Stillbirth in Canada: anachronistic definition and registration processes impede public health surveillance and clinical care

Effect of the COVID-19 Pandemic on Stillbirths in Canada and the United States

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.

The impact of isolated obesity compared with obesity and other risk factors on risk of stillbirth: a retrospective cohort study

BACKGROUND

Maternal obesity is associated with stillbirth, but uncertainty persists around the effects of higher obesity classes. We sought to compare the risk of stillbirth associated with maternal obesity alone versus maternal obesity and additional or undiagnosed factors contributing to high-risk pregnancy.

METHODS

We conducted a retrospective cohort study using the Better Outcomes Registry and Network (BORN) for singleton hospital births in Ontario between 2012 and 2018. We used multivariable Cox proportional hazard regression and logistic regression to evaluate the relationship between prepregnancy maternal body mass index (BMI) class and stillbirth (reference was normal BMI). We treated maternal characteristics and obstetrical complications as independent covariates. We performed mediator analyses to measure the direct and indirect effects of BMI on stillbirth through major common-pathway complications. We used fully adjusted and partially adjusted models, representing the impact of maternal obesity alone and maternal obesity with other risk factors on stillbirth, respectively.

RESULTS

We analyzed data on 681 178 births between 2012 and 2018, of which 1956 were stillbirths. Class I obesity was associated with an increased incidence of stillbirth (adjusted hazard ratio [HR] 1.55, 95% confidence interval [CI] 1.35-1.78). This association was stronger for class III obesity (adjusted HR 1.80, 95% CI 1.44-2.24), and strongest for class II obesity (adjusted HR 2.17, 95% CI 1.83-2.57). Plotting point estimates for odds ratios, stratified by gestational age, showed a marked increase in the relative odds for stillbirth beyond 37 weeks' gestation for those with obesity with and without other risk factors, compared with those with normal BMI. The impact of potential mediators was minimal.

INTERPRETATION

Maternal obesity alone and obesity with other risk factors are associated with an increased risk of stillbirth. This risk increases with gestational age, especially at term.

Miscarriage after SARS-CoV-2 vaccination: A population-based cohort study

OBJECTIVE

To evaluate the risk of miscarriage following SARS-CoV-2 vaccination, while accounting for the competing risk of induced abortion.

DESIGN

Population-based cohort study.

SETTING

Ontario, Canada.

PARTICIPANTS

Women aged 15-50 years with a confirmed pregnancy at ≤19 completed weeks' gestation.

METHODS

Exposure to first SARS-CoV-2 vaccination, handled in a time-varying manner, was defined as (i) unvaccinated, (ii) remotely vaccinated >28 days before the estimated conception date or (iii) recently vaccinated ≤28 days before conception and up to 120 days after conception.

MAIN OUTCOME MEASURES

The outcome was miscarriage, occurring between the estimated date of conception and up to 19 completed weeks of pregnancy. Fine-Grey hazard models, accounting for the competing risk of induced abortion, generated hazard ratios (aHR), adjusted for socio-demographic factors, comorbidities, and biweekly periods.

RESULTS

Included were 246 259 pregnant women, of whom 34% received a first SARS-CoV-2 vaccination. Miscarriage occurred at a rate of 3.6 per 10 000 person-days among remotely vaccinated women and 3.2 per 10 000 person-days among those recently vaccinated, in contrast to a rate of 1.9 per 10 000 person-days among unvaccinated women, with corresponding aHR of 0.98 (95% confidence interval [CI] 0.91-1.07) and 1.00 (95% CI 0.93-1.08).

CONCLUSIONS

SARS-CoV-2 vaccination was not associated with miscarriage while accounting for the competing risk of induced abortion. This study reiterates the importance of including pregnant women in new vaccine clinical trials and registries, and the rapid dissemination of vaccine safety data.

Etiology of stillbirth in a tertiary care center: a retrospective cohort study assessing ultrasound, laboratory, and pathology investigations

BACKGROUND

Canadian stillbirth data are limited, and a significant proportion of pregnancies resulting in stillbirth have no attributable cause. The objective of this study was to characterize stillbirth case investigations and management at a tertiary care hospital in Ontario, Canada.

METHODS

This was a retrospective chart review study of all cases of singleton stillbirth at The Ottawa Hospital between 1 January 2012 and 31 December 2017. Terminations and multiples stillbirths were excluded. Chart reviews were conducted to extract maternal sociodemographic, obstetrical, and fetal characteristics, including results from antenatal ultrasounds, autopsy, placenta pathology, and laboratory investigations.

RESULTS

A total of 155 eligible cases of stillbirth were identified, resulting in a 6-year stillbirth rate of 4.2 per 1000 total births. The median maternal age was 31.0 years (IQR: 29.0, 35.0) and the median gestational age at delivery was 28 weeks (IQR: 24, 35). A total of 9 (5.8%) pregnant individuals had a history of previous stillbirth. Of the 155 stillbirths, 35% underwent the full suite of post-loss laboratory, placental, and fetal autopsy investigations. 63.2% of cases had post-loss laboratory investigations completed. 76% and 71% of cases had fetal autopsy and placenta pathology evaluations completed, respectively. Antenatal characteristics associated with stillbirth included fetal anomalies/genetic markers (27.1%), umbilical cord and placental anomalies (24.5%), fetal growth abnormalities (27.7%), cervical/uterine abnormalities (11.6%), and amniotic fluid abnormalities (25.1%). The most common autopsy findings included evidence of infection (22.7%), fetal anomalies (12.6%), and fetal hypoxia (10%). The most common placental pathology findings included features of placental insufficiency (21.8%), retroplacental abnormalities (16.3%), and umbilical cord accident/infarct (15.4%).

CONCLUSIONS

Our findings demonstrate that as many as two-thirds of singleton stillbirth cases at our center did not receive the post-perinatal loss investigations recommended by clinical practice guidelines. More thorough collection of post-stillbirth data at all levels (institutional, provincial, national) is warranted to improve our understanding of stillbirth epidemiology, etiology, and management in Canada.

Pregnancy outcomes during the COVID-19 pandemic in Canada, March to August 2020

OBJECTIVE

Several studies have documented changes in the rates preterm birth and stillbirth during the COVID-19 pandemic. We carried out a study to examine obstetric intervention, preterm birth, and stillbirth rates in Canada from March to August 2020.

METHODS

The study included all singleton hospital deliveries in Canada (excluding Québec) from March to August 2020 (and March to August for the years 2015-2019) with information obtained from the Canadian Institute for Health Information. Data for Ontario were examined separately because this province had the highest rates of COVID-19 in the study population. Rates and odds ratios with 95% confidence intervals (CIs) were used to quantify pregnancy-related outcomes.

RESULTS

There were 136,445 and 717,905 singleton hospital deliveries in Canada (excluding Quebéc) in from March to August 2020 and between March and August 2015-2019, respectively. Rates of obstetric intervention declined in early gestation in 2020. Odds ratios for labour induction and cesarean delivery at <32 weeks gestation for March-August 2020 versus March-August in 2015 to 2019 were 0.84 (95% CI 0.74-0.95) and 0.92 (95% CI 0.85-1.00), respectively. Preterm birth rates increased in Canada (excluding Québec) from 6.42% in March-August 2015 to 6.74% in March-August 2019 but were unchanged in March-August 2020 (6.74%). Stillbirth rates were stable between March-August 2015 and March-August 2020. However, stillbirth rates peaked in Ontario in April 2020 due to higher rates of stillbirths at 20-27 and 37-41 weeks gestation.

CONCLUSION

Changes in labour induction and cesarean delivery at early gestation and other perinatal outcomes during the period of March to August 2020 highlight the need to reconsider the use and impact of obstetric services in pandemics as well as the need for timely perinatal surveillance.