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Placental abruption, the premature placental separation, confers increased perinatal mortality risk with preterm delivery as an important pathway through which the risk appears mediated. While pregnancies complicated by abruption are often delivered through an obstetrical intervention, many deliver spontaneously. We examined the contributions of clinician-initiated (PTDIND) and spontaneous (PTDSPT) preterm delivery at <37 weeks as competing causal mediators of the abruption-perinatal mortality association. Using the Consortium for Safe Labor (2002-2008) data (n = 203,990; 1.6% with abruption), we applied a potential outcomes-based mediation analysis to decompose the total effect into direct and mediator-specific indirect effects through PTDIND and PTDSPT. Each mediated effect describes the reduction in the counterfactual mortality risk if that preterm delivery subtype was shifted from its distribution under abruption to without abruption. The total effect risk ratio (RR) of abruption on perinatal mortality was 5.4 (95% confidence interval [CI] 4.6, 6.3). The indirect effect RRs for PTDIND and PTDSPT were 1.5 (95% CI: 1.4, 1.6) and 1.5 (95% CI: 1.5, 1.6), respectively; these corresponded to mediated proportions of 25% each. These findings underscore that spontaneous and clinician-initiated preterm deliveries each play essential roles in shaping perinatal mortality risks associated with placental abruption.
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Importance: Patients using assisted reproductive technology (ART) may need additional counseling about the increased risks of placental abruption and preterm delivery. Further investigation into the potential additive risk of ART and placental abruption is needed. Objective: To ascertain the risk of placental abruption in patients who conceived with ART and to evaluate if placental abruption and ART conception are associated with an increased risk of preterm delivery (<37 weeks' gestation) over and above the risks conferred by each factor alone. Design, Setting, and Participants: This cross-sectional study used data from the National Inpatient Sample, which includes data from all-payer hospital inpatient discharges from 48 states across the US. Participants included women aged 15 to 54 years who delivered from 2000 through 2019. Data were analyzed from January 17 to April 18, 2024. Exposures: Pregnancies conceived with ART. Main Outcomes and Measures: Risks of placental abruption and preterm delivery in ART conception compared with spontaneous conceptions. Associations were expressed as odds ratios (ORs) and 95% CIs derived from weighted logistic regression models before and after adjusting for confounders. The relative excess risk due to interaction (RERI) of the risk of preterm delivery based on ART conception and placental abruption was also assessed. Results: Of 78â¯901â¯058 deliveries, the mean (SD) maternal age was 27.9 (6.0) years, and 9 212 117 patients (11.7%) were Black individuals, 14 878 539 (18.9%) were Hispanic individuals, 34 899 594 (44.2%) were White individuals, and 19 910 807 (25.2%) were individuals of other races and ethnicities. Of the total hospital deliveries, 98.2% were singleton pregnancies, 68.8% were vaginal deliveries, and 52.1% were covered by private insurance. The risks of placental abruption among spontaneous and ART conceptions were 11 and 17 per 1000 hospital discharges, respectively. After adjusting for confounders, the adjusted OR (AOR) of placental abruption was 1.42 (95% CI, 1.34-1.51) in ART pregnancies compared with spontaneous conceptions, with increased odds in White women (AOR, 1.42; 95% CI, 1.31-1.53) compared with Black women (AOR, 1.16; 95% CI, 0.93-1.44). The odds of preterm delivery were significantly higher in pregnancies conceived by ART compared with spontaneous conceptions (AOR, 1.46; 95% CI, 1.42-1.51). The risk of preterm delivery increased when patients had both ART conception and placental abruption (RERI, 2.0; 95% CI, 0.5-3.5). Conclusions and Relevance: In this cross-sectional study, patients who conceived using ART and developed placental abruption had a greater risk of preterm delivery compared with spontaneous conception without placental abruption. These findings have implications for counseling patients who seek infertility treatment and obstetrical management of ART pregnancies.
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Descolamento Prematuro da Placenta , Nascimento Prematuro , Técnicas de Reprodução Assistida , Humanos , Feminino , Descolamento Prematuro da Placenta/epidemiologia , Descolamento Prematuro da Placenta/etiologia , Gravidez , Técnicas de Reprodução Assistida/efeitos adversos , Técnicas de Reprodução Assistida/estatística & dados numéricos , Adulto , Estudos Transversais , Nascimento Prematuro/epidemiologia , Adulto Jovem , Adolescente , Pessoa de Meia-Idade , Estados Unidos/epidemiologia , Fatores de RiscoRESUMO
OBJECTIVE: To estimate temporal changes in the prevalence of pre-existing chronic conditions among pregnant women in Sweden and evaluate the extent to which secular changes in maternal age, birth cohorts and obesity are associated with these trends. DESIGN: Population-based cross-sectional study. SETTING: Sweden, 2002-2019. POPULATION: All women (aged 15-49 years) who delivered in Sweden (2002-2019). METHODS: An age-period-cohort analysis was used to evaluate the effects of age, calendar periods, and birth cohorts on the observed temporal trends. MAIN OUTCOME MEASURES: Pre-existing chronic conditions, including 17 disease categories of physical and psychiatric health conditions recorded within 5 years before childbirth, presented as prevalence rates and rate ratios (RRs) with 95% confidence intervals (CIs). Temporal trends were also adjusted for pre-pregnancy body mass index (BMI) and the mother's country of birth. RESULTS: The overall prevalence of at least one pre-existing chronic condition was 8.7% (147 458 of 1 703 731 women). The rates of pre-existing chronic conditions in pregnancy increased threefold between 2002-2006 and 2016-2019 (RR 2.82, 95% CI 2.77-2.87). Rates of psychiatric (RR 3.80, 95% CI 3.71-3.89), circulatory/metabolic (RR 1.62, 95% CI 1.55-1.71), autoimmune/neurological (RR 1.69, 95% CI 1.61-1.78) and other (RR 2.10, 95% CI 1.99-2.22) conditions increased substantially from 2002-2006 to 2016-2019. However, these increasing rates were less pronounced between 2012-2015 and 2016-2019. No birth cohort effect was evident for any of the pre-existing chronic conditions. Adjusting for secular changes in obesity and the mother's country of birth did not affect these associations. CONCLUSIONS: The burden of pre-existing chronic conditions in pregnancy in Sweden increased from 2002 to 2019. This increase may be associated with the improved reporting of diagnoses and advancements in chronic condition treatment among women, potentially enhancing their fecundity.
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Hipertensão , Feminino , Humanos , Gravidez , Doença Crônica , Hipertensão/fisiopatologia , Hipertensão/epidemiologia , Obstetrícia , Complicações Cardiovasculares na Gravidez/fisiopatologia , Complicações Cardiovasculares na Gravidez/epidemiologia , Complicações Cardiovasculares na Gravidez/diagnósticoAssuntos
Ginecologia , Mortalidade Materna , Obstetrícia , Humanos , Estados Unidos/epidemiologia , Feminino , Gravidez , Sociedades Médicas , Vigilância da População/métodos , Morte Materna/prevenção & controle , Complicações na Gravidez/mortalidade , Complicações na Gravidez/prevenção & controle , Obstetra , GinecologistaRESUMO
This article examines the applicability of obstetrical randomized controlled trials (RCTs) in the real-world and proposes a classification of the value of these trials based on their potential for achieving sustainable practices. In the context of this discussion, real-world results pertain to the potential impact of the RCT on sustainable interventions and practices, and its implications for healthcare practice or policy, in the country (or countries) that was conducted. While RCTs are generally regarded as the gold standard of medical evidence, their effectiveness in producing meaningful real-world results depends, among various other factors, on the clarity and specificity of the trial definitions used for diagnosis (characteristics of the study group or enrollment criteria) and treatment (intervention). The definitions used for diagnosis and treatment, especially in pragmatic trials, can influence the likelihood for real-world implementation. By analyzing notable obstetrical RCTs, the authors find that trials with well-defined diagnoses and treatments that can be implemented without specialized expertise are more likely to generate results that are relevant to general practice, indicating higher value. In contrast, RCTs with ambiguous or undefined diagnoses and treatments often lead to variations in practice and produce unreliable real-world outcomes and practices suggesting lower value. Recognizing this variability can offer valuable guidance for the design and evaluation of RCTs in obstetrics.
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Medicina Geral , Obstetrícia , Feminino , Gravidez , Humanos , Ensaios Clínicos Controlados Aleatórios como Assunto , Instalações de Saúde , ProbabilidadeRESUMO
Objective: To evaluate the risk of gestational diabetes mellitus (GDM) in singleton pregnancies conceived using infertility treatment and examine the influence of race and ethnicity as well as prepregnancy body mass index (BMI). Design: Cross-sectional study using the US vital records data of women that delivered singleton births. Setting: United States, 2015-2020. Interventions: Any infertility treatment was divided into two groups: those that used fertility-enhancing drugs, artificial insemination, or intrauterine insemination, and those that used assisted reproductive technology (ART). Main Outcome Measuress: Gestational diabetes mellitus, defined as a diagnosis of diabetes mellitus during pregnancy, includes both diet-controlled GDM and medication-controlled GDM in singleton pregnancies conceived with infertility treatment or spontaneously and delivered between 20- and 44-weeks' gestation. We also examined whether the infertility treatment-GDM association was modified by maternal race and ethnicity as well as prepregnancy BMI. Associations were expressed as a rate ratio (RR) and 95% confidence interval (CI), derived from log-linear models after adjustment for potential confounders. Results: A total of 21,943,384 singleton births were included, with 1.5% (n = 318,086) undergoing infertility treatment. Rates of GDM among women undergoing infertility treatment and those who conceived spontaneously were 11.0% (n = 34,946) and 6.5% (n = 1,398,613), respectively (adjusted RR 1.24, 95% CI 1.23, 1.26). The RRs were adjusted for maternal age, parity, education, race and ethnicity, smoking, BMI, chronic hypertension, and year of delivery. The risk of GDM was modestly increased for those using fertility-enhancing drugs (adjusted RR 1.28, 95% CI 1.27, 1.30) compared with ART (adjusted RR 1.18, 95% CI 1.17, 1.20), and this risk was especially apparent for non-Hispanic White women (adjusted RR 1.29, 95% CI 1.26, 1.31) and Hispanic women (adjusted RR 1.35, 95% CI 1.29, 1.41). The number of women who needed to be exposed to infertility treatment to diagnose one case of GDM was 46. Prepregnancy BMI did not modify the infertility treatment-GDM association overall and within strata of race and ethnicity. These general patterns were stronger after potential corrections for misclassification of infertility treatment and unmeasured confounding. Conclusions: Infertility treatment, among those who received fertility-enhancing drugs, is associated with an increased GDM risk. The persistently higher risk of GDM among women who seek infertility treatment, irrespective of prepregnancy weight classification, deserves attention. Infertility specialists must be vigilant with preconception counseling and ensure that all patients, regardless of race and ethnicity or BMI, are adequately tested for GDM early in pregnancy using a fasting blood glucose level or a traditional 50-g oral glucose tolerance test. Testing may be completed by the infertility specialist or deferred to the primary prenatal care provider at the first prenatal visit.
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Doenças Cardiovasculares , Hipertensão Induzida pela Gravidez , Pré-Eclâmpsia , Gravidez , Feminino , HumanosRESUMO
BACKGROUND: National Vital Statistics System reports show that maternal mortality rates in the United States have nearly doubled, from 17.4 in 2018 to 32.9 per 100,000 live births in 2021. However, these high and rising rates could reflect issues unrelated to obstetrical factors, such as changes in maternal medical conditions or maternal mortality surveillance (eg, due to introduction of the pregnancy checkbox). OBJECTIVE: This study aimed to assess if the high and rising rates of maternal mortality in the United States reflect changes in obstetrical factors, maternal medical conditions, or maternal mortality surveillance. STUDY DESIGN: The study was based on all deaths in the United States from 1999 to 2021. Maternal deaths were identified using the following 2 approaches: (1) per National Vital Statistics System methodology, as deaths in pregnancy or in the postpartum period, including deaths identified solely because of a positive pregnancy checkbox, and (2) under an alternative formulation, as deaths in pregnancy or in the postpartum period, with at least 1 mention of pregnancy among the multiple causes of death on the death certificate. The frequencies of major cause-of-death categories among deaths of female patients aged 15 to 44 years, maternal deaths, deaths due to obstetrical causes (ie, direct obstetrical deaths), and deaths due to maternal medical conditions aggravated by pregnancy or its management (ie, indirect obstetrical deaths) were quantified. RESULTS: Maternal deaths, per National Vital Statistics System methodology, increased by 144% (95% confidence interval, 130-159) from 9.65 in 1999-2002 (n=1550) to 23.6 per 100,000 live births in 2018-2021 (n=3489), with increases occurring among all race and ethnicity groups. Direct obstetrical deaths increased from 8.41 in 1999-2002 to 14.1 per 100,000 live births in 2018-2021, whereas indirect obstetrical deaths increased from 1.24 to 9.41 per 100,000 live births: 38% of direct obstetrical deaths and 87% of indirect obstetrical deaths in 2018-2021 were identified because of a positive pregnancy checkbox. The pregnancy checkbox was associated with increases in less specific and incidental causes of death. For example, maternal deaths with malignant neoplasms listed as a multiple cause of death increased 46-fold from 0.03 in 1999-2002 to 1.42 per 100,000 live births in 2018-2021. Under the alternative formulation, the maternal mortality rate was 10.2 in 1999-2002 and 10.4 per 100,000 live births in 2018-2021; deaths from direct obstetrical causes decreased from 7.05 to 5.82 per 100,000 live births. Deaths due to preeclampsia, eclampsia, postpartum hemorrhage, puerperal sepsis, venous complications, and embolism decreased, whereas deaths due to adherent placenta, renal and unspecified causes, cardiomyopathy, and preexisting hypertension increased. Maternal mortality increased among non-Hispanic White women and decreased among non-Hispanic Black and Hispanic women. However, rates were disproportionately higher among non-Hispanic Black women, with large disparities evident in several causes of death (eg, cardiomyopathy). CONCLUSION: The high and rising rates of maternal mortality in the United States are a consequence of changes in maternal mortality surveillance, with reliance on the pregnancy checkbox leading to an increase in misclassified maternal deaths. Identifying maternal deaths by requiring mention of pregnancy among the multiple causes of death shows lower, stable maternal mortality rates and declines in maternal deaths from direct obstetrical causes.
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Cardiomiopatias , Morte Materna , Gravidez , Feminino , Humanos , Estados Unidos/epidemiologia , Mortalidade Materna , Causas de Morte , Nascido Vivo/epidemiologiaAssuntos
Transtorno do Deficit de Atenção com Hiperatividade , Exposição Materna , Criança , Feminino , Humanos , Inflamação , AtençãoRESUMO
BACKGROUND: Reported rates of maternal mortality in the United States have been staggeringly high and increasing, and cardiovascular disease (CVD) is a chief contributor to such deaths. However, the impact of hypertensive disorders of pregnancy (HDP) on the short-term risk of cardiovascular death is not well understood. OBJECTIVES: To evaluate the association between HDP (chronic hypertension, gestational hypertension, preeclampsia, eclampsia, and superimposed preeclampsia) and pregnancy-associated mortality rates (PMR) from all causes, CVD-related causes both at delivery and within 1 year following delivery. METHODS: We used the Nationwide Readmissions Database (2010-2018) to examine PMRs for females 15-54 years old. International Classification of Disease 9 and 10 diagnosis codes were used to identify pregnancy-associated deaths due to HDP and CVD. Discrete-time Cox proportional hazards regression models were used to calculate adjusted hazard ratios (HR) and 95% confidence intervals (CI) for mortality at delivery (0 days) and at <30, <60, <90, <180, and <365 days after delivery in relation to HDP. RESULTS: Of 33,417,736 hospital deliveries, the rate of HDP was 11.0% (n = 3,688,967), and the PMR from CVD was 6.4 per 100,000 delivery hospitalisations (n = 2141). Compared with normotensive patients, HRs for CVD-related PMRs increased with HDP severity, reaching over 58-fold for eclampsia patients. HRs were higher for stroke-related (1.2 to 170.9) than heart disease (HD)-related (0.99 to 39.8) mortality across all HDPs. Except for gestational hypertension, the increased risks of CVD mortality were evident at delivery and persisted 1 year postpartum for all HDPs. CONCLUSIONS: HDPs are strong risk factors for pregnancy-associated mortality due to CVD at delivery and within 1 year postpartum; the risks are stronger for stroke than HD-related PMR. While absolute PMRs are low, this study supports the importance of extending postpartum care beyond the traditional 42-day postpartum visit for people whose pregnancies are complicated by hypertension.
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Doenças Cardiovasculares , Eclampsia , Hipertensão Induzida pela Gravidez , Pré-Eclâmpsia , Acidente Vascular Cerebral , Gravidez , Feminino , Humanos , Adolescente , Adulto Jovem , Adulto , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Cardiovascular disease is a major cause of maternal mortality, but the extent to which infertility treatment is implicated in heart disease remains unclear. OBJECTIVE: To evaluate the association between infertility treatment and postpartum heart disease. METHODS: We designed a retrospective cohort study of patients who delivered in the United States between 2010 and 2018. The primary outcome was hospitalization within 12-month post-delivery due to heart disease (including ischemic heart disease, atherosclerotic heart disease, cardiomyopathy, hypertensive disease, heart failure, and cardiac dysrhythmias). We estimated the rate difference (RD) of hospitalizations among patients who conceived with infertility treatment and those who conceived spontaneously. Associations were expressed as hazard ratios (HRs) and 95% confidence intervals (CIs), derived from Cox proportional hazards regression after adjustment for potential confounders. RESULTS: Infertility treatment was recorded in 0.9% (n = 287,813) of 31,339,991 deliveries. Rates of heart disease hospitalizations with infertility treatment and with spontaneous conception were 550 and 355 per 100,000, respectively (RD 195, 95% CI: 143-247; adjusted HR 1.99, 95% CI: 1.80-2.20). The most important increase in risk was observed for hypertensive disease (adjusted HR 2.16, 95% CI: 1.92-2.42). This increased risk was apparent as early as 30-day post-delivery (HR 1.61, 95% CI: 1.39-1.86), with progressively increasing risk up to a year. CONCLUSIONS: Although the absolute risk of postpartum heart disease hospitalization is low, infertility treatment is associated with an increased risk, especially for hypertensive disease. These findings highlight the importance of timely postpartum follow-ups in patients who received infertility treatment.
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Insuficiência Cardíaca , Hipertensão , Infertilidade , Feminino , Humanos , Estados Unidos/epidemiologia , Estudos Retrospectivos , Hospitalização , Período Pós-Parto , Insuficiência Cardíaca/epidemiologiaRESUMO
BACKGROUND: Although smoking cigarettes has been shown to have a protective effect on preeclampsia, quitting smoking also results in weight gain. Weight gain leading to an obese body mass index is a risk factor for hypertensive disorders of pregnancy (HDP). METHODS: The objective of this study was to explore the relationship between smoking status, body mass index, and gestational weight gain on the risk of HDP. A cross-sectional analysis was performed utilizing US birth certificate data. We examined HDP risks in relation to maternal smoking, body mass index, and gestational weight gain. Associations were expressed as rate ratios with 95% CIs and adjusted for potential confounders. Clinically important outcomes of smoking throughout pregnancy were also evaluated. RESULTS: Of the 22 191 568 women studied, HDP rates among nonsmokers, those who quit smoking, and persistent smokers were 6.8%, 8.6%, and 7.0%, respectively. The rate ratio of HDP was higher for women who quit smoking, especially evident among those with excessive gestational weight gain. Corrections for exposure misclassification and unmeasured confounding strengthened the associations among women who quit smoking. There was an almost 6-fold increase in the rate of stillbirth for persistent smokers (2.3%) compared with those who quit smoking (0.4%) and nonsmokers (0.4%). CONCLUSIONS: Women who quit smoking during pregnancy were more likely to gain excessive weight and develop HDP. Although quitting smoking during pregnancy may be associated with an increase in the risk of HDP, it is also associated with a reduced risk of stillbirth. Pregnant women counseled to quit smoking should also receive counseling on nutrition and exercise to prevent excessive gestational weight gain.
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Índice de Massa Corporal , Ganho de Peso na Gestação , Hipertensão Induzida pela Gravidez , Fumar , Humanos , Feminino , Gravidez , Hipertensão Induzida pela Gravidez/epidemiologia , Adulto , Estudos Transversais , Fumar/efeitos adversos , Fumar/epidemiologia , Fatores de Risco , Estados Unidos/epidemiologia , Abandono do Hábito de Fumar/estatística & dados numéricos , Adulto Jovem , Medição de Risco/métodosRESUMO
BACKGROUND: Pre-existing health conditions increase the risk of obstetric complications during pregnancy and birth. However, the prevalence and recent changes in the frequency of pre-existing health conditions in the childbearing population remain unknown. OBJECTIVES: To estimate the temporal changes in the prevalence of pre-existing health conditions among pregnant women in British Columbia, Canada. METHODS: We carried out a population-based cross-sectional study of 825,203 deliveries in BC between 2000 and 2019 and examined 17 categories of physical and psychiatric health conditions recorded within 5 years before childbirth. We also undertook age-period-cohort analyses to evaluate temporal changes in pre-existing health conditions. RESULTS: The prevalence of any pre-existing health condition was 26.2% (n = 216,214) with overall trends remaining stable during the study period. Between 2000 and 2019, the prevalence rates of anxiety (5.6%-9.6%), bipolar (1.6%-3.4%), psychosis (0.7%-0.8%), and eating disorders (0.2%-0.3%) increased. The prevalence of hypertension increased sharply from 0.06% in 2000 to 0.3% in 2019. Diabetes mellitus and stroke rates increased, as did the prevalence of systemic lupus, multiple sclerosis, and chronic kidney disease. Advanced maternal age was strongly associated with both psychiatric and circulatory/metabolic conditions. A strong birth cohort effect was evident, with rates of psychiatric conditions increasing among women born after 1985. CONCLUSIONS: In British Columbia, Canada, 1 in 4 mothers had a pre-existing health condition 5 years prior to pregnancy. These findings underscore the need for multi-disciplinary care for women with pre-existing health conditions to improve maternal, foetal, and infant health.
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Complicações na Gravidez , Humanos , Feminino , Colúmbia Britânica/epidemiologia , Gravidez , Adulto , Estudos Transversais , Complicações na Gravidez/epidemiologia , Prevalência , Adulto Jovem , Transtornos Mentais/epidemiologia , Adolescente , Nível de SaúdeRESUMO
BACKGROUND: Obstetrical complications impact the health of mothers and offspring along the life course, resulting in an increased burden of chronic diseases. One specific complication is abruption, a life-threatening condition with consequences for cardiovascular health that remains poorly studied. OBJECTIVES: To describe the design and data linkage algorithms for the Placental Abruption and Cardiovascular Event Risk (PACER) cohort. POPULATION: All subjects who delivered in New Jersey, USA, between 1993 and 2020. DESIGN: Retrospective, population-based, birth cohort study. METHODS: We linked the vital records data of foetal deaths and live births to delivery and all subsequent hospitalisations along the life course for birthing persons and newborns. The linkage was based on a probabilistic record-matching algorithm. PRELIMINARY RESULTS: Over the 28 years of follow-up, we identified 1,877,824 birthing persons with 3,093,241 deliveries (1.1%, n = 33,058 abruption prevalence). The linkage rates for live births-hospitalisations and foetal deaths-hospitalisations were 92.4% (n = 2,842,012) and 70.7% (n = 13,796), respectively, for the maternal cohort. The corresponding linkage rate for the live births-hospitalisations for the offspring cohort was 70.3% (n = 2,160,736). The median (interquartile range) follow-up for the maternal and offspring cohorts was 15.4 (8.1, 22.4) and 14.4 (7.4, 21.0) years, respectively. We will undertake multiple imputations for missing data and develop inverse probability weights to account for selection bias owing to unlinked records. CONCLUSIONS: Pregnancy offers a unique window to study chronic diseases along the life course and efforts to identify the aetiology of abruption may provide important insights into the causes of future CVD. This project presents an unprecedented opportunity to understand how abruption may predispose women and their offspring to develop CVD complications and chronic conditions later in life.
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Descolamento Prematuro da Placenta , Complicações Cardiovasculares na Gravidez , Gravidez , Feminino , Recém-Nascido , Humanos , Descolamento Prematuro da Placenta/epidemiologia , Estudos de Coortes , Estudos Retrospectivos , Placenta , Fatores de Risco , Complicações Cardiovasculares na Gravidez/epidemiologia , Morte Fetal , Doença CrônicaRESUMO
OBJECTIVE: There is uncertainty regarding the effect of the COVID-19 pandemic on population rates of stillbirth. We quantified pandemic-associated changes in stillbirth rates in Canada and the United States. METHODS: We carried out a retrospective study that included all live births and stillbirths in Canada and the United States from 2015 to 2020. The primary analysis was based on all stillbirths and live births at ≥20 weeks gestation. Stillbirth rates were analyzed by month, with March 2020 considered to be the month of pandemic onset. Interrupted time series analyses were used to determine pandemic effects. RESULTS: The study population included 18 475 stillbirths and 2 244 240 live births in Canada and 134 883 stillbirths and 22 963 356 live births in the United States (8.2 and 5.8 stillbirths per 1000 total births, respectively). In Canada, pandemic onset was associated with an increase in stillbirths at ≥20 weeks gestation of 1.01 (95% confidence interval [CI] 0.56-1.46) per 1000 total births and an increase in stillbirths at ≥28 weeks gestation of 0.35 (95% CI 0.16-0.54) per 1000 total births. In the United States, pandemic onset was associated with an increase in stillbirths at ≥20 weeks gestation of 0.48 (95% CI 0.22-0.75) per 1000 total births and an increase in stillbirths at ≥28 weeks gestation of 0.22 (95% CI 0.12-0.32) per 1000 total births. The increase in stillbirths at pandemic onset returned to pre-pandemic levels in subsequent months. CONCLUSION: The COVID-19 pandemic's onset was associated with a transitory increase in stillbirth rates in Canada and the United States.