The influence of high maternal body mass index (≥35 kg/m²) on haemodynamic parameters during pregnancy: a prospective observational study

Maternal obesity is a growing global health concern, yet its impact on maternal haemodynamic throughout pregnancy remains underexplored. We investigated haemodynamic adaptations across gestation in women with high body mass index (BMI) (≥35 kg/m²) and results were compared to low-risk controls (BMI 18.5–24.9 kg/m²). This prospective observational study used non-invasive cardiac output monitoring (NICOM; Baxter Healthcare, Deerfield, IL) to assess maternal haemodynamic parameters, including cardiac output (CO), stroke volume (SV), total peripheral resistance (TPR), systolic blood pressure (sBP) and mean arterial pressure (MAP) in pregnant women with high BMI. Assessments were carried out across five gestational windows (11–19 + 6, 20–27 + 6, 28–33 + 6, 34–37 + 6 and ≥38 weeks). Results were compared to low-risk healthy controls (BMI 18.5–24.9 kg/m²). A total of 329 women were recruited, including 125 with high BMI and 189 controls. Across all gestational windows, women with high BMI consistently demonstrated significantly higher CO and SV. Compared to controls, median CO was high among women with high BMI, at 11–19 + 6 weeks [8.8 L/min (IQR 7.2–9.9) versus 6.7 L/min (5.8–7.6); <i>p</i> &lt; .001]; median SV was 104.2 mL (93.7–124.9) versus 81.9 mL (74.3–94.0) (<i>p</i> &lt; .001). This trend persisted at later gestations. In contrast, median TPR was significantly lower in the high BMI group; at 28–33 + 6 weeks, 847 dyn·s·cm⁻⁵ (unit of measurement of TPR: dynes·seconds per centimetre to the fifth power) (783–937) versus 1083 (924–1161) in the controls (<i>p</i> &lt; .001). Despite reduced TPR, sBP and MAP were higher in women with high BMI throughout pregnancy. Heart rate (HR) and diastolic blood pressure (dBP) did not differ significantly between groups at any gestational window. Pregnant women with high BMI have a distinctive haemodynamic profile characterised by high CO with a compensatory reduction in TPR. Further research is required to assess the risk of placental mediated diseases in that group. Maternal obesity affects a growing number of pregnancies, but its impact on maternal heart function and blood flow throughout pregnancy is not fully understood. In our study, we measured heart function in pregnant women with high body mass index (BMI ≥35 kg/m²) and compared these results to healthy women with normal BMI. Women with high BMI had stronger heart output and greater blood volume during pregnancy. Despite having lower resistance in their blood vessels, these women also had higher blood pressure. These findings highlight important cardiovascular changes linked to obesity in pregnancy, suggesting that specialised monitoring could improve health outcomes for these women and their babies.孕产妇肥胖已成为日益严峻的全球公共健康问题，但其对整个妊娠周期内孕产妇血流动力学（haemodynamic）的影响仍未得到充分探索。本研究针对身体质量指数（BMI，body mass index）≥35 kg/m²的妊娠女性，探究其整个妊娠阶段的血流动力学适应性变化，并将结果与低风险对照组（BMI 18.5~24.9 kg/m²）进行对比。本项前瞻性观察研究采用非侵入性心输出量监测系统（NICOM；百特医疗（Baxter Healthcare），美国伊利诺伊州迪尔菲尔德市），对高BMI妊娠女性的多项血流动力学参数进行评估，包括心输出量（CO，cardiac output）、每搏输出量（SV，stroke volume）、总外周阻力（TPR，total peripheral resistance）、收缩压（sBP，systolic blood pressure）及平均动脉压（MAP，mean arterial pressure）。评估共覆盖5个妊娠孕周评估窗口：11~19+6周、20~27+6周、28~33+6周、34~37+6周及≥38周，并将结果与健康低风险对照组（BMI 18.5~24.9 kg/m²）进行比较。本研究共招募329名女性，其中高BMI组125名，对照组189名。在所有妊娠孕周评估窗口中，高BMI组女性的心输出量与每搏输出量均持续显著升高。以11~19+6周为例，高BMI组的中位心输出量为8.8 L/min（四分位数间距IQR：7.2~9.9），对照组为6.7 L/min（IQR：5.8~7.6）（P<0.001）；中位每搏输出量分别为104.2 mL（IQR：93.7~124.9）与81.9 mL（IQR：74.3~94.0）（P<0.001）。该趋势在妊娠晚期同样持续存在。与之相反，高BMI组的总外周阻力显著降低：以28~33+6周为例，高BMI组中位总外周阻力为847 dyn·s·cm⁻⁵（达因·秒·厘米⁻⁵，IQR：783~937），对照组为1083 dyn·s·cm⁻⁵（IQR：924~1161）（P<0.001）。尽管总外周阻力降低，高BMI组妊娠女性在整个妊娠周期内的收缩压与平均动脉压均更高。而心率（HR，heart rate）与舒张压（dBP，diastolic blood pressure）在各妊娠阶段的组间差异均无统计学意义。高BMI妊娠女性具有独特的血流动力学特征，表现为心输出量升高，同时伴随总外周阻力的代偿性降低。后续仍需开展进一步研究，以评估该群体发生胎盘介导疾病（placental mediated diseases）的风险。孕产妇肥胖影响的妊娠数量日益增多，但其对整个妊娠周期内孕产妇心脏功能与血流的影响尚未完全明确。本研究对高BMI（BMI≥35 kg/m²）妊娠女性的心脏功能进行了检测，并将结果与BMI正常的健康女性进行对比。高BMI女性在妊娠期间的心输出量更高、血容量更大。尽管其血管阻力更低，但该群体的血压水平却更高。本研究结果揭示了妊娠期间肥胖相关的重要心血管变化，提示采用针对性监测手段可改善该群体母婴的健康结局。