Aspirin Use for Preeclampsia Prevention Among Women With Prepregnancy Diabetes, Obesity, and Hypertension

In large cohort studies, preeclampsia has been found to affect 7.3% of pregnant women with and 2.7% of those without clinical risk factors.¹ The US Preventive Services Task Force (USPSTF) recommended in 2014 (and reiterated in 2021) that low-dose (81 mg) aspirin be started after 12 weeks’ gestation in all women at high risk for preeclampsia as well as in women with combinations of moderate-level risk factors (B recommendation).^2,3 Although there are a number of risk factors for preeclampsia,¹ prepregnancy diabetes and chronic hypertension are common factors that are ranked by the USPSTF as high level and tend to cluster in women with obesity.^1,4

Obesity is rated as a moderate-level risk factor,² yet it is associated with a high population attributable fraction of 18% for preeclampsia.¹ Single-center survey data from 2012-2015 suggest that only 7.6% of eligible women are prescribed aspirin⁵ despite it conferring a relative risk reduction of 10%-50% against preeeclampsia.^1,2 The current study estimated aspirin use for preeclampsia prevention in pregnant women with prepregnancy diabetes, obesity, chronic hypertension, and combinations of these factors in 2018-2020.

This population-based study was completed in Ontario, Canada’s largest and most ethnically diverse province with a universal health care system. Included were all women with a hospital livebirth or stillbirth at 23 weeks’ gestation or greater from April 1, 2018, through December 31, 2020.

Data were obtained from the Better Outcomes Registry and Network (BORN) Ontario, a provincially mandated birth registry. All hospitalized birth data are collected by health care professionals and hospital staff from charts, clinical forms, and patient interviews and then entered into the BORN information system, which contains demographics, clinical details, and a specific yes or no field for response to the following comment: “ASA [aspirin] taken daily for preeclampsia prevention, any time after 12 weeks’ gestation.” The variable has not been validated against chart abstraction, although other BORN variables have been validated.

Maternal and newborn characteristics are presented for women with diabetes, obesity, or chronic hypertension. Rates of aspirin use overall and among those with diabetes, obesity, or hypertension were calculated with 95% CIs using SAS version 9.4 software (SAS Institute Inc).

This study was approved by the research ethics board at Unity Health. Under the Personal Health Information Protection Act of 2004, BORN can collect and use personal health information without consent.

During the study period, 371 237 births were included (Table 1). In contrast to those without the condition, pregnant women with diabetes, obesity, or hypertension tended to be older, have a higher body mass index, more preterm birth, and a longer hospital length of stay.

Women with diabetes, obesity, or hypertension (77 582) comprised 20.9% of the sample. Aspirin was used by 3.2% (95% CI, 3.2%-3.3%) of women without any of the 3 risk factors. The rate of aspirin use was 17.2% (95% CI, 16.2%-18.2%) in women with diabetes, 6.9% (95% CI, 6.7%-7.1%) in women with obesity, and 27.6% (95% CI, 26.2%-29.0%) in women with hypertension.

The rate of aspirin use was 22.2% (95% CI, 20.5%-24.0%) in women with diabetes and obesity, 36.6% (95% CI, 31.9%-41.6%) in women with diabetes and hypertension, 32.3% (95% CI, 30.2%-34.5%) in women with obesity and hypertension, and 38.8% (32.9%-44.9%) in women with all 3 factors (Table 2).

In this contemporary population-based study, aspirin was used for preeclampsia prophylaxis in a minority of women with prepregnancy diabetes, obesity, or chronic hypertension, or a combination of these factors, in whom it is recommended.

Limitations include the inability to capture the timing, dose, or duration of aspirin use and the possibility that aspirin consumption was underreported. Only 3 of multiple risk factors for preeclampsia were examined,¹ and direct measures of glycemic or blood pressure control were lacking. Rare contraindications to aspirin, such as aspirin allergy or thrombocytopenia, were not recorded. The findings may not be generalizable to other jurisdictions, although the cohort was multiracial and low rates of aspirin use have been observed in other countries,⁵ including in the US.⁶

For the 2021 USPSTF recommendations to be more influential,³ more data are needed to characterize barriers for aspirin adoption among suitable women at the patient and practitioner level, and additional knowledge translation initiatives developed.

Accepted for Publication: December 2, 2021.

Corresponding Author: Joel G. Ray, MD, MSc, Department of Medicine, St Michael’s Hospital, 30 Bond St, Toronto, ON M5B 1W8, Canada (rayj@smh.ca).

Author Contributions: Mr Abdulaziz had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Ray, Berger.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Ray.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Ray, Abdulaziz.

Obtained funding: Ray.

Conflict of Interest Disclosures: None reported.

Funding/Support: This work was supported by grant 146442 from the Canadian Institutes for Health Research.

Role of the Funder/Sponsor: The Canadian Institutes for Health Research had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Group Information: A complete list of the members of the DOH-NET (Diabetes, Obesity, and Hypertension in Pregnancy Research Network) appears in reference 1.