First-Trimester Normotension Is a Weak Indicator of Normal Maternal Cardiovascular Function

Area of Science:

• Cardiovascular Physiology in Pregnancy
• Maternal-Fetal Medicine
• Hypertensive Disorders of Pregnancy

Background:

• Mean arterial pressure is defined as the product of cardiac output (CO) and total vascular resistance (TPR).
• Cardiovascular imbalances may precede hypertension in early pregnancy, potentially indicating risks for adverse gestational outcomes.
• This study investigates CO-TPR dynamics in normotensive first-trimester pregnancies.

Purpose of the Study:

• To test the hypothesis that a CO-TPR imbalance in first-trimester normotensive pregnancies is associated with increased risks for adverse gestational outcomes.
• To evaluate the predictive value of CO and TPR measurements beyond standard blood pressure thresholds.
• To explore the utility of CO and TPR assessments in screening for gestational hypertensive disorders.

Main Methods:

• Automated blood pressure measurement combined with impedance cardiography for CO and TPR assessment (NICCOMO).
• First-trimester normotensive pregnant women were categorized into groups based on CO and TPR percentiles (normal, high CO, high TPR).
• Subgroups were compared across different blood pressure thresholds (140/90, 130/85, 130/80 mmHg); outcomes were classified post-birth.

Main Results:

• Women with high TPR, even at blood pressure <140/90 mmHg, showed significantly increased odds of developing gestational hypertension (OR 3.795), late-onset preeclampsia (OR 3.137), and having neonates small for gestational age (OR 1.780).
• These associations remained significant across different blood pressure thresholds.
• Normal CO and TPR were associated with lower risks for adverse outcomes compared to elevated TPR.

Conclusions:

• Cardiovascular imbalances, specifically elevated TPR, can be detected in normotensive women during the first trimester.
• These early imbalances are linked to a higher risk of adverse gestational outcomes, including gestational hypertension, preeclampsia, and fetal growth restriction.
• CO and TPR assessments are valuable adjuncts to blood pressure monitoring for identifying high-risk pregnancies and warrant further investigation in screening algorithms.