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Am J Perinatol 2023; 40(05): 467-474
DOI: 10.1055/a-1925-1532
SMFM Fellowship Series Article

Prospective Observational Study of N-terminal Pro–Brain Natriuretic Peptide Levels in Obese and Nonobese Women during Pregnancy

Anna E. Denoble    *
1   Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Duke University Health System, Durham, North Carolina
,
Julia M. Moyett
2   Duke University School of Medicine, Duke University, Durham, North Carolina
,
Sarah A. Goldstein
3   Division of Cardiology, Department of Medicine, Duke University Health System, Durham, North Carolina
,
Cary C. Ward
3   Division of Cardiology, Department of Medicine, Duke University Health System, Durham, North Carolina
,
Tracy Truong
4   Department of Biostatistics and Bioinformatics, Duke University Health System, Durham, North Carolina
,
Alaattin Erkanli
4   Department of Biostatistics and Bioinformatics, Duke University Health System, Durham, North Carolina
,
Andra H. James
1   Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Duke University Health System, Durham, North Carolina
,
Chad A. Grotegut
5   Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Wake Forest Baptist Health System, Winston-Salem, North Carolina
› Author Affiliations
Funding This study was generously supported by funding from the Duke Department of Obstetrics and Gynecology Hammond Research Fund. The Duke BERD Methods Core's support of this project was made possible in part by CTSA grant (UL1TR002553) from the National Center for Advancing Translational Sciences (NCATS) of the National Institutes of Health (NIH), and the NIH Roadmap for Medical Research. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of NCATS or NIH.
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Abstract

Objective N-terminal pro–brain natriuretic peptide (NT-proBNP), a marker of ventricular dysfunction, varies by body mass index (BMI) outside of pregnancy. This study aimed to determine whether obesity affects NT-proBNP levels in pregnancy.

Study Design This was a prospective observational study of healthy pregnant people in the third trimester (3TM) and postpartum (PP). Patients were excluded if they had significant medical comorbidities or if their fetuses had anomalies, growth restriction or aneuploidy. NT-proBNP was measured at 28 weeks (3TM), predelivery (PD), 1 to 2 days PP (immediate postpartum [IPP]), and 4 to 6 weeks PP (delayed postpartum [DPP]). LogNT-proBNP levels were analyzed using linear mixed effects models, including BMI < or ≥30, time, and time-by-BMI interactions.

Results Fifty-five people (28 [51%] with BMI ≥ 30 and 27 [49%] with BMI < 30) were enrolled. A greater proportion of obese than nonobese subjects developed hypertensive disorders of pregnancy (50 vs. 15%, p = 0.010) and obese patients had higher systolic blood pressures at all time points (p < 0.05). NT-proBNP levels (median [interquartile range] in pg/mL) were 18 (6–28) versus 26 (17–48) at 3TM, 16 (3–38) versus 43 (21–60) at PD, 58 (20–102) versus 63 (38–155) at IPP, and 33 (27–56) versus 23 (8–42) at DPP for obese compared with nonobese patients. In linear mixed effects models, logNT-proBNP was lower in obese patients at 3TM (β = −0.89 [95% confidence interval, CI: −1.51, −0.26]) and PD (β = −1.05 [95% CI: −1.72, −0.38]). The logNT-proBNP trends over time differed by BMI category, with higher values in obese patients at both PP time points compared with the 3TM (IPP β = 1.24 [95% CI: 0.75, 1.73]; DPP β = 1.08 [95% CI: 0.52, 1.63]), but only IPP for nonobese patients (β = 0.87 [95% CI: 0.36, 1.38]).

Conclusion Obese patients had lower NT-proBNP levels than nonobese patients during pregnancy but not PP. The prolonged PP elevation in NT-proBNP in obese patients suggests that their PP cardiac recovery may be more prolonged.

Key Points

  • NT-proBNP levels are lower in obese than nonobese patients during pregnancy.

  • Levels remain elevated in obese, but not nonobese, patients up to 4 to 6 weeks' postpartum.

  • A lower threshold for concern regarding NT-proBNP levels may be needed in obese pregnant people.

Keywords

pregnancy - N-terminal pro–brain natriuretic peptide - brain natriuretic peptide - heart failure - obesity - peripartum cardiomyopathy

Conference Presentation

This manuscript was presented in poster format at the Society for Maternal-Fetal Medicine's 41st Annual Pregnancy Meeting (virtual), which was held on January 25–30, 2021.


Clinical Trial Registration

The study is registered with Clinical Trials.gov (https://clinicaltrials.gov/ct2/show/NCT04049136).


* Present address: Section of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, CT.




Publication History

Received: 12 January 2022

Accepted: 11 August 2022

Accepted Manuscript online:
16 August 2022

Article published online:
30 December 2022

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