ABC | Volume 114, Nº4, April 2020

Original Article Linhares et al. Hydrotherapy reduces arterial stiffness in pregnant women Arq Bras Cardiol. 2020; 114(4):647-654 Table 1 – Characteristics of the control (CG) and hypertensive (HG) groups Variables Entire sample Control Hypertensive (n = 12) p (n = 36) (n = 24) Age (years) 30.4 ± 4.8 30.5 ± 5.1 30 ± 4.3 0.741 T BMI (kg/m 2 ) 31.7 ± 7.3 28.1 ± 4.7 38.9 ± 6 < 0.001 T Race 0.719 F White 13 (36.1%) 8 (33.3%) 5 (41.7%) Black 23 (63.9%) 16 (66%) 7 (58.3%) Practice physical activity 8 (22.2%) 7 (29.2%) 1 (8.3%) 0.224 F Use of medications 29 (80.6%) 17 (70.8%) 12 (100%) 0.070 F Methyldopa 12 (41.4%) - 12 (100%) - Multivitamin 11 (37.9%) 9 (52.9%) 2 (16.7%) 0.064 F Iron sulfate 6 (20.7%) 5 (29.4%) 1 (8.3%) 0.354 F Folic acid 4 (13.8%) 3 (17.6%) 1 (8.3%) 0.622 F Gestational age (weeks) 29.2 ± 3.3 29.3 ± 3.3 29 ± 3.5 0.840 T Note: The p values refer to Student's t test (T) for independent samples and Fisher's exact test (F) . BMI: body mass index. Hydrotherapy promoted a significant reduction in AIx@75 in both groups, with percentage differences of 22.2% in the HG (p = 0.024) and 21.3% in the CG (p = 0.001), as shown in Figure 1. There was also a significant reduction in HR, with differences of 11 bpm (p < 0.001) in the HG and 9.9 bpm (p < 0.001) in the CG (Figure 2a). There was a trend toward a decrease in SBP after the hydrotherapy session, which was not significant (p = 0.050) (Figure 2b). There was no significant difference between the measurements obtained before and after the intervention for the other variables evaluated (Table 2). In a comparison between the groups, higher values were observed in the HG compared with the CG regarding SBP, DBP, MAP, PP, central SBP, and PWV, both before and after the intervention (Table 2). However, there were no differences between groups in AIx@75 and HR values, which were variables that decreased significantly with the intervention. No adverse events or discomforts associated with the hydrotherapy sessions were reported by the pregnant women evaluated. Discussion This study evaluated the impact of a hydrotherapy session on AS in high-risk pregnant women with CH compared with normal-risk pregnant women, yielding evidence unprecedented in the literature. Despite concerns about the safety of aquatic exercises during pregnancy, the procedure in our study proved to be safe for pregnant women with hypertension and controls in the third trimester of pregnancy. Barakat et al. 26 also demonstrated the safety of exercise practice among pregnant women. These authors compared the effects of exercise on pregnant women, concluding that while land exercises were more effective at preventing maternal weight gain, aquatic or combined programs involving land and water were more effective at preventing gestational diabetes. 26 Bacchi et al., 27 evaluating 100 healthy pregnant women, concluded that three weekly sessions of aquatic activities during pregnancy prevent maternal overweight and preserve birth weight. A meta-analysis concluded that a single isolated aerobic exercise session lasting 10 to 50 minutes at different intensities could reduce SBP by 5 to 7 mmHg, an effect that is maintained for up to 24 hours after training. 28 The magnitude of this reduction in SBP is comparable to the effect of most preferred antihypertensive drugs, 29 which presupposes a reduction in cardiovascular risk of 20 to 30%, 30 according to the conclusion of the position stand of the American College of Sports Medicine on exercise and hypertension. 31 In our study, we observed that hydrotherapy promoted a 6% reduction in SBP (139.6 ± 12.1 mmHg/130.1 ± 12.6 mmHg, p = 0.050) in the HG, a percentage similar to that described for other aerobic modalities but without a significant difference, probably due to the small sample size. The BP variation in a liquid medium is considered to be predominantly affected by three components: temperature, immersion depth, and exercises during hydrotherapy. 32,33-35 Small changes in water temperature have significant effects on heat loss or retention in the immersed patient because water has a thermal conductivity 25 times higher than air. 35 Additionally, the vasodilating effects of contact with heated water are well established. 36 The temperature of the water has a significant influence on maternal and fetal hemodynamics, and temperatures above 38.9 o C have even been shown to cause potential embryonic or fetal deleterious effects. 37 Despite using different parameters regarding the temperature of the water, duration, and level of immersion, there are reports of decreased BP induced by immersion. 38-40 Immersion causes reflex cardiovascular adjustments, such as redistribution of body fluids due to hydrostatic pressure, which leads to increased central blood volume, decreased HR, and increased systolic volume, cardiac output and natriuresis. 35 649