Abstract
Given all its systemic adaptive requirements, pregnancy shares several features with physical exercise. In this pilot study, we aimed to assess the physiological response to submaximal cardiopulmonary exercise testing (CPET) in early pregnancy. In 20 healthy, pregnant women (<13 weeks gestation) and 20 healthy, non‐pregnant women, we performed a CPET with stationary cycling during a RAMP protocol until 70% of the estimated maximum heart rate (HR) of each participant. Hemodynamic and respiratory parameters were non‐invasively monitored by impedance cardiography (PhysioFlow®) and a breath‐by‐breath analyzer (OxyconTM). To compare both groups, we used linear regression analysis, adjusted for age. We observed a similar response of stroke volume, cardiac output (CO) and HR to stationary cycling in pregnant and non‐pregnant women, but a slightly lower 1‐min recovery rate of CO (−3.9 [−5.5;‐2.3] vs. −6.6 [−8.2;‐5.1] L min−1 min−1; p = .058) and HR (−38 [−47; −28] vs. −53 [−62; −44] bpm/min; p = .065) in pregnant women. We also observed a larger increase in ventilation before the ventilatory threshold (+6.2 [5.4; 7.0] vs. +3.2 [2.4; 3.9] L min−1 min−1; p < .001), lower PETCO2 values at the ventilatory threshold (33 [31; 34] vs. 36 [34; 38] mmHg; p = .042) and a larger increase of breathing frequency after the ventilatory threshold (+4.6 [2.8; 6.4] vs. +0.6 [−1.1; 2.3] breaths min−1 min−1; p = .015) in pregnant women. In conclusion, we observed a slower hemodynamic recovery and an increased ventilatory response to exercise in early pregnancy.
Highlights
Human pregnancy initiates essential physiological changes in the mother in order to meet the increased demands of the growing placenta and fetus
oxygen consumption (VO2) was 13.4 [95% confidence intervals (CI) 11.6;15.1] ml kg−1 min−1 in the pregnant women versus 17.6 [95% CI 15.9;19.2] ml kg−1 min−1 in the non-pregnant women; p = .010), there were no differences in means of VE, VO2 and carbon dioxide production (VCO2) between groups (Table 3a; Figure 3)
This study confirms that women who are in their first trimester of pregnancy already have an altered response to exercise compared to non-pregnant women
Summary
Human pregnancy initiates essential physiological changes in the mother in order to meet the increased demands of the growing placenta and fetus. Almost all maternal organ systems require such changes, including the cardiovascular, gastrointestinal, renal, and respiratory systems. These changes start very early in pregnancy. Pulmonary adaptation to pregnancy starts in the first weeks of pregnancy, with a rise in resting minute ventilation (VE) up to 20%–50% at term compared to the non-pregnant state (Clapp et al, 1988; Hegewald & Crapo, 2011). It is thought that, in women who develop placenta-related pregnancy complications, such as preeclampsia and fetal growth restriction, an increased risk for cardiovascular disease is unmasked by the stressed state of pregnancy (Bamfo et al, 2008; Barker & Thornburg, 2013; Sattar & Greer, 2002)
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