Vital Status Ascertainment for a Historic Diverse Cohort of U.S. Women

Cesarean delivery, labor duration, and mothers' mortality risk over 50 years of follow-up

BACKGROUND

Pregnancy complications have been recognized as a window to future health. Though cesarean delivery is common, it is unknown whether labor duration and mode of delivery are associated with maternal long-term mortality.

OBJECTIVE

To examine whether labor duration and mode of delivery were associated with all-cause and cause-specific mortality.

STUDY DESIGN

Participants were mothers from the multisite Collaborative Perinatal Project (CPP) cohort (1959-1966; n=43,646, limited to last CPP delivery). We ascertained all-cause and specific causes of death as of 2016 via linkage to the National Death Index and Social Security Death Master File. Hazard ratios (HR) testing mode of delivery and labor duration were estimated using Cox proportional hazards models adjusted for demographic and clinical characteristics. We further stratified analyses by parity.

RESULTS

Among participants with a recorded delivery mode, 5.9% (2486/42,335) had a cesarean delivery. Participants who had a cesarean were older (26.9 vs 24.3 years), with higher body mass index (24.0 vs 22.7 kg/m2), were less likely to be nulliparous (21% vs 30%), and more likely to have a household income of at least $6000 (22% vs 17%), to smoke ≥1 pack/d (18% vs 15%), to have diabetes mellitus (12% vs 1%) and to have a prior medical condition (47% vs 34%), compared to participants with a vaginal delivery. Delivery mode was similar by race/ethnicity, marital status, and education. Median labor duration was 395 minutes among participants who had an intrapartum cesarean delivery and 350 minutes among participants delivered vaginally. By 2016, 52.2% of participants with a cesarean delivery and 38.5% of participants with a vaginal delivery had died. Cesarean vs vaginal delivery was significantly associated with increased risk for all-cause mortality (HR=1.16 (95% confidence interval [CI]: 1.09, 1.23); in nulliparas, HR=1.27 (95% CI: 1.09, 1.47); in multiparas, HR=1.13 (95% CI: 1.06, 1.21) as well as increased risk of death from cardiovascular disease, diabetes, respiratory disease, infection, and kidney disease. Associations with death from cardiovascular disease, infection, and kidney disease were stronger for multiparas than nulliparas, though the association with death from diabetes was stronger among nulliparas. Labor duration was not significantly related to overall mortality.

CONCLUSION

In a historic United States cohort with a low cesarean delivery rate, cesarean delivery was an indicator for subsequent increased mortality risk, particularly related to cardiovascular disease and diabetes. Future studies with long-term follow-up are warranted given the current high prevalence of cesarean delivery.

Survival analysis under imperfect record linkage using historic census data

BACKGROUND

Advancements in linking publicly available census records with vital and administrative records have enabled novel investigations in epidemiology and social history. However, in the absence of unique identifiers, the linkage of the records may be uncertain or only be successful for a subset of the census cohort, resulting in missing data. For survival analysis, differential ascertainment of event times can impact inference on risk associations and median survival.

METHODS

We modify some existing approaches that are commonly used to handle missing survival times to accommodate this imperfect linkage situation including complete case analysis, censoring, weighting, and several multiple imputation methods. We then conduct simulation studies to compare the performance of the proposed approaches in estimating the associations of a risk factor or exposure in terms of hazard ratio (HR) and median survival times in the presence of missing survival times. The effects of different missing data mechanisms and exposure-survival associations on their performance are also explored. The approaches are applied to a historic cohort of residents in Ambler, PA, established using the 1930 US census, from which only 2,440 out of 4,514 individuals (54%) had death records retrievable from publicly available data sources and death certificates. Using this cohort, we examine the effects of occupational and paraoccupational asbestos exposure on survival and disparities in mortality by race and gender.

RESULTS

We show that imputation based on conditional survival results in less bias and greater efficiency relative to a complete case analysis when estimating log-hazard ratios and median survival times. When the approaches are applied to the Ambler cohort, we find a significant association between occupational exposure and mortality, particularly among black individuals and males, but not between paraoccupational exposure and mortality.

DISCUSSION

This investigation illustrates the strengths and weaknesses of different imputation methods for missing survival times due to imperfect linkage of the administrative or registry data. The performance of the methods may depend on the missingness process as well as the parameter being estimated and models of interest, and such factors should be considered when choosing the methods to address the missing event times.

History of multifetal gestation and long-term maternal mortality

BACKGROUND

Multifetal gestation could be associated with higher long-term maternal mortality because it increases the risk of pregnancy complications such as preeclampsia and preterm birth, which are in turn linked to postpartum cardiovascular risk.

OBJECTIVES

We examined whether spontaneously conceived multifetal versus singleton gestation was associated with long-term maternal mortality in a racially diverse U.S.

COHORT

METHODS

We ascertained vital status as of 2016 via linkage to the National Death Index and Social Security Death Master File of 44,174 mothers from the Collaborative Perinatal Project (CPP; 1959-1966). Cox proportional hazards models with maternal age as the time scale assessed associations between history of spontaneous multifetal gestation (in the last CPP observed pregnancy or prior pregnancy) and all-cause and cardiovascular mortality, adjusted for demographics, smoking status, and preexisting medical conditions. We calculated hazard ratios (HR) for all-cause and cause-specific mortality over the study period and until age 50, 60, and 70 years (premature mortality).

RESULTS

Of eligible participants, 1672 (3.8%) had a history of multifetal gestation. Participants with versus without a history of multifetal gestation were older, more likely to have a preexisting condition, and more likely to smoke. By 2016, 51% of participants with and 38% of participants without a history of multifetal gestation had died (unadjusted all-cause HR 1.14, 95% confidence interval [CI] 1.07, 1.23). After adjustment for smoking and preexisting conditions, a history of multifetal gestation was not associated with all-cause (adjusted HR 1.00, 95% CI 0.93, 1.08) or cardiovascular mortality (adjusted HR 0.99, 95% CI 0.87, 1.11) over the study period. However, history of multifetal gestation was associated with an 11% lower risk of premature all-cause mortality (adjusted HR 0.89, 95% CI 0.82, 0.96).

CONCLUSIONS

In a cohort with over 50 years of follow-up, history of multifetal gestation was not associated with all-cause mortality, but may be associated with a lower risk of premature mortality.

"We adjusted for race": now what? A systematic review of utilization and reporting of race in American Journal of Epidemiology and Epidemiology, 2020-2021

Race is a social construct, commonly used in epidemiologic research to adjust for confounding. However, adjustment of race may mask racial disparities, thereby perpetuating structural racism. We conducted a systematic review of articles published in Epidemiology and American Journal of Epidemiology between 2020 and 2021 to (1) understand how race, ethnicity, and similar social constructs were operationalized, used, and reported; and (2) characterize good and poor practices of utilization and reporting of race data on the basis of the extent to which they reveal or mask systemic racism. Original research articles were considered for full review and data extraction if race data were used in the study analysis. We extracted how race was categorized, used-as a descriptor, confounder, or for effect measure modification (EMM)-and reported if the authors discussed racial disparities and systemic bias-related mechanisms responsible for perpetuating the disparities. Of the 561 articles, 299 had race data available and 192 (34.2%) used race data in analyses. Among the 160 US-based studies, 81 different racial categorizations were used. Race was most often used as a confounder (52%), followed by effect measure modifier (33%), and descriptive variable (12%). Fewer than 1 in 4 articles (22.9%) exhibited good practices (EMM along with discussing disparities and mechanisms), 63.5% of the articles exhibited poor practices (confounding only or not discussing mechanisms), and 13.5% were considered neither poor nor good practices. We discuss implications and provide 13 recommendations for operationalization, utilization, and reporting of race in epidemiologic and public health research.

Gestational weight change in a diverse pregnancy cohort and mortality over 50 years: a prospective observational cohort study

BACKGROUND

High weight gain in pregnancy is associated with greater postpartum weight retention, yet long-term implications remain unknown. We aimed to assess whether gestational weight change was associated with mortality more than 50 years later.

METHODS

The Collaborative Perinatal Project (CPP) was a prospective US pregnancy cohort (1959-65). The CPP Mortality Linkage Study linked CPP participants to the National Death Index and Social Security Death Master File for vital status to 2016. Adjusted hazard ratios (HRs) with 95% CIs estimated associations between gestational weight gain and loss according to the 2009 National Academy of Medicine recommendations and mortality by pre-pregnancy BMI. The primary endpoint was all-cause mortality. Secondary endpoints included cardiovascular and diabetes underlying causes of mortality.

FINDINGS

Among 46 042 participants, 20 839 (45·3%) self-identified as Black and 21 287 (46·2%) as White. Median follow-up time was 52 years (IQR 45-54) and 17 901 (38·9%) participants died. For those who were underweight before pregnancy (BMI <18·5 kg/m2; 3809 [9·4%] of 40 689 before imputation for missing data]), weight change above recommendations was associated with increased cardiovascular mortality (HR 1·84 [95% CI 1·08-3·12]) but not all-cause mortality (1·14 [0·86-1·51]) or diabetes-related mortality (0·90 [0·13-6·35]). For those with a normal pre-pregnancy weight (BMI 18·5-24·9 kg/m2; 27 921 [68·6%]), weight change above recommendations was associated with increased all-cause (HR 1·09 [1·01-1·18]) and cardiovascular (1·20 [1·04-1·37]) mortality, but not diabetes-related mortality (0·95 [0·61-1·47]). For those who were overweight pre-pregnancy (BMI 25·0-29·9 kg/m2; 6251 [15·4%]), weight change above recommendations was associated with elevated all-cause (1·12 [1·01-1·24]) and diabetes-related (1·77 [1·23-2·54]) mortality, but not cardiovascular (1·12 [0·94-1·33]) mortality. For those with pre-pregnancy obesity (≥30·0 kg/m2; 2708 [6·7%]), all associations between gestational weight change and mortality had wide CIs and no meaningful relationships could be drawn. Weight change below recommended levels was associated only with a reduced diabetes-related mortality (0·62 [0·48-0·79]) in people with normal pre-pregnancy weight.

INTERPRETATION

This study's novel findings support the importance of achieving healthy gestational weight gain within recommendations, adding that the implications might extend beyond the pregnancy window to long-term health, including cardiovascular and diabetes-related mortality.

FUNDING

National Institutes of Health.

Pregnancy Complications and Long-Term Mortality in a Diverse Cohort

BACKGROUND

Pregnancy complications are associated with increased risk of development of cardiometabolic diseases and earlier mortality. However, much of the previous research has been limited to White pregnant participants. We aimed to investigate pregnancy complications in association with total and cause-specific mortality in a racially diverse cohort and evaluate whether associations differ between Black and White pregnant participants.

METHODS

The Collaborative Perinatal Project was a prospective cohort study of 48 197 pregnant participants at 12 US clinical centers (1959-1966). The Collaborative Perinatal Project Mortality Linkage Study ascertained participants' vital status through 2016 with linkage to the National Death Index and Social Security Death Master File. Adjusted hazard ratios (aHRs) for underlying all-cause and cause-specific mortality were estimated for preterm delivery (PTD), hypertensive disorders of pregnancy, and gestational diabetes/impaired glucose tolerance (GDM/IGT) using Cox models adjusted for age, prepregnancy body mass index, smoking, race and ethnicity, previous pregnancies, marital status, income, education, previous medical conditions, site, and year.

RESULTS

Among 46 551 participants, 45% (21 107 of 46 551) were Black, and 46% (21 502 of 46 551) were White. The median time between the index pregnancy and death/censoring was 52 years (interquartile range, 45-54). Mortality was higher among Black (8714 of 21 107 [41%]) compared with White (8019 of 21 502 [37%]) participants. Overall, 15% (6753 of 43 969) of participants had PTD, 5% (2155 of 45 897) had hypertensive disorders of pregnancy, and 1% (540 of 45 890) had GDM/IGT. PTD incidence was higher in Black (4145 of 20 288 [20%]) compared with White (1941 of 19 963 [10%]) participants. The following were associated with all-cause mortality: preterm spontaneous labor (aHR, 1.07 [95% CI, 1.03-1.1]); preterm premature rupture of membranes (aHR, 1.23 [1.05-1.44]); preterm induced labor (aHR, 1.31 [1.03-1.66]); preterm prelabor cesarean delivery (aHR, 2.09 [1.75-2.48]) compared with full-term delivery; gestational hypertension (aHR, 1.09 [0.97-1.22]); preeclampsia or eclampsia (aHR, 1.14 [0.99-1.32]) and superimposed preeclampsia or eclampsia (aHR, 1.32 [1.20-1.46]) compared with normotensive; and GDM/IGT (aHR, 1.14 [1.00-1.30]) compared with normoglycemic. P values for effect modification between Black and White participants for PTD, hypertensive disorders of pregnancy, and GDM/IGT were 0.009, 0.05, and 0.92, respectively. Preterm induced labor was associated with greater mortality risk among Black (aHR, 1.64 [1.10-2.46]) compared with White (aHR, 1.29 [0.97-1.73]) participants, while preterm prelabor cesarean delivery was higher in White (aHR, 2.34 [1.90-2.90]) compared with Black (aHR, 1.40 [1.00-1.96]) participants.

CONCLUSIONS

In this large, diverse US cohort, pregnancy complications were associated with higher mortality nearly 50 years later. Higher incidence of some complications in Black individuals and differential associations with mortality risk suggest that disparities in pregnancy health may have life-long implications for earlier mortality.

Infant sex at birth and long-term maternal mortality

BACKGROUND

Maternal adaptations may vary by foetal sex. Whether male infants influence long-term mortality in mothers remains uncertain.

OBJECTIVE

The objective of the study was to examine whether male infants increase the risk of maternal mortality.

METHODS

This study included pregnant women enrolled at 12 US sites from 1959 to 1966 in the Collaborative Perinatal Project (CPP). Collaborative Perinatal Project records were linked to the National Death Index and the Social Security Master Death File to ascertain deaths until 2016. Foetal sex was determined by infant sex at birth, defined as the total number of male or female infants in pregnancies prior to or during enrolment in the CPP. In secondary analyses, exposure was defined as infant sex at the last CPP delivery. Outcomes included all-cause and underlying causes of mortality. We used Cox proportional hazards models weighted by the number of prior live births and stratified our models by parity and race/ethnicity.

RESULTS

Among 48,188 women, 50.8% had a male infant at their last registered CPP pregnancy and 39.0% had a recorded death after a mean follow-up of 47.8 years (SD 10.5 years). No linear association was found between the number of liveborn males and all-cause mortality (primipara women: HR 1.02, 95% CI 0.95, 1.09, multipara women, 1 prior live birth: HR 0.96, 95% CI 0.89, 1.03, multipara women, ≥2 prior live births: HR 0.97, 95% CI 0.85, 1.11). A similar trend was noted for cardiovascular- and cancer-related mortality. At the last delivery, women with a male infant did not have an increased risk of all-cause or cause-specific mortality compared to women with a female infant. These findings were consistent across racial/ethnic groups.

CONCLUSIONS

Women who give birth to male infants, regardless of number, are not at increased risk of all-cause and cause-specific mortality. These findings suggest that giving birth to male infants may not independently influence the long-term health of women.

Long-Term Mortality in Women With Pregnancy Loss and Modification by Race/Ethnicity

Pregnancy loss is a common reproductive complication, but its association with long-term mortality and whether this varies by maternal race/ethnicity is not well understood. Data from a racially diverse cohort of pregnant women enrolled in the Collaborative Perinatal Project (CPP) from 1959 to 1966 were used for this study. CPP records were linked to the National Death Index and the Social Security Death Master File to identify deaths and underlying cause (until 2016). Pregnancy loss comprised self-reported losses, including abortions, stillbirths, and ectopic pregnancies. Among 48,188 women (46.0% White, 45.8% Black, 8.2% other race/ethnicity), 25.6% reported at least 1 pregnancy loss and 39% died. Pregnancy loss was associated with a higher absolute risk of all-cause mortality (risk difference, 4.0 per 100 women, 95% confidence interval: 1.4, 6.5) and cardiovascular mortality (risk difference, 2.2 per 100 women, 95% confidence interval: 0.8, 3.5). Stratified by race/ethnicity, a higher risk of mortality persisted in White, but not Black, women. Women with recurrent losses are at increased risk of death, both overall and across all race/ethnicity groups. Pregnancy loss is associated with death; however, it does not confer an excess risk above the observed baseline risk in Black women. These findings support the need to assess reproductive history as part of routine screening in women.

Placental characteristics and risks of maternal mortality 50 years after delivery

INTRODUCTION

Adverse pregnancy outcomes such as preterm delivery and preeclampsia are associated with a higher maternal risk for subsequent cardiovascular disease (CVD) and all-cause mortality. While such pregnancy conditions are related to abnormal placentation, little research has investigated whether pathologic placental measures could serve as a risk factor for future CVD mortality in mothers.

METHODS

Longitudinal study of 33,336 women from the Collaborative Perinatal Project (CPP; 1959-1966) linked to mortality information through December 2016. Pathologists took extensive morphological and histopathological measures. Apart from assessing associations with morphological features, we derived an overall composite score and specific inflammation-related, hemorrhage-related, and hypoxia-related pathologic placenta index scores. Cox regression estimated hazard ratios (HR) and 95% confidence intervals (CI) for mortality adjusting for covariates.

RESULTS

Thirty-nine percent of women died with mean (standard deviation, SD) time to death of 39 (12) years. Mean (SD) placental weight and birthweight were 436 g (98) and 3156 g (566), respectively. Placenta-to-birthweight ratio was associated with all-cause mortality (adjusted HR 1.03: 1.01, 1.05 per SD in ratio). In cause-specific analyses, it was significantly associated with respiratory (HR 1.06), dementia (HR: 1.10) and liver (HR 1.04) related deaths. CVD, cancer, diabetes and kidney related deaths also tended to increase, whereas infection related deaths did not (HR 0.94; 0.83, 1.06). Placental measures of thickness, diameters, and histopathological measures grouped by inflammatory, hemorrhagic, or hypoxic etiology were not associated with mortality.

DISCUSSION

Placental weight in relation to birthweight was associated with long-term maternal mortality but other histopathologic or morphologic features were not.