BackgroundNormal pregnancy is associated with marked changes in haemodynamic function, however the influence and potential benefits of antenatal physical exercise at different stages of pregnancy and postpartum remain unclear. The aim of this study was therefore to characterise the influence of regular physical exercise on haemodynamic variables at different stages of pregnancy and also in the postpartum period.MethodsFifity healthy pregnant women were recruited and randomly assigned (2 × 2 × 2 design) to a land or water-based exercise group or a control group. Exercising groups attended weekly classes from the 20th week of pregnancy onwards. Haemodynamic assessments (heart rate, cardiac output, stroke volume, total peripheral resistance, systolic and diastolic blood pressure and end diastolic index) were performed using the Task Force haemodynamic monitor at 12–16, 26–28, 34–36 and 12 weeks following birth, during a protocol including postural manoeurvres (supine and standing) and light exercise.ResultsIn response to an acute bout of exercise in the postpartum period, stroke volume and end diastolic index were greater in the exercise group than the non-exercising control group (p = 0.041 and p = 0.028 respectively). Total peripheral resistance and diastolic blood pressure were also lower (p = 0.015 and p = 0.007, respectively) in the exercise group. Diastolic blood pressure was lower in the exercise group during the second trimester (p = 0.030).ConclusionsAntenatal exercise does not appear to substantially alter maternal physiology with advancing gestation, speculating that the already vast changes in maternal physiology mask the influences of antenatal exercise, however it does appear to result in an improvement in a woman’s haemodynamic function (enhanced ventricular ejection performance and reduced blood pressure) following the end of pregnancy.Trial registrationClinicalTrials.gov NCT02503995. Registered 20 July 2015.

The risk of new-onset arrhythmia during pregnancy is high, presumably relating to changes in both haemodynamic and cardiac autonomic function. The ability to non-invasively assess an individual's risk of developing arrhythmia during pregnancy would therefore be clinically significant. We aimed to quantify electrocardiographic temporal characteristics during the first trimester of pregnancy and to compare these with non-pregnant controls. Ninety-nine pregnant women and sixty-three non-pregnant women underwent non-invasive cardiovascular and haemodynamic assessment during a protocol consisting of various physiological states (postural manoeurvres, light exercise and metronomic breathing). Variables measured included stroke volume, cardiac output, heart rate, heart rate variability, QT and QT variability and QTVI (a measure of the variability of QT relative to that of RR). Heart rate (p < 0.0005, p < 0.0005, p < 0.0005) and cardiac output (p = 0.043, p < 0.0005, p < 0.0005) were greater in pregnant women in all physiological states (respectively for the supine position, light exercise and metronomic breathing state), whilst stroke volume was lower in pregnancy only during the supine position (p < 0.0005). QTe (Q wave onset to T wave end) and QTa (T wave apex) were significantly shortened (p < 0.05) and QTeVI and QTaVI were increased in pregnancy in all physiological states (p < 0.0005). QT variability (p < 0.002) was greater in pregnant women during the supine position, whilst heart rate variability was reduced in pregnancy in all states (p < 0.0005). Early pregnancy is associated with substantial changes in heart rate variability, reflecting a reduction in parasympathetic tone and an increase in sympathetic activity. QTVI shifted to a less favourable value, reflecting a greater than normal amount of QT variability. QTVI appears to be a useful method for quantifying changes in QT variability relative to RR (or heart rate) variability, being sensitive not only to physiological state but also to gestational age. We support the use of non-invasive markers of cardiac electrical variability to evaluate the risk of arrhythmic events in pregnancy, and we recommend the use of multiple physiological states during the assessment protocol.

Advancing gestation is associated with a shift in HRV/QTVI towards values that have been associated with an elevated risk of arrhythmia. A 20-week exercise programme undertaken between mid and late pregnancy exaggerated these changes during rest in the third trimester of pregnancy.

Weekly exercise exaggerated the reductions in BRS and HRV during pregnancy and is likely linked to diminished parasympathetic activity.

We share here our experience of recruiting pregnant women into an exercise intervention study. Recruitment challenges were anticipated owing to the study design, which required four hospital visits for cardiovascular assessment, a long-term (nine-month) commitment, and adherence to a 20-week exercise programme. Fifty-three women were assigned to one of three groups (no-exercise, land exercise or water exercise) using a 2 × 2 × 2 flexible randomisation design. Seven hundred forty-four women were screened at an antenatal clinic, of whom 501 were eligible to participate in the study. One hundred forty-five women were subsequently approached: 46 (32%) of whom agreed to participate, 42 (29%) were interested but then declined and 57 (39%) declined outright. Our study design helped recruit pregnant women as it allowed them some choice of group membership. We also noted that the participant-researcher relationship is important in reducing attrition. Our experience provides indications of likely recruitment and attrition rates for future randomised controlled trials of this type.