Hypertensive Disorders in Pregnancy and Mortality at Delivery Hospitalization — United States, 2017–2019

Nicole D. Ford, PhD; Shanna Cox, MSPH; Jean Y. Ko, PhD; Lijing Ouyang, PhD; Lisa Romero, DrPh; Tiffany Colarusso, MD; Cynthia D. Ferre, MA; Charlan D. Kroelinger, PhD; Donald K. Hayes, MD; Wanda D. Barfield, MD

Disclosures

Morbidity and Mortality Weekly Report. 2022;71(17):585-591. 

Abstract and Introduction

Introduction

Hypertensive disorders in pregnancy (HDPs), defined as prepregnancy (chronic) or pregnancy-associated hypertension, are common pregnancy complications in the United States.* HDPs are strongly associated with severe maternal complications, such as heart attack and stroke,[1] and are a leading cause of pregnancy-related death in the United States. CDC analyzed nationally representative data from the National Inpatient Sample to calculate the annual prevalence of HDP among delivery hospitalizations and by maternal characteristics, and the percentage of in-hospital deaths with an HDP diagnosis code documented. During 2017–2019, the prevalence of HDP among delivery hospitalizations increased from 13.3% to 15.9%. The prevalence of pregnancy-associated hypertension increased from 10.8% in 2017 to 13.0% in 2019, while the prevalence of chronic hypertension increased from 2.0% to 2.3%. Prevalence of HDP was highest among delivery hospitalizations of non-Hispanic Black or African American (Black) women, non-Hispanic American Indian and Alaska Native (AI/AN) women, and women aged ≥35 years, residing in zip codes in the lowest median household income quartile, or delivering in hospitals in the South or the Midwest Census regions. Among deaths that occurred during delivery hospitalization, 31.6% had any HDP documented. Clinical guidance for reducing complications from HDP focuses on prompt identification and preventing progression to severe maternal complications through timely treatment.[1] Recommendations for identifying and monitoring pregnant persons with hypertension include measuring blood pressure throughout pregnancy,§ including self-monitoring. Severe complications and mortality from HDP are preventable with equitable implementation of strategies to identify and monitor persons with HDP[1] and quality improvement initiatives to improve prompt treatment and increase awareness of urgent maternal warning signs.[2]

Delivery hospitalization data for 2017–2019 were analyzed from the National Inpatient Sample, a nationally representative sample of all U.S. hospital discharges. CDC identified delivery hospitalizations among females aged 12–55 years using International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) diagnosis and procedure codes pertaining to delivery and diagnosis-related group delivery codes.** HDPs were categorized using ICD-10-CM diagnosis codes†† for chronic hypertension,§§ pregnancy-associated hypertension,¶¶ and unspecified maternal hypertension. Deaths were identified based on patient hospital discharge disposition.

Weighted annual prevalence (percentage) and 95% CI for HDP overall and by each type were calculated. Change in annual prevalence of HDP overall and by type was assessed using a linear trend test. Pooling data from this period, CDC calculated the weighted prevalence and 95% CIs for HDP by selected maternal characteristics (i.e., age group, race and ethnicity, and primary payer at delivery hospitalization) and characteristics of the community in which they lived (i.e., county-level rural-urban classification, zip code–level median household income, and hospital region).*** Rao-Scott chi-square tests of independence were used to assess whether HDP prevalence differed by characteristics. Percentage of deaths during delivery hospitalization with a documented HDP diagnosis code were calculated. All analyses were conducted using SAS software (version 9.4; SAS Institute); SAS survey procedures and weighting were used to account for complex sampling in the National Inpatient Sample. This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy.†††

During 2017–2019, the prevalence of HDP among delivery hospitalizations increased from 13.3% to 15.9% (Figure 1), an increase of approximately 1 percentage point annually. Linear trend tests suggested that change in annual prevalence of HDP overall, pregnancy-associated hypertension, and chronic hypertension increased during 2017–2019, while prevalence of unspecified maternal hypertension remained stable. The prevalence of pregnancy-associated hypertension increased from 10.8% to 13.0% and that of chronic hypertension increased from 2.0% to 2.3%.

Figure 1.

Prevalence of hypertensive disorders in pregnancy* among delivery hospitalizations, by year — National Inpatient Sample, United States, 2017–2019
Abbreviations: HDP = hypertensive disorder in pregnancy; HTN = hypertension; PAH = pregnancy-associated hypertension.
*HDPs are defined as chronic hypertension, pregnancy-associated hypertension (i.e., gestational hypertension, preeclampsia, eclampsia, and chronic hypertension with superimposed preeclampsia), and unspecified maternal hypertension.

During 2017–2019 combined, prevalence of HDP overall was 14.6%. Prevalence varied overall and by HDP type for all maternal characteristics evaluated in the study (Table). Prevalence of any HDP was higher among delivery hospitalizations to women aged 35–44 (18.0%) and 45–55 years (31.0%) than to younger women, to Black (20.9%) and AI/AN (16.4%) women than to women of other racial and ethnic groups, to those residing in rural counties (15.5%) and in zip codes in the lowest median household-level income quartile (16.4%) than those residing in metropolitan or micropolitan counties or in zip codes in higher household-level income quartiles, or delivering in hospitals in the South (15.9%) or Midwest (15.0%) U.S. Census regions than in other Census regions. These differences in HDP prevalence were similar across HDP types.

Among maternal deaths that occurred during delivery hospitalization, 31.6% had any HDP documented and 24.3% had pregnancy-associated hypertension documented. Chronic or unspecified maternal hypertension was documented in 7.4% of deaths §§§ (Figure 2).

Figure 2.

Proportion of deaths* occurring during delivery hospitalization with a documented diagnosis code of a hypertensive disorder in pregnancy— National Inpatient Sample, United States, 2017–2019
Abbreviation: HDP = hypertensive disorder in pregnancy.
*This study did not assign cause of death but instead examined the proportion of in-hospital deaths with an HDP diagnosis code documented among delivery hospitalizations.
HDPs are defined as chronic hypertension, pregnancy-associated hypertension (i.e., gestational hypertension, preeclampsia, eclampsia, and chronic hypertension with superimposed preeclampsia), and unspecified maternal hypertension. Proportions for chronic and unspecified maternal hypertension are combined to conform to the Agency for Healthcare Research and Quality's data use agreement, which prohibits reporting estimates based on fewer than 11 unweighted observations.

*https://www.cdc.gov/reproductivehealth/maternalinfanthealth/pregnancy-complications-data.htm
https://www.cdc.gov/reproductivehealth/maternal-mortality/pregnancy-mortality-surveillance-system.htm?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Freproductivehealth%2Fmaternalinfanthealth%2Fpregnancy-mortality-surveillance-system.htm#causes
§The U.S. Preventive Services Task Force recommends screening for preeclampsia in pregnant women with blood pressure measurements throughout pregnancy. https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/preeclampsia-screening
https://www.hcup-us.ahrq.gov/db/nation/nis/nisdbdocumentation.jsp
**Delivery hospitalizations were identified using ICD-10-CM diagnosis codes (Z370, Z371, Z372, Z373, Z374, Z3750, Z3751, Z3752, Z3753, Z3754, Z3759, Z3760, Z3761, Z3762, Z3763, Z3764, Z3769, Z377, Z379, O7582, O80, and O82), procedure codes (10D00Z0, 10D00Z1, 10D00Z2, 10D07Z3, 10D07Z4, 10D07Z5, 10D07Z6, 10D07Z7, 10D07Z8, and 10E0XZZ) and diagnosis-related group codes (765, 766, 767, 768, 774, and 775 through September 2018 and 768, 783, 784, 785, 786, 787, 788, 796, 797, 798, 805, 806, and 807 beginning in October 2018). Ectopic and molar pregnancies and pregnancies with abortive outcomes were excluded. CDC excluded an additional 382 delivery hospitalizations that were missing discharge disposition of the patient.
††Hypertensive disorders in pregnancy were identified using ICD-10-CM diagnosis codes for chronic hypertension (O100, O101, O102, O103, O109, O104, I10, I11, I12, I13, and I15), pregnancy-associated hypertension (chronic hypertension with superimposed preeclampsia [O11], preeclampsia [O14], eclampsia [O15], gestational hypertension [O13]), and unspecified maternal hypertension (O16).
§§Chronic hypertension is defined as hypertension diagnosed or present before pregnancy or before 20 weeks of gestation. https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2019/01/chronic-hypertension-in-pregnancy
¶¶Pregnancy-associated hypertension includes gestational hypertension, preeclampsia, eclampsia, and chronic hypertension with superimposed preeclampsia. Gestational hypertension is defined as hypertension occurring after 20 weeks of gestation in persons with previously normal blood pressure. Preeclampsia is defined as gestational hypertension with new-onset proteinuria. In the absence of proteinuria, preeclampsia might be diagnosed in cases of gestational hypertension with new onset thrombocytopenia, renal insufficiency, impaired liver function, pulmonary edema, visual symptoms, or headache unresponsive to medication and not accounted for by alternative diagnoses. Eclampsia is defined as new-onset tonic-clonic, focal, or multifocal seizures in the absence of other causative conditions. Chronic hypertension with superimposed preeclampsia is defined as preeclampsia in women with a history of hypertension before pregnancy or before 20 weeks of gestation. https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2020/06/gestational-hypertension-and-preeclampsia
***Patient age in years at hospital admission was calculated from the patient birth date and admission date. The Healthcare Cost and Utilization Project (HCUP) classifies race and ethnicity based on separate race and ethnicity data elements. In HCUP's combined race and ethnicity data element, ethnicity takes precedence over race (i.e., patients with Hispanic ethnicity are classified as Hispanic, and non-Hispanic patients are classified according to their reported race). The HCUP race and ethnicity category Native American is expressed as American Indian and Alaska Native in this report. Payer indicates the expected primary payer and was categorized as private, public (Medicare or Medicaid), or other (self-pay, no charge, or other). Rurality is based on the urban-rural classification of the patient's county, according to the CDC National Center for Health Statistics urban-rural classification for health care research. Rurality was categorized as metropolitan, micropolitan, and rural (nonmetropolitan and nonmicropolitan). HCUP obtains hospital Census region, as defined by the U.S. Census Bureau, from the American Hospital Association's Annual Survey of Hospitals.
†††45 C.F.R. part 46.102(l)(2), 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect. 552a; 44 U.S.C. Sect. 3501 et seq.
§§§Proportions for chronic and unspecified maternal hypertension are combined to conform to the Agency for Healthcare Research and Quality's Data Use Agreement which prohibits reporting estimates based on fewer than 11 unweighted observations.

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