USA: A recent study published in JACC: Advances has shown significantly higher NT-proBNP (N-terminal pro-B-type natriuretic peptide) in women in their pregnancy's first trimester compared to similarly aged nonpregnant women.
The researchers suggest "the dynamic nature of NT-proBNP should be considered when ordering NT-proBNP lab tests in pregnant women."
The pro-B-type natriuretic peptide is a prohormone cleaved into biologically active BNP and NT-proBNP. NT-proBNP is often used as an adjunct clinical measure for heart failure evaluation. Not much is known about expected physiologic NT-proBNP levels in pregnancy. Currently, there are no recognized reference values for NT-proBNP in pregnant women, making it challenging to interpret NT-proBNP in this setting. There have been no studies of NT-proBNP in a general population of pregnant women in the US. As NT-proBNP is often used for its negative predictive value, it is crucial to understand its distribution in the general population.

To fill this knowledge gap, Anum S. Minhas, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA, and colleagues aimed to measure NT-proBNP in adult women, by trimester and pregnancy status, in a nationally representative sample from the National Health and Nutrition Examination Survey 1999 to 2004.
A cross-sectional analysis of 2,134 women (546 pregnant) aged 20 to 40 without a history of CVD (cardiovascular disease) was performed.
The authors reported the following findings:
Among pregnant women in the first trimester, the prevalence of elevated NT-proBNP (>125 pg/mL) was 20.0% (SE, 6.6%) compared to 2.4% (SE, 0.8%) among women in the third trimester and 8.0% among nonpregnant women.
After adjustment for demographics and cardiovascular risk factors, NT-proBNP was 44% higher (absolute difference 26.4 pg/mL) in the first trimester of pregnancy compared to nonpregnant women.
Among pregnant women only, adjusted NT-proBNP was 46% lower (absolute difference −22.2 pg/mL) in women in the third trimester versus women in the first trimester.
NT-proBNP was inversely associated with body mass index and with systolic blood pressure.
"We found higher NT-proBNP levels in women in the pregnancy's first trimester compared with nonpregnant women and women in their later trimester," the researchers wrote. "Similarly, there was a higher prevalence of increased NT-proBNP in the first trimester versus nonpregnant women and those in late trimesters."
Across the second and third trimesters, systolic blood pressure and BMI were associated with lower NT-proBNP. The results suggest that NT-proBNP levels are dynamic throughout pregnancy and differ from nonpregnant women.
"Our findings indicate that NT-proBNP interpretation in pregnant women without CVD is complex," the researchers conclude. "BMI, trimester, and blood pressure may need to be considered for NT-proBNP assessment in pregnant women."
Reference:
Minhas, A. S., Rooney, M. R., Fang, M., Zhang, S., Ndumele, C. E., Tang, O., Schulman, S. P., Michos, E. D., McEvoy, J. W., Echouffo-Tcheugui, J., Christenson, R., & Selvin, E. (2023). Prevalence and Correlates of Elevated NT-proBNP in Pregnant Women in the General U.S. Population. JACC: Advances, 2(2), 100265. https://doi.org/10.1016/j.jacadv.2023.100265