who were single and those who smoked. The uterine artery pulsatility index was higher in women with pre-eclampsia, those living alone, those with high body mass index, and those who gained the least weight during pregnancy. A higher CRH level was associated with small increases in uterine artery pulsatility and umbilical artery resistance indices. Psychosocial measures of stress were not consistently associated with higher placental resistance. CONCLUSIONS: Increased CRH levels may be associated with increased placental resistance. Otherwise, these findings do not support the hypothesis that restriction of blood flow to the fetus is a major mechanism by which stress affects infant health.

Psychological and biological markers of stress and bacterial vaginosis in pregnant women.

OBJECTIVES: To determine whether stress is associated with risk of bacterial vaginosis (BV) in pregnant women. DESIGN: Prospective cohort study. SETTING: The prenatal care clinics at the University of North Carolina. The residents' clinic sees mostly government-insured and uninsured women, and the physicians' clinic sees mostly those with private health insurance. POPULATION: A total of 897 women gave samples for BV analysis. Study participants were 22% African-American, 68% white; 24% unmarried and 44% nulliparous. More than half had completed college. METHODS: Women completed two questionnaires and two interviews reporting stress and psychological aspects of their lives. Measurement scales included the Sarason life events questionnaire, the Cohen perceived stress scale, Spielberger state-trait anxiety, the John Henryism coping style and the Medical Outcomes Study social support inventory. Two stress hormones, corticotrophin-releasing hormone and cortisol, were also measured. MAIN OUTCOME MEASURES: BV at 15-19 and 24-29 weeks of gestation was diagnosed by Gram's stain. RESULTS: Women in the highest quartile of stress measures, particularly state anxiety (OR=2.0, 95% CI 1.2-3.3), perceived stress (OR=2.4, 95% CI 1.5-3.9) and total life events (OR=2.0, 95% CI 1.3-3.2), had the highest risk of BV. Adjustment for confounders, especially age, race, and income, reduced these associations (state anxiety: OR=1.3, 95% CI 0.7-2.4; perceived stress: OR=1.4, 95% CI 0.8-2.5; total life events: OR=1.3, 95% CI 0.7-2.4). No clear pattern of association was seen between stress hormones and BV. CONCLUSIONS: Few associations between stress and BV were seen after adjustment for confounders.

Relation between ambient air quality and selected birth defects, seven county study, Texas, 1997-2000.

A population-based case-control study investigated the association between maternal exposure to air pollutants, carbon monoxide, nitrogen dioxide, ozone, sulfur dioxide, and particulate matter <10 microm in aerodynamic diameter during weeks 3-8 of pregnancy and the risk of selected cardiac birth defects and oral clefts in livebirths and fetal deaths between 1997 and 2000 in seven Texas counties. Controls were frequency matched to cases on year of birth, vital status, and maternal county of residence at delivery. Stationary monitoring data were used to estimate air pollution exposure. Logistic regression models adjusted for covariates available in the vital record. When the highest quartile of exposure was compared with the lowest, the authors observed positive associations between carbon monoxide and tetralogy of Fallot (odds ratio = 2.04, 95% confidence interval: 1.26, 3.29), particulate matter <10 microm in aerodynamic diameter and isolated atrial septal defects (odds ratio = 2.27, 95% confidence interval: 1.43, 3.60), and sulfur dioxide and isolated ventricular septal defects (odds ratio = 2.16, 95% confidence interval: 1.51, 3.09). There were inverse associations between carbon monoxide and isolated atrial septal defects and between ozone and isolated ventricular septal defects. Evidence that air pollution exposure influences the risk of oral clefts was limited. Suggestive results support a previously reported finding of an association between ozone exposure and pulmonary artery and valve defects.

Pesticide use and menstrual cycle characteristics among premenopausal women in the Agricultural Health Study.

Menstrual cycle characteristics may have implications for women's fecundability and risk of hormonally related diseases. Certain pesticides disrupt the estrous cycle in animals. The authors investigated the cross-sectional association between pesticide use and menstrual function among 3,103 women living on farms in Iowa and North Carolina. Women were aged 21-40 years, premenopausal, not pregnant or breastfeeding, and not taking oral contraceptives. At study enrollment (1993-1997), women completed two self-administered questionnaires on pesticide use and reproductive health. Exposures of interest were lifetime use of any pesticide and hormonally active pesticides. Menstrual cycle characteristics of interest included cycle length, missed periods, and intermenstrual bleeding. The authors used generalized estimating equations to assess the association between pesticide use and menstrual cycle characteristics, controlling for age, body mass index, and current smoking status. Women who used pesticides experienced longer menstrual cycles and increased odds of missed periods (odds ratio = 1.5, 95% confidence interval: 1.2, 1.9) compared with women who never used pesticides. Women who used probable hormonally active pesticides had a 60-100% increased odds of experiencing long cycles, missed periods, and intermenstrual bleeding compared with women who had never used pesticides. Associations remained after control for occupational physical activity.

Risk factors for preterm birth in Vietnam.

OBJECTIVE: To identify the risk of preterm birth and possible determinants among women in Hanoi, Vietnam. METHOD: Prospective cohort study of 1709 women with singleton live births at Hanoi Obstetrics and Gynecology Hospital, Hanoi, Vietnam, June-October 2002. Logistic regression analysis was used to examine predictors of preterm birth (<37 weeks' gestation). RESULT: The risk of preterm birth was 11.8%. Physically demanding work during pregnancy, two or more prior spontaneous abortions, history of preterm birth, vaginal bleeding, inadequate prenatal care during the first 20 weeks of gestation, and history of intrauterine device use with removal less than 12 months before the current pregnancy were associated with increased risk of preterm birth (adjusted odds ratios between 1.8 and 2.6). CONCLUSION: Preterm birth is relatively frequent in this population. Beyond established risk factors, these data implicated agricultural work and physical work demands with preterm birth, as well as history of recent IUD use.