Objectives Cardiopulmonary exercise testing (CPET) is a well-established investigation used to stratify operative and anaesthetic risk as well as being predictive of cardiovascular morbidity and mortality. Pregnancy is a biological stress test and we hypothesised that CPET could risk stratify women with cardio-respiratory or metabolic disease during pregnancy. However, normal values in normal pregnancy are required before the predictive value of this test can be assessed in women with cardio-respiratory disease. This pilot study was designed to test the feasibility and tolerability of performing combined CPET and exercise echocardiography during pregnancy.

Methods We prospectively recruited 10 women with a singleton pregnancy; all were healthy with no known medical conditions. Each participant attended at mean 14+1 (±2 days) (visit 1) and 24+5 (±3 days) (visit 2) weeks of gestation. At each visit participants had a resting echocardiogram, fetal ultrasound scan and baseline blood sample collected. A stepwise incrementing CPET was then performed with a maternal echocardiogram at maximal exertion. A blood sample was collected at maximal exertion.

Results The participants had a mean age at visit 1 of 35 years (±4), 6 were nulliparous, BMI was 24.3 (±3.3). Combined CPET and exercise echo was successfully completed in all participants. There was no significant difference between visits for resting mean arterial pressure: 86.7 mmHg (±9.6) at visit 1 and 86.5 mmHg (±8.1) at visit 2 (p = 0.95), but resting left ventricular (LV) end diastolic volume increased from 77.3 ml (±15.1) in visit 1 to 83.8 ml (±17.2) in visit 2 (p = 0.008).

Systolic function did not significantly change between visits, ejection fraction: 63.8% (±5.9) compared to 61.4% (±4.6) at visit 2 (p = 0.36). Diastolic function was not significantly altered.

During the CPET test the peak workload achieved was similar at both visits: 165 Watts (±35.7) in visit 1 and 170 Watts (±36.9) in visit 2 (p = 0.51) as was VO₂ max ml/Kg/min: 28.5 (±6.3) compared to 26.6 (±2.9) (p = 0.34). Respiratory exchange ratio (RER) increased significantly between visits: 1.05 (±0.05) compared to 1.11 (±0.05) at visit 2 (p = 0.01). Lactates collected increased from 1.1 mmol/L (range 0.9–1.7) before maximal exercise to 6.4 mmol/L (range 4.5–8.8) after in visit 1 (p < 0.001) and from 1.1 mmol/L (range 0.5–2.8) to 6.0 mmol/L (range 2.2–7.7) in visit 2 (p < 0.001).

All participants delivered healthy live neonates at term gestation, however 1 participant developed pregnancy induced hypertension and 2 developed preeclampsia.

Conclusions We successfully demonstrated combined exercise echo and CPET studies is well tolerated in pregnant women at 14 and 24 weeks gestation. We also demonstrated this combined test as a successful technique for capturing a wealth of metabolic and cardiac structural and functional data. Cardiac volumes increased between visits. RER increased which might suggest test familiarity.