Impact of pregnancy and obesity on cardiorespiratory responses during weight-bearing exercise

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.

Can we hit prenatal depression and anxiety through HIIT? The effectiveness of online high intensity interval training in pregnant women during the COVID-19 pandemic: a randomized controlled trial

BACKGROUND

In recent years high intensity interval training (HIIT) has grown in popularity. However, it rarely represents training interventions in experimental studies in pregnant populations. Therefore, in this study we aimed to assess changes in depressive symptoms, fear of childbirth, fear of Covid-19 and quality of life after an 8-week supervised online HIIT program, compared to an educational (self-performed physical activity) program.

METHODS

We conducted a randomized control trial among 54 Caucasian women in uncomplicated, singleton pregnancy (age 32 ± 4 years, 22 ± 4 week of gestation; mean ± SD). There were 34 women in the experimental group, who participated in an 8-week high intensity interval training program (HIIT group). The comparative group was constituted of 20 pregnant women who attended 8-week educational program (EDU group).

RESULTS

The most important finding was that mental health improved somewhat in both groups after the intervention, but only the HIIT group improved statistically significantly. The positive trends in lowering the severity of depressive symptoms, fear of childbirth, and fear of Covid-19 were observed in both groups. However, the positive response to the intervention was stronger in the EDU group. As a secondary outcome, there was a significant decrease in cardiorespiratory fitness level in the EDU group, while the HIIT group maintained unchanged level of maximal oxygen uptake.

CONCLUSIONS

HIIT seems to be beneficial for women with uncomplicated pregnancies to maintain adequate quality of life and mental health. However, more research is needed to determine the effectiveness of prenatal HIIT in pregnant women in various psychological conditions.

TRIAL REGISTRATION

We conducted this study in Poland, in 2021. It was approved by the Bioethics Commission at the District Medical Chamber in Gdansk (KB-8/21). The full study protocol was registered in ClinicalTrials.gov (NCT05009433).

Impact of ageing and pregnancy on the minute ventilation/carbon dioxide production response to exercise

Ventilatory efficiency can be evaluated using the relationship between minute ventilation (V′_E) and the rate of CO₂ production (V′_CO2). In accordance with the modified alveolar ventilation equation, this relationship is determined by changes in dead space volume (V_D) and/or the arterial CO₂ tension (P_aCO2) equilibrium point. In this review, we summarise the physiological factors that may account for normative ageing and pregnancy induced increases in V′_E/V′_CO2 during exercise. Evidence suggests that age-related increases in V_D and pregnancy-related decreases in the P_aCO2 equilibrium point are mechanistically linked to the increased V′_E/V′_CO2 during exercise. Importantly, the resultant increase in V′_E/V′_CO2 (ratio or slope), with normal ageing or pregnancy, remains below the critical threshold for prognostic indication in cardiopulmonary disease, is not associated with increased risk of adverse health outcomes, and does not affect the respiratory system's ability to fulfil its primary role of eliminating CO₂ and maintaining arterial oxygen saturation during exercise.

The minute ventilation/carbon dioxide production response to exercise is elevated with advancing age and in healthy pregnancy due to increased dead space and lowering of the arterial partial pressure of carbon dioxide equilibrium point, respectively.https://bit.ly/2GJXm0o

The associations of pregnancy-related symptoms with health-related quality of life at midpregnancy: the PregnActive project

AIM

To analyze the associations between the wide range of pregnancy-related symptoms and health-related quality of life.

MATERIAL AND METHODS

A cross-sectional study was developed among 155 healthy low-risk pregnant women, aged 18-45 years, participated in the study at midpregnancy. Health-related quality of life and pregnancy symptoms were assessed using the Medical Outcome Study 36-item short form questionnaire and the Pregnancy Symptoms Inventory, respectively. Simple correlations, hierarchical linear regressions and standard multiple regressions were performed.

RESULTS

Significant correlations, after adjusting for sociodemographic and anthropometric characteristics, were found between five pregnancy-related symptoms and physical component of health-related quality of life and between thirteen pregnancy-related symptoms and mental component. However, when all pregnancy symptoms were entered simultaneously into a multiple regression model, back pain and shortness of breath on the physical components, and feeling depressed and anxiety on the mental component were the main explanatory factors of health-related quality of life.

CONCLUSION

Among the wide range of pregnancy-related symptoms, back pain, hip or pelvic pain, shortness of breath, and feeling depressed and anxiety are the main symptoms affecting the physical and the mental components of health-related quality of life, respectively. An early detection of the pregnancy-related symptoms that may affect health-related quality of life enables early interventions aimed at ameliorating their negative impact on health-related quality of life and daily living activities at midpregnancy.

The physiological effect of early pregnancy on a woman's response to a submaximal cardiopulmonary exercise test

Given all its systemic adaptive requirements, pregnancy shares several features with physical exercise. In this pilot study, we aimed to assess the physiological response to submaximal cardiopulmonary exercise testing (CPET) in early pregnancy. In 20 healthy, pregnant women (<13 weeks gestation) and 20 healthy, non-pregnant women, we performed a CPET with stationary cycling during a RAMP protocol until 70% of the estimated maximum heart rate (HR) of each participant. Hemodynamic and respiratory parameters were non-invasively monitored by impedance cardiography (PhysioFlow® ) and a breath-by-breath analyzer (OxyconTM ). To compare both groups, we used linear regression analysis, adjusted for age. We observed a similar response of stroke volume, cardiac output (CO) and HR to stationary cycling in pregnant and non-pregnant women, but a slightly lower 1-min recovery rate of CO (-3.9 [-5.5;-2.3] vs. -6.6 [-8.2;-5.1] L min-1  min-1 ; p = .058) and HR (-38 [-47; -28] vs. -53 [-62; -44] bpm/min; p = .065) in pregnant women. We also observed a larger increase in ventilation before the ventilatory threshold (+6.2 [5.4; 7.0] vs. +3.2 [2.4; 3.9] L min-1  min-1 ; p < .001), lower PET CO2 values at the ventilatory threshold (33 [31; 34] vs. 36 [34; 38] mmHg; p = .042) and a larger increase of breathing frequency after the ventilatory threshold (+4.6 [2.8; 6.4] vs. +0.6 [-1.1; 2.3] breaths min-1  min-1 ; p = .015) in pregnant women. In conclusion, we observed a slower hemodynamic recovery and an increased ventilatory response to exercise in early pregnancy.

Associations of 24-hours activity composition with adiposity and cardiorespiratory fitness: The PregnActive project

AIM

This study examined the associations of activity behaviors composition (sleep, sedentary time, light and moderate-to-vigorous physical activity) with adiposity and cardiorespiratory fitness, and how isotemporal reallocations of time between activity behaviors are associated with differences in adiposity and cardiorespiratory fitness.

METHODS

A cross-sectional study was conducted in 130 women during midpregnancy. Activity behaviors, conceptualized as a 24-hours composition, were objectively assessed by multi-sensor monitors. Skinfold thickness, fat mass index, and body mass index were calculated as indicators of adiposity. Cardiorespiratory fitness was assessed using a 6-minute walk test. Log-ratio multiple linear regression models and compositional isotemporal substitutions were used to analyze the associations and estimated differences in outcomes.

RESULTS

The activity composition was significantly associated with adiposity indicators (all P < .001) and cardiorespiratory fitness (P values from .025 to <.001) during midpregnancy. The isotemporal substitutions were asymmetrical, showing the highest estimated differences in adiposity (8.7%, 0.80 kg/m² , for fat mass index; 6.0%, 2.65 mm, for the sum of skinfold thickness; and 3.8%, 1.02 kg/m² , for body mass index) and cardiorespiratory fitness (3.0%, 1.00 mL/kg min) when 30 minutes of moderate-to-vigorous physical activity was reallocated by sedentary time.

CONCLUSION

The activity composition was associated with adiposity and the cardiorespiratory fitness levels during midpregnancy, with moderate-to-vigorous physical activity being the leading activity behavior. The most unfavorable differences in adiposity and cardiorespiratory fitness were found when moderate-to-vigorous physical activity was replaced by another behavior, mainly sedentary time, reinforcing the importance of at least maintaining moderate-to-vigorous physical activity during pregnancy.

Explanatory factors and levels of health-related quality of life among healthy pregnant women at midpregnancy: A cross-sectional study of The PregnActive Project

AIMS

To identify potential explanatory factors and establish health-related quality of life (HRQoL) levels of healthy pregnant women at midpregnancy.

BACKGROUND

The HRQoL levels perceived by pregnant women are lower than those perceived by women of similar age and decline during the course of pregnancy.

DESIGN

An exploratory cross-sectional design was used.

METHODS

One hundred thirty-four healthy women from antenatal clinics completed questionnaires were administered a cardiorespiratory fitness (CRF) test and wore a multisensor body monitor for 7 days at midpregnancy. Data were collected from September 2015-December 2016.

RESULTS

Cardiorespiratory fitness, musculoskeletal symptoms, and age were identified as explanatory factors of the physical component summary of HRQoL. Explanatory factors of the mental component summary included musculoskeletal and psychological symptoms and light activity. Significant differences in HRQoL levels were identified among groups of pregnant women stratified by age, occupational status, pregnancy symptoms, and CRF.

CONCLUSIONS

Modifiable factors of HRQoL, such as CRF and active lifestyle may be important areas to target in interventions aimed at promoting HRQoL in healthy women at midpregnancy. The identification of the groups of pregnant women with lower levels of HRQoL may help midwives and health professional to focus their advice and conduct interventions on these groups of pregnant women. These modifiable factors should be considered in future longitudinal studies to determine causal effects, will likely help improve multidisciplinary treatments.

Maternal Responses to Aerobic Exercise in Pregnancy

Exercise is one of the most physiologically challenging stressors requiring the coordination of metabolic, respiratory, and cardiovascular responses to meet increased energy requirements of the working muscle. During pregnancy, all women without contraindication are encouraged to exercise as part of a healthy lifestyle. Pregnancy itself is associated with profound physiological adaptations to the maternal cardiovascular, respiratory, and metabolic systems, which serve to support the needs of the growing fetus. Therefore the physiological adaptations to exercise during pregnancy are more pronounced and critically important. This review provides an overview of our current understanding of the physiological adaptations to acute prenatal exercise.

Influences of prior miscarriage and weight status on perinatal psychological well-being, exercise motivation and behavior

OBJECTIVES

women who have experienced miscarriage may be at increased risk for elevated depressive and anxiety symptoms in subsequent pregnancies. Exercise may be a useful strategy for coping with these symptoms. Little is known about how miscarriage influences prenatal exercise behavior. The study purpose was to examine the influences of miscarriage history and prepregnancy weight status on pregnant women's psychological health, exercise motivation, and behavior using the Theory of Planned Behavior.

PARTICIPANTS/SETTING

Pregnant women (N=203; 41 with prior miscarriage; 72 overweight/obese; BMI > 25.0) in the northeast United States.

DESIGN

Women prospectively reported their depressive/anxiety symptoms and exercise motivation/behavior in the 1st, 2nd, and 3rd trimesters via mailed surveys. Group differences in depressive/anxiety symptoms, exercise behavior, and its motivational determinants were examined using Chi Square analyses and Univariate and Multivariate Analyses of Covariance.

MEASUREMENTS AND FINDINGS

Women with a history of miscarriage had higher 1st and 2nd trimester depressive/anxiety symptoms and lower 1st trimester attitudes about exercise and 1st and 2nd trimester perceived behavior control than women without a history of miscarriage. Overweight/obese women had higher 1st and 2nd trimester pregnancy depressive/anxiety symptoms, engaged in less prepregnancy exercise, and had lower levels of exercise intention, attitude, and perceived behavior control throughout pregnancy than normal weight women.

KEY CONCLUSIONS

Women with a history of miscarriage and overweight/obese women have poorer psychological health and lower motivation to exercise during pregnancy than women without a history of miscarriage and normal weight women.

IMPLICATIONS FOR PRACTITIONERS

Interventions and healthcare provider communications aimed at promoting perinatal exercise behavior and psychological health should take into account pre-pregnancy weight status and pregnancy history to identify strategies to help women, particularly overweight/obese women with a history of miscarriage, to overcome exercise barriers.

Cardiac Physiology of Pregnancy

Although the physiology of the heart and vascular system has not changed, there are many things we have learned and are still learning today. Research related to heart adaptations during pregnancy has been performed since the 1930s. Since the mid-1950s, researchers began to look at changes in the maternal cardiovascular system during exercise while pregnant. Research related to exercise during pregnancy and offspring heart development began and has continued since the 1970s. We will review the normal female cardiovascular system adaptations to pregnancy in general. Additionally, topics related to maternal cardiac adaptations to pregnancy during acute exercise, as well as the chronic conditioning response from exercise training will be explored. Since physical activity during pregnancy influences fetal development, the fetal cardiac development will be discussed in regards to acute and chronic maternal exercise. Similarly, the influence of various types of maternal exercise on acute and chronic fetal heart responses will be described. Briefly, the topics related to how and if there is maternal-fetal synchrony will be explained. Lastly, the developmental changes of the fetal cardiovascular system that persist after birth will be explored. Overall, the article will discuss maternal cardiac physiology related to changes with normal pregnancy, and exercise during pregnancy, as well as fetal cardiac physiology related to changes with normal development, and exercise during pregnancy as well as developmental changes in offspring after birth.

Fetal and maternal cardiac responses to physical activity and exercise during pregnancy

Since the 1970s, researchers have studied the influence of exercise during pregnancy on offspring heart development. With the knowledge and current evidence of fetal programming effects, research has demonstrated that exercise is safe and beneficial for mother, fetus, and neonate. Predominantly, research has focused on maternal and fetal cardiac adaptations related to aerobic exercise during pregnancy; less is known regarding the effects of resistance or combination (aerobic and resistance) training during pregnancy. Ongoing research is focusing on fetal responses to different intensity, duration and modes of maternal exercise throughout pregnancy. This article will summarize our current state of knowledge regarding the influence of exercise intensity, duration, and modes during pregnancy on maternal and fetal cardiac responses.

[Physical exercise, weight gain, and perinatal outcomes in overweight and obese pregnant women: a systematic review of clinical trials]

This study aimed to evaluate the effects of exercise on weight gain and perinatal outcomes among overweight and obese pregnant women, through a systematic review in MEDLINE/PubMed, EMBASE, LILACS, and SciELO. We included ten clinical trials that evaluated the effectiveness of exercise with or without combined diet in the control of gestational weight gain. Three studies were randomized, and methodological quality was assessed using the CONSORT 2010 Checklist, but none met all the criteria. Four studies showed weight gain differences between groups. The majority (60%) of studies showed no differences in perinatal outcomes (mode of delivery, gestational age at birth, birth weight). In conclusion, few studies confirmed the positive effect of exercise in controlling weight gain during pregnancy, thus requiring more research in this direction. Regarding perinatal outcomes, mild to moderate exercise does not appear to be decisive for perinatal outcomes, and is safe for pregnant women with overweight and obesity.

Exercise prescription for overweight and obese women: pregnancy and postpartum

Once a low-risk pregnancy has been established, walking in combination with nutritional control may be effective in preventing excessive weight gain in overweight and obese women. Maternal exercise prescription should use the Frequency, Intensity, Time spent and Type of exercise principle, with a frequency of three to four sessions per week as ideal. Intensity based on a target heart-rate zone of 110 to 131 beats per minute for women 20 to 29 years of age and 108 to 127 beats per minute for women 30 to 39 years of age, coupled with use of the rating of perceived exertion scale and the "Talk Test" is suggested. Dieting and exercise together are most effective in reducing weight retention after childbirth and compliance may be improved by incorporating child-care and children into the exercise routine. After medical consultation, postpartum women should begin exercise slowly, starting from 15 minutes, and building to at least 150 minutes of aerobic activity per week, with this activity spread throughout the week.