Trimester-Specific Hemodynamic and Blood Volume Adaptations in Pregnancy: A Systematic Review of Normal and High-Risk Populations

Abstract

Pregnancy involves significant cardiovascular adaptations, including increased blood volume, cardiac output (CO), and reduced systemic vascular resistance (SVR), which are essential to support fetal development. While these changes are well established, the timing, magnitude, and variability across maternal risk profiles remain inconsistently reported. Objectives: To synthesize original research from 2015 to 2025 examining trimester-specific changes in maternal hemodynamic and blood volume, with a focus on both normal and high-risk pregnancies. Methods: Systematic searches were conducted in PubMed, Science Direct, Scopus, and Wiley Online Library. Inclusion criteria encompassed original English-language studies involving human pregnancies that assessed maternal blood volume or cardiovascular parameters using validated methods. Extracted data were synthesized across four domains: study characteristics, trimester-wise trends, methodology, and quality. Results: Nine studies met the inclusion criteria. Most reported a rise in CO and plasma volume from early to mid-pregnancy, alongside a reduction in SVR. In contrast, high-risk groups, including those with fetal growth restriction (FGR), preeclampsia (PE), and obesity, demonstrated impaired adaptation, marked by persistently high SVR and reduced stroke volume. Conclusions: It was concluded that trimester-specific hemodynamic adaptation is essential for healthy pregnancy progression. Deviations in high-risk populations may serve as early markers of complications. Incorporating non-invasive cardiovascular monitoring into routine prenatal care may improve risk stratification and outcomes.