The effect of maternal exercise on fetal umbilical artery waveforms

Maternal and Fetal Cardiovascular Responses to Acute High-Intensity Interval and Moderate-Intensity Continuous Training Exercise During Pregnancy: A Randomized Crossover Trial

OBJECTIVE

We aimed to compare maternal and fetal cardiovascular responses to an acute bout of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) during pregnancy.

METHODS

Fifteen women with a singleton pregnancy (27.3 ± 3.5 weeks of gestation, 33 ± 4 years of age) were recruited. Following a peak fitness test, participants engaged in a session of HIIT (10 × 1-min intervals ≥ 90% maximum heart rate [HRmax]) interspersed with 1 min of active recovery) and MICT (30 min at 64-76% HRmax) 48 h apart in random order. Maternal HR, blood pressure, middle (MCAv), and posterior cerebral artery blood velocity (PCAv), as well as respiratory measures were monitored continuously throughout HIIT/MICT. Fetal heart rate, as well as umbilical systolic/diastolic (S/D) ratio, resistive index (RI), and pulsatility index (PI) were assessed immediately before and after exercise.

RESULTS

Average maternal heart rate was higher for HIIT (82 ± 5% HRmax) compared with MICT (74 ± 4% HRmax; p < 0.001). During the HIIT session, participants achieved a peak heart rate of 96 ± 5% HRmax (range of 87-105% HRmax). Maternal cerebral blood velocities increased with exercise but was not different between HIIT and MICT for MCAv (p = 0.340) and PCAv (p = 0.142). Fetal heart rate increased during exercise (p = 0.244) but was not different between sessions (HIIT: Δ + 14 ± 7 bpm; MICT: Δ + 10 ± 10 bpm). Metrics of umbilical blood flow decreased with exercise and were not different between exercise sessions (PI: p = 0.707; S/D ratio: p = 0.671; RI: p = 0.792). Fetal bradycardia was not observed, and S/D ratio, RI, and PI remained within normal ranges both before and immediately after all exercise sessions.

CONCLUSIONS

An acute bout of HIIT exercise consisting of repeated 1-min near-maximal to maximal exertions, as well as MICT exercise is well tolerated by both mother and fetus.

CLINICAL TRIAL REGISTRATION

NCT05369247.

Moderate intensity exercise in pregnant patients with cardiovascular disease: A pilot study

BACKGROUND

Exercise in pregnancy has proven health benefits, yet the safety of exercise in patients with pre-existing cardiovascular disease (CVD) has not been established. Our aim was to determine the feasibility and safety profile of moderate intensity exercise during pregnancy in patients with CVD, compared with those without CVD.

METHODS

This is a prospective single center pilot study of a moderate intensity exercise regimen, with data collection through wearable fitness trackers and personal exercise logs in pregnant patients with and without pre-existing CVD. The primary outcome was Doppler umbilical artery systolic to diastolic (S/D) ratio measured between 32 and 34 weeks' gestation. The secondary outcomes were adverse maternal and fetal events, trends in wearable fitness tracker data, C-reactive protein levels, and weight changes.

RESULTS

At baseline, the CVD group (62% congenital heart disease) took part in more prepregnancy walking, less weightlifting, and had a higher body mass index compared to the control group, and on average walked 539 fewer steps per day during pregnancy than the control group. Resting heart rate (HR) was found to increase in both groups up to 30 weeks' gestation. The cardiovascular disease group displayed an overall lower exercise intensity, as measured by the ability to increase HR with exercise over resting heart rate 1 hour prior to exercise at study baseline (45% vs 59% P < .001). Umbilical artery S/D ratio was normal in both groups. No differences were seen in adverse events between groups.

CONCLUSIONS

This pilot study of moderate intensity exercise in pregnant individuals with pre-existing CVD demonstrated that patients with CVD were not able to increase their HR during exercise throughout pregnancy compared to those in the control group. Although a small study group, this data supports the hypothesis that exercise interventions during pregnancy for patients with CVD are feasible without evidence abnormal fetal Doppler profiles. Further studies using wearable fitness trackers may provide the opportunity to understand how to safely tailor exercise programs to pregnant individuals with CVD.

Assessment of physical fitness during pregnancy: validity and reliability of fitness tests, and relationship with maternal and neonatal health - a systematic review

Objectives

To systematically review studies evaluating one or more components of physical fitness (PF) in pregnant women, to answer two research questions: (1) What tests have been employed to assess PF in pregnant women? and (2) What is the validity and reliability of these tests and their relationship with maternal and neonatal health?

Design

A systematic review.

Data sources

PubMed and Web of Science.

Eligibility criteria

Original English or Spanish full-text articles in a group of healthy pregnant women which at least one component of PF was assessed (field based or laboratory tests).

Results

A total of 149 articles containing a sum of 191 fitness tests were included. Among the 191 fitness tests, 99 (ie, 52%) assessed cardiorespiratory fitness through 75 different protocols, 28 (15%) assessed muscular fitness through 16 different protocols, 14 (7%) assessed flexibility through 13 different protocols, 45 (24%) assessed balance through 40 different protocols, 2 assessed speed with the same protocol and 3 were multidimensional tests using one protocol. A total of 19 articles with 23 tests (13%) assessed either validity (n=4), reliability (n=6) or the relationship of PF with maternal and neonatal health (n=16).

Conclusion

Physical fitness has been assessed through a wide variety of protocols, mostly lacking validity and reliability data, and no consensus exists on the most suitable fitness tests to be performed during pregnancy.

PROSPERO registration number

CRD42018117554.

Impact of maternal physical activity during an uncomplicated pregnancy on fetal and neonatal well-being parameters: a systematic review of the literature

We carried a thorough systematic review of the contemporary literature regarding the impact of maternal physical activity during pregnancy on the fetal and neonatal well-being parameters. We searched systematically publications indexed in PubMed and ScienceDirect, according to the PRISMA protocol. Studies examining following fetal and neonatal well-being parameters were included: fetal heart rate, active fetal movements, Doppler assessment of the placental and fetal circulations, amniotic fluid index, Apgar score, and umbilical cord blood acid-basis analysis at delivery. Altogether, 73 studies were identified (pooled sample size n = 7867). Out of these, 42 pertained to acute and 31 pertained to chronic exposure to maternal physical activity. The majority of the identified studies reported a positive or neutral effect of maternal physical activity on the fetal heart rate, Doppler-derived umbilical and cerebral blood flow parameters, and Apgar score. The literature regarding uterine arteries Doppler assessment, fetal active movements, amniotic fluid index, and umbilical cord blood acid-base analysis at delivery is sparse and does not allow us to generalize the inferences. Maternal physical activity during physiological pregnancy is safe for fetal and neonatal well-being when practiced according to recommendations. There is a need for better quality studies concerning the subject.

Spotlight on the fetus: how physical activity during pregnancy influences fetal health: a narrative review

Before and during pregnancy, women often aim to improve their lifestyle so as to provide a healthier environment for their developing child. It remains unresolved, however, as to whether physical activity (PA) during pregnancy poses a possible risk or whether it might even have beneficial effects on the developing child. There is increasing evidence that PA during pregnancy is indeed beneficial to maternal physiological and psychological health and that it is generally not detrimental to the fetal cardiovascular system and neuronal function in the developing child. This also led to international recommendations for PAs during pregnancy. In the current review, we aimed to comprehensively assess the evidence of beneficial and harmful effects of maternal PA, including high-performance sports, on fetal development. The different mental and body-based relaxation techniques presented here are frequently performed during pregnancy. We found a considerable number of studies addressing these issues. In general, neither low key, moderate maternal PA nor relaxation techniques were observed to have a harmful effect on the developing child. However, we identified some forms of PA which could have at least a transient unfavourable effect. Notably, the literature currently available does not provide enough evidence to enable us to make a general conclusive statement on this subject. This is due to the lack of longitudinal studies on the metabolic and cognitive effects of regular PA during pregnancy and the wide diversity of methods used. In particular, the kind of PA investigated in each study differed from study to study.

Effects of prenatal exercise on fetal heart rate, umbilical and uterine blood flow: a systematic review and meta-analysis

OBJECTIVE

To perform a systematic review and meta-analysis examining the influence of acute and chronic prenatal exercise on fetal heart rate (FHR) and umbilical and uterine blood flow metrics.

DESIGN

Systematic review with random-effects meta-analysis and meta-regression.

DATA SOURCES

Online databases were searched up to 6 January 2017.

STUDY ELIGIBILITY CRITERIA

Studies of all designs were included (except case studies) if published in English, Spanish or French, and contained information on the population (pregnant women without contraindication to exercise), intervention (subjective or objective measures of frequency, intensity, duration, volume or type of exercise, alone ["exercise-only"] or in combination with other intervention components [eg, dietary; "exercise + co-intervention"]), comparator (no exercise or different frequency, intensity, duration, volume and type of exercise) and outcomes (FHR, beats per minute (bpm); uterine and umbilical blood flow metrics (systolic:diastolic (S/D) ratio; Pulsatility Index (PI); Resistance Index (RI); blood flow, mL/min; and blood velocity, cm/s)).

RESULTS

'Very low' to 'moderate' quality evidence from 91 unique studies (n=4641 women) were included. Overall, FHR increased during (mean difference (MD)=6.35bpm; 95% CI 2.30 to 10.41, I²=95%, p=0.002) and following acute exercise (MD=4.05; 95% CI 2.98 to 5.12, I²=83%, p<0.00001). The incidence of fetal bradycardia was low at rest and unchanged with acute exercise. There were no significant changes in umbilical or uterine S/D, PI, RI, blood flow or blood velocity during or following acute exercise sessions. Chronic exercise decreased resting FHR and the umbilical artery S/D, PI and RI at rest.

CONCLUSION

Acute and chronic prenatal exercise do not adversely impact FHR or uteroplacental blood flow metrics.

Effect of maternal exercises on biophysical fetal and maternal parameters: a transversal study

Objective

To evaluate the acute effects of maternal and fetal hemodynamic responses in pregnant women submitted to fetal Doppler and an aerobic physical exercise test according to the degree of effort during the activity and the impact on the well-being.

Methods

Transversal study with low risk pregnant women, obtained by convenience sample with gestational age between 26 to 34 weeks. The participants carry out a progressive exercise test.

Results

After the exercise session, reduced resistance (p=0.02) and pulsatility indices (p=0.01) were identified in the umbilical artery; however, other Doppler parameters analyzed, in addition to cardiotocography and fetal biophysical profile did not achieve significant change. Maternal parameters obtained linear growth with activity, but it was not possible to establish a standard with the Borg scale, and oxygen saturation remained stable.

Conclusion

A short submaximal exercise had little effect on placental blood flow after exercise in pregnancies without complications, corroborating that healthy fetus maintains homeostasis even in situations that alter maternal hemodynamics.

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.

Strenuous exercise during pregnancy: is there a limit?

OBJECTIVE

The purpose of this study was to evaluate fetal responses to strenuous exercise in physically active and inactive women.

STUDY DESIGN

Forty-five healthy women (15 who were nonexercisers, 15 who were regularly active, 15 who were highly active) underwent a peak treadmill test at 28 weeks' gestation to 32 weeks 6 days' gestation. Fetal well-being (umbilical artery Doppler indices, fetal heart tracing/rate, biophysical profile [BPP]) was evaluated before and after exercise. Uterine artery Doppler scans were also obtained.

RESULTS

Umbilical and uterine artery Doppler indices were similar among activity groups and did not change with exercise (P > .05). BPP and fetal heart tracings were reassuring in all groups. However, subgroup analyses showed transient fetal heart rate decelerations after exercise and elevated umbilical and uterine artery Doppler indices in 5 highly active women. After this, BPP and fetal heart tracings were reassuring.

CONCLUSION

Overall fetal well-being is reassuring after short-duration, strenuous exercise in both active and inactive pregnant women. A subset of highly active women experienced transient fetal heart rate decelerations and Doppler changes immediately after exercise. Athletes may push beyond a threshold intensity at which fetal well-being may be compromised. However, potential impact on neonatal outcomes is unknown.

Exercise during pregnancy: fetal responses to current public health guidelines

OBJECTIVE

To evaluate acute fetal responses to individually prescribed exercise according to existing guidelines (U.S. Department of Health and Human Services) in active and inactive pregnant women.

METHODS

Forty-five healthy pregnant women (15 nonexercisers, 15 regularly active, 15 highly active) were tested between 28 0/7 and 32 6/7 weeks of gestation. After a treadmill test to volitional fatigue, target heart rates were calculated for two subsequent 30-minute treadmill sessions: 1) moderate intensity (40-59% heart rate reserve); and 2) vigorous intensity (60-84%). All women performed the moderate test; only active women performed the vigorous test. Fetal well-being measures included umbilical artery Dopplers, fetal heart tracing and rate, and biophysical profile. Measures were obtained at rest and immediately postexercise.

RESULTS

Groups were similar in age, body mass index, and gestational age. Maternal resting heart rate in the highly active group (61.6 ± 7.2 beats per minute [bpm]) was significantly lower than the nonexercise (79.0 ± 11.6 bpm) and regularly active (71.9 ± 7.4 bpm) groups (P<.001). Treadmill time was longer in highly active (22.3 ± 2.9 minutes) than regularly active (16.6 ± 3.4) and nonexercise (12.1 ± 3.6) groups (P<.001), reflecting higher fitness. With moderate exercise, all umbilical artery Doppler indices were similar pre-exercise and postexercise among groups. With vigorous exercise, Dopplers were similar in regularly and highly active women with statistically significant decreases postexercise (P<.05). The group × time interaction was not significant. Postexercise fetal heart tracings met criteria for reactivity within 20 minutes after all tests. Biophysical profile scores were reassuring.

CONCLUSION

This study supports existing guidelines indicating pregnant women may begin or maintain an exercise program at moderate (inactive) or vigorous (active) intensities.

The effect of maternal exercise on uterine artery velocimetry waveforms

One hundred and two subjects in the second half of pregnancy were subject to an acute exercise test lasting 5 minutes on an upright bicycle ergometer. The pulsatility index (using Doppler ultrasound) of the right uterine artery was analysed before exercise and at 2, 4, 6, 8, 10, 12, 16, 20, 24 and 30 minutes after exercise. The mean exercise intensity achieved was 67.2% of sub-maximal exercise (range 51-90%). At 2 minutes post-exercise, the mean uterine artery pulsatility index was increased from the baseline value, reaching a maximum of 0.64 at 8 minutes (baseline 0.583). After 8 minutes there was a gradual decrease in the pulsatility index, and at 24 and 30 minutes the values were significantly lower (P < 0.001 and P < 0.001 respectively). Smokers had significantly higher pulsatility index values than non-smokers (P < 0.004). Primigravidae also had lower resistance indices compared with multigravidae (P < 0.001). We conclude that exercise in the second half of pregnancy appears to cause a transient increase in the maternal uterine artery pulsatility index. We also believe that at this level of exercise intensity there was no evidence of harmful effects on maternal uterine blood flow.

Doppler examinations of fetal and uteroplacental blood flow in AGA and IUGR fetuses before and after maternal physical exercise with the bicycle ergometer

OBJECTIVE

To study changes in uteroplacental and fetal circulation after maternal exercise in appropriate-for-gestational-age fetuses (AGA) and intrauterine-growth-retarded fetuses (IUGR).

MATERIALS AND METHOD

33 women with an uncomplicated course of pregnancy and ten women with IUGR were examined. Physical stress was caused through a bicycle ergometer with 1.25 W/kg maternal weight. Doppler examinations were performed in the umbilical artery, fetal aorta, middle cerebral and in the uterine artery. Fetal heart rate was documented by monitoring. Maternal lactate and glucose levels as well as maternal blood pressure and heart rate were recorded.

RESULTS

No significant changes after cycling could be observed in umbilical and uterine vessels either in the normal pregnancies or in pregnancies with IUGR. In contrast, in the fetal aorta an increase of the RI was recorded in both groups (an increase of 16% [P<0.01] and 18% [P<0.05], respectively for AGA and IUGR cases). In cerebral arteries a decrease of the RI was observed after cycling in both groups (a decrease of 24% [P<0.01] and 13% [P<0.05], respectively for AGA and IUGR cases). In AGA fetuses the RI of the aorta and middle cerebral artery returned to pre-test level by the 18th minute of examination. In IUGR fetuses the RI of the aorta and middle cerebral artery did not return to pre-test levels at the end of the test. Fetal heart rate remained unchanged in both groups. Maternal blood pressure and heart rate increased during the exertion phase but returned to initial values at the end of the test. A 21% and 24% (for AGA and IUGR groups respectively) reduction of maternal glucose values after exercise was observed (P<0.001). Lactate values doubled in both groups after exercise (P<0.001).

CONCLUSION

From the results obtained we conclude that maternal exercise does not significantly alter uterine and umbilical perfusion in AGA and IUGR pregnancies, suggesting an absence of change in the uterine vascular bed resistance. However, submaximal maternal exercise was followed by fetal cerebral vasodilatation and an increase of resistance in the fetal aorta that was more evident in IUGR fetuses. This might be due to slight fetal hemoglobin desaturation in those cases.

Effect of maternal exercise on fetal umbilical artery waveforms: the comparison of IUGR and AFD fetuses

OBJECTIVE

To determine the effect of maternal exercise on the fetal blood flow of normal and growth-retarded fetuses.

METHODS

The effect of maternal exercise on fetal blood flow was investigated with 24 pregnant women between 36 and 42 weeks' gestation. Seventeen pregnancies were uncomplicated (normal group) and the other 7 were complicated with growth-retarded fetuses (IUGR group). They underwent graded walking on a treadmill with an upper limit of 150 bpm for the maternal heart rate. The systolic over diastolic velocity ratio (S/D ratio) of the umbilical artery was measured before exercise, and at 3, 5, 10, and 15 minutes after exercise.

RESULTS

The mean S/D ratio of the IUGR group before exercise was significantly higher than that of the normal group (p < 0.05). The S/D ratio did not change significantly after exercise, in either the normal group or the IUGR group.

CONCLUSION

This study suggests that maternal exercise at this level of intensity and duration does not have any harmful effect, even on growth-retarded fetuses that might have placental dysfunctions.