Hemodynamic, ventilatory and gas exchange responses to exercise using a cycle ergometer and the incremental shuttle walk test in pregnant women.

BACKGROUND: Cardiovascular disease, including hypertension, in pregnant women is a leading cause of morbidity and mortality globally. The development of reference intervals for cardiovascular responses using exercising testing to measure oxygen utilisation (V̇O2) with cardiopulmonary exercise testing (CPET), and distances walked using the incremental shuttle walk test (ISWT), may be promising methods to assess and stratify pregnant women regarding their risk of adverse pregnancy outcomes, to encourage exercise during pregnancy, and to improve exercise prescriptions during pregnancy. We aimed to determine the reference intervals for V̇O2 at rest, anaerobic threshold (AT), and submaximal exercise using CPET, and the reference interval for the ISWT, to develop a correlation equitation that predicts submaximal V̇O2 from the distance walked in the ISWT, and to explore the relationship between hemoglobin (Hb) and ferritin concentration and V̇O2 at AT in women in second trimester. METHODS: After prospective IRB approval (HREC 15/23) and clinical trials registration (ANZCTR ACTRN12615000964516), and informed written consent, we conducted CPET and the ISWT according to international guidelines in a university associated tertiary referral obstetric and adult medicine hospital, in healthy pregnant women in second trimester (14 to 27 gestational weeks). Hemoglobin and ferritin concentrations were recorded from pathology results in the participants' medical records at the time of exercise testing. Adverse events were recorded. RESULTS: About 90 participants undertook CPET, 28 of which also completed the ISWT. The mean ± SD age and body mass index (BMI) were 32 ± 3.2 years, and 25 ± 2.7 kg/m2. Median (IQR) gestation was 23 (22-24) weeks. One in 4 women were 24 weeks or greater gestation. The reference intervals for V̇O2 at rest, AT, and submaximal exercise were 2.9 to 5.3, 8.1 to 20.7, and 14.1 to 30.5 mL/kg/min respectively. The reference interval for the ISWT was 218 to 1058 meters. The correlation equation to predict submaximal V̇O2 from the distance walked in the ISWT was submaximal V̇O2 (mL/kg/min) = 0.012*distance walked in ISWT (m) + 14.7 (95%CI slope 0.005-0.070, Pearson r = 0.5426 95%CI 0.2126-0.7615, P = .0029). Hemoglobin concentration was positively correlated with V̇O2 at AT (AT V̇O2 (mL/kg/min) = 0.08*Hb (g/L) + 4.9 (95%CI slope 0.0791-0.143, Pearson r = 0.2538 95%CI 0.049-0.438, P = .016). There was no linear association between ferritin and submaximal V̇O2 (Pearson r = 0.431 P = .697). There were no maternal or fetal complications. CONCLUSIONS: CPET and ISWT are safe and feasible in women in second trimester including those at or beyond 24 weeks gestation. We have established the reference interval for V̇O2 at rest, AT, and submaximal exercise by CPET, the reference interval for the distance walked for the ISWT, and a correlation equation to predict submaximal V̇O2 for use in clinical practice and research. Hemoglobin rather than ferritin is likely correlated with exercise capacity in pregnancy suggesting vigilance to correct lower hemoglobin levels may positively impact maternal health. CLINICAL TRIALS REGISTRY: The study was prospectively registered with the Australian and New Zealand Clinical Date of registration - 15/9/2015; Date of initial participant enrolment - 4/11/2015; Clinical trial identification number; ACTRN12615000964516; URL of the registration site - https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=369216.

Resting Hemodynamics and Response to Exercise Using the 6-Minute Walk Test in Late Pregnancy: An International Prospective Multicentre Study.

BACKGROUND: Cardiac disease is the leading cause of maternal death. Assessment of cardiovascular fitness is important in pregnant women because it is linked to increased risk of cardiac disease but is rarely undertaken or studied. The 6-Minute Walk Test (6MWT) is a safe exercise test but is not used in pregnancy. We determined the 95% reference interval for resting heart rate (HR) and distance walked for the 6MWT, as well as hemodynamic recovery variables, and quantified expectations and actual experiences of exertion and breathlessness with exercise in late pregnancy. METHODS: After institutional research board approval (Australian and New Zealand Clinical Trials Registry Number: 12615000964516), 300 healthy term nulliparous pregnant women performed the 6MWT at 3 tertiary referral obstetric hospitals using a standardized protocol. Each woman underwent two 6MWT with maximum 15-minute recovery period after each test. Hemodynamic variables were measured at rest and after exercise. Participants were asked 4 questions, 2 regarding expectation and 2 regarding actual experience, using the Rating of Perceived Exertion scale and Modified Borg Dyspnea scale. RESULTS: Participant characteristics and resting variables were mean (standard deviation [SD]); age, 31 years (4.2 years); body mass index, 27 kg/m (2.9 kg/m); gestational age, 37 weeks (1.3 weeks); HR, 85 bpm (10.8 bpm) with 95% reference interval 64-106 bpm; systolic blood pressure, 112 mm Hg (10.2 mm Hg); diastolic blood pressure, 72 mm Hg (8.6 mm Hg); oxygen saturation, 98% (0.9%); and respiratory rate, 18 breaths/min (5.7 breaths/min). The mean (SD) average distance walked was 488 m (94.9 m) with a speed of 3.0 mph (0.64 mph) with a 95% reference interval of 302-674 m. The mean (SD) HR increase with exercise was 12 bpm (11.0 bpm) with a median [quartile] recovery time of 5.0 minutes [1-8 minutes]. A lower resting HR was associated with increased distance walked (r = -0.207; 95% confidence interval, -0.313 to -0.096; P < .001). A greater HR change with exercise was associated with increased recovery time from exercise (r = 0.736; 95% confidence interval, 0.697-0.784; P < .001). Sixty-three percent and 83% of participants, respectively, expected to be more exerted and breathless than they actually were with exercise. CONCLUSIONS: The 6MWT is feasible and applicable in term pregnant women. The reference intervals for resting HR and distance walked in the 6MWT have been generated. HR increases by approximately 12 bpm with submaximal exercise, and half of the women recovered within 5 minutes of submaximal exercise. Women expected to be more exerted and breathless than they actually were with exercise.

Associations between maternal size and health outcomes for women undergoing caesarean section: a multicentre prospective observational study (The MUM SIZE Study).

OBJECTIVES: To investigate associations between maternal body mass index (BMI) at delivery (using pregnancy-specific BMI cut-off values 5 kg/m2 higher in each of the WHO groups) and clinical, theatre utilisation and health economic outcomes for women undergoing caesarean section (CS). DESIGN: A prospective multicentre observational study. SETTING: Seven secondary or tertiary referral obstetric hospitals. PARTICIPANTS: One thousand and four hundred and fifty-seven women undergoing all categories of CS. DATA COLLECTION: Height and weight were recorded at the initial antenatal visit and at delivery. We analysed the associations between delivery BMI (continuous and pregnancy-specific cut-off values) and total theatre time, surgical time, anaesthesia time, maternal and neonatal adverse outcomes, total hospital admission and theatre costs. RESULTS: Mean participant characteristics were: age 32 years, gestation at delivery 38.4 weeks and delivery BMI 32.2 kg/m2. Fifty-five per cent of participants were overweight, obese or super-obese using delivery pregnancy-specific BMI cut-off values. As BMI increased, total theatre time, surgical time and anaesthesia time increased. Super-obese participants had approximately 27% (17 min, p<0.001) longer total theatre time, 20% (9 min, p<0.001), longer surgical time and 40% (11 min, p<0.001) longer anaesthesia time when compared with normal BMI participants. Increased BMI at delivery was associated with increased risk of maternal intensive care unit admission (relative risk 1.07, p=0.045), but no increased risk of neonatal admission to higher acuity care. Total hospital admission costs were 15% higher in super-obese women compared with normal BMI women and theatre costs were 27% higher in super-obese women. CONCLUSIONS: Increased maternal BMI was associated with increased total theatre time, surgical and anaesthesia time, increased total hospital admission costs and theatre costs. Clinicians and health administrators should consider these clinical risks, time implications and financial costs when managing pregnant women.

Heart failure in pregnant women: is it peripartum cardiomyopathy?

Peripartum cardiomyopathy is a rare but important cause of maternal morbidity and mortality. Women with peripartum cardiomyopathy often present with symptoms and signs of heart failure. The diagnosis of peripartum cardiomyopathy is made after all other causes of heart failure are excluded. Emphasis is on the immediate recognition of an unwell pregnant or recently pregnant woman, early diagnosis with the use of echocardiography, and the correct treatment of heart failure.