Slow Deep Breathing Boosts Heart Rhythms in Pregnant Women as Much as in Non-Pregnant Women

Slow and deep breathing has long been promoted as a natural way to lower blood pressure, but a new study suggests that the technique works just as powerfully in pregnant women as it does in women who are not pregnant. Researchers at Bournemouth University in the United Kingdom measured the acute cardiovascular responses of 41 women to a range of slow breathing frequencies and found that, despite the profound physiological changes of pregnancy, the maternal cardiovascular system responds to slow and deep breathing in remarkably similar ways to that of non-pregnant women.

The study, published in Frontiers in Network Physiology, comes at a time when gestational hypertension remains one of the most common complications of pregnancy, affecting up to 15 percent of expectant mothers. Defined as high blood pressure that appears after 20 weeks of gestation in women whose blood pressure was previously normal, gestational hypertension raises the risk of obstetric complications and, currently, the only definitive cure is delivery. Because many pregnant women are reluctant to take medication, non-pharmacological interventions such as slow and deep breathing have attracted growing interest as potential adjunctive treatments.

Slow and deep breathing is already recommended by the American Heart Association as an adjunctive therapy for hypertension in the general population, and recent meta-analyses have reported reductions of up to 5.26 mmHg in systolic blood pressure and 2.97 mmHg in diastolic blood pressure following daily practice. Yet pregnancy introduces a unique set of cardiovascular adaptations, including elevated heart rate, stroke volume and cardiac output, as well as an upward displacement of the diaphragm by as much as 5 centimetres, which could theoretically limit the effectiveness of deep breathing exercises. Whether these changes alter the acute response to slow breathing had never been systematically tested until now.

To answer this question, the research team recruited 23 healthy non-pregnant women and 18 healthy pregnant women, all of reproductive age and all normotensive at the time of testing. The pregnant participants, who were all carrying singleton pregnancies and had never given birth before, were more than 20 weeks into gestation, with an average gestational age of just over 31 weeks. Each participant completed five different breathing conditions in a randomised order, each lasting five minutes: spontaneous breathing, a dynamic slow breathing frequency guided by a bespoke optimisation algorithm, and three fixed frequencies of 4, 6 and 8 breaths per minute.

Throughout each condition, the researchers continuously monitored respired airflow with a pneumotachograph, heart rate with a three-lead electrocardiogram, and beat-to-beat arterial blood pressure using finger photoplethysmography. They also derived stroke volume, cardiac output, total peripheral resistance and pulse wave velocity from the recorded signals. Rather than relying solely on average values, the team adopted a Network Physiology approach, analysing the oscillations in cardiovascular variables both within and between breath phases, which allowed them to capture the dynamic coupling between the respiratory, cardiac and vascular systems.

The results revealed that slow and deep breathing dramatically amplified respiratory sinus arrhythmia, the natural variation in heart rate that occurs with each breath. The maximum amplitude of this rhythm during slow breathing was 2.1 times higher than during spontaneous breathing for both groups, peaking at 6 breaths per minute. Although pregnant women had significantly lower absolute respiratory sinus arrhythmia during spontaneous breathing, measuring just 0.07 seconds compared with 0.12 seconds in non-pregnant women, slow breathing increased their values to a level comparable to what non-pregnant women achieved at rest. In relative terms, the response was almost identical, with a maximum increase of roughly 48 percent in non-pregnant women and 47 percent in pregnant women.

Blood pressure oscillations told a similar story. In both groups, the amplitude of systolic and diastolic blood pressure fluctuations increased as breathing frequency declined, reaching a peak at 4 breaths per minute, where oscillations were up to 4.5 times higher, or about 10 mmHg, than during spontaneous breathing. When expressed as a percentage of mean blood pressure, there were no significant differences between pregnant and non-pregnant women in any slow breathing condition. The researchers also observed that stroke volume and cardiac output oscillations were significantly greater during slow breathing, while total peripheral resistance oscillations increased in both groups, painting a picture of a coordinated multi-system response rather than isolated changes in individual variables.

One of the most striking findings concerned the choice of breathing frequency. When asked which condition they would prefer to practise daily until birth, 55 percent of pregnant participants chose 6 breaths per minute, and a further 22 percent ranked it as a close second choice, giving a total of 78 percent who favoured this frequency. There was no correlation between preferred frequency and gestational age, suggesting that all slow breathing frequencies remain manageable throughout pregnancy. The researchers also noted that 8 breaths per minute may be too fast to elicit the full cardiovascular response, as many variables showed no significant difference between this frequency and spontaneous breathing.

The implications of these findings extend beyond the laboratory. Because attenuated respiratory sinus arrhythmia has been proposed as a biophysical marker of pre-eclampsia, and because it reflects the functional state of the autonomic nervous system, the ability of slow breathing to restore this rhythm to pre-pregnancy levels is promising. The authors suggest that if blood pressure oscillations underpin the anti-hypertensive effect of slow breathing, these oscillations can be amplified in pregnant women at frequencies between 4 and 6 breaths per minute. They recommend that future interventions targeting gestational hypertension should use 6 breaths per minute, which optimises both physiological responses and participant comfort.

The study is not without limitations. All haemodynamic measurements were non-invasive and therefore estimates of true values, although the Modelflow method used to derive stroke volume has previously shown excellent agreement with Doppler ultrasound. The sample size was also relatively small, particularly for subgroup analyses across gestational age, and menstrual cycle phase or oral contraceptive use was not recorded for the non-pregnant participants. Nevertheless, the researchers emphasise that their work provides essential baseline data before moving on to test slow breathing in women who actually develop gestational hypertension, and they call for future studies to examine whether daily practice of slow breathing can produce long-term changes in blood pressure, respiratory sinus arrhythmia and other cardiovascular variables in pregnant populations.

Subject of Research: Cardiovascular responses to slow and deep breathing in pregnant and non-pregnant women

Article Title: Acute cardiovascular responses to slow and deep breathing in normotensive non-pregnant and pregnant women

Article References: Felton, M., Grigsby, S., & Hundley, V. A. (2026). Acute cardiovascular responses to slow and deep breathing in normotensive non-pregnant and pregnant women. Frontiers in Network Physiology, 6, Article 1913383. https://doi.org/10.3389/fnetp.2026.1913383

Image Credits: AI Generated

DOI: 10.3389/fnetp.2026.1913383

Keywords: slow breathing, pregnancy, blood pressure, respiratory sinus arrhythmia, gestational hypertension, network physiology, cardiovascular health, Acute, cardiovascular, responses, slow, deep