Hormonal responses to exercise in diabetic and nondiabetic pregnant patients

Glucose responses to acute and chronic exercise during pregnancy: a systematic review and meta-analysis

Objective

To perform a systematic review and meta-analysis to explore the relationship between prenatal exercise and glycaemic control.

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 and reviews) if they were 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 acute or chronic exercise, alone (‘exercise-only’) or in combination with other intervention components (eg, dietary; ‘exercise+cointervention’) at any stage of pregnancy), comparator (no exercise or different frequency, intensity, duration, volume and type of exercise) and outcome (glycaemic control).

Results

A total of 58 studies (n=8699) were included. There was ‘very low’ quality evidence showing that an acute bout of exercise was associated with a decrease in maternal blood glucose from before to during exercise (6 studies, n=123; mean difference (MD) −0.94 mmol/L, 95% CI −1.18 to −0.70, I2=41%) and following exercise (n=333; MD −0.57 mmol/L, 95% CI −0.72 to −0.41, I2=72%). Subgroup analysis showed that there were larger decreases in blood glucose following acute exercise in women with diabetes (n=26; MD −1.42, 95% CI −1.69 to −1.16, I2=8%) compared with those without diabetes (n=285; MD −0.46, 95% CI −0.60 to −0.32, I2=62%). Finally, chronic exercise-only interventions reduced fasting blood glucose compared with no exercise postintervention in women with diabetes (2 studies, n=70; MD −2.76, 95% CI −3.18 to −2.34, I2=52%; ‘low’ quality of evidence), but not in those without diabetes (9 studies, n=2174; MD −0.05, 95% CI −0.16 to 0.05, I2=79%).

Conclusion

Acute and chronic prenatal exercise reduced maternal circulating blood glucose concentrations, with a larger effect in women with diabetes.

Care of diabetes in pregnancy

Diabetes, whether existing before pregnancy or brought on by changes in maternal physiology, poses risks to the mother and developing fetus. Excellent preconceptional and pregnancy care can help to minimize, or even to eliminate, these risks. This article reviews the problems that are associated with diabetes in pregnancy and evidence-based strategies to avoid them.

Gestational diabetes and exercise: a survey

Exercise has long been accepted as an adjunctive nonmedical intervention in the management of diabetes in nonpregnant subjects. It is universally accepted that pregnancy is a diabetogenic event which could develop into gestational diabetes mellitus (GDM) in up to 12% of pregnant women. GDM, a carbohydrate intolerance of variable severity with onset or first recognition during pregnancy, involves a relative resistance to insulin. Exercise becomes thus a logical intervention, only recently offered as an adjunctive therapy to pregnant diabetics. This article reviews our current understanding of the role of exercise in the management of GDM.

Metabolic and hormonal responses to low-impact aerobic dance during pregnancy

This study examined the plasma glucose, free fatty acids (NEFA), lactate, triglyceride, cortisol, and insulin responses of pregnant women (22-28 wk) to a 40-min aerobic dance program and 40-min treadmill walking at similar heart rate intensities. The heart rates during exercise averaged 135 +/- 5 bt.min-1 for both trials. Immediate post-exercise plasma glucose levels were lower than resting levels for both exercise trials (P < 0.05), and remained below resting levels 20 min after exercise. Plasma triglycerides and NEFA were increased immediately post-exercise (P < 0.05), and returned toward rest 20 min after exercise. The NEFA responses at the end of the walking trials were significantly greater than at the end of the aerobic dance trials (P < 0.05). For both trials, immediate post-exercise plasma insulin levels were below resting levels (P < 0.05) and remained attenuated 20 min post-exercise. Plasma cortisol concentrations were unchanged throughout the aerobic dance trial. However, a mean increase of 105 nmol.l-1 immediately post-exercise was evident during the walking trials (P < 0.05). The results suggest that 40 min of walking or aerobic dance reduces blood glucose but does not cause hypoglycemia. Further, the results suggest that 40 min of walking or aerobic dance does not expose the mother to serious metabolic consequences that might adversely affect the fetus.

A comparison of cardiopulmonary adaptations to exercise in pregnancy at sea level and altitude

OBJECTIVE

The purpose of this study was to compare maternal cardiopulmonary and fetal responses of lowlander pregnant women in the third trimester to exercise at sea level and at an altitude of 6000 feet.

STUDY DESIGN

Seven women at 33.86 +/- 1 weeks' gestation performed a symptom-limited maximal exercise test and a submaximal cardiac output exercise test at sea level at an altitude of 6000 feet. Cardiopulmonary and metabolic variables were measured and compared at sea level and altitude.

RESULTS

Maximal oxygen consumption and work levels were limited by short-term altitude exposure. Ventilatory variables were not significantly influenced by altitude exposure. During submaximal exercise no alteration in exercise efficiency or response was seen for most of the variables when altitude and sea level data were compared. Both cardiac output and stroke volume were elevated at altitude at rest but not during exercise, suggesting a lower reserve for both variables at altitude. Level of plasma glucose, lactate, norepinephrine, and epinephrine were not significantly influenced by altitude exposure. Fetal heart rate responses did not differ between the sea level and altitude conditions.

CONDITIONS

Lowlander pregnant women in the third trimester have some limitations to maximal aerobic capacity but not submaximal exercise on short-term altitude exposure. No ominous fetal responses have been observed during this study. The results suggest that pregnant women may engage in at least brief moderate exercise bouts at moderate altitude without adverse consequences.

Therapeutic exercise for insulin-requiring gestational diabetics: effects on the fetus--results of a randomized prospective longitudinal study

Regular physical activity is an established therapeutic adjunct in diabetes, but has not been offered to pregnant diabetics in the past; for sports might induce significant cardiovascular and hormonal changes that are able to reduce blood flow to the uterus and thus limit oxygen transfer to the fetus. Studying the impact of a medically supervised exercise program on gestational diabetes mellitus [GDM) in a randomised prospective longitudinal study, this paper aims to assess the effects of maternal moderate and strenuous exercise on the fetus. By evaluating shortterm fetal responses as reflected in heart rate patterns (FHR) and longterm-pregnancy complications and neonatal outcome, our results suggest that--in absence of ominous FHR changes or significant changes in uterine activity following the exercise sessions or increased diabetes-related peri- and neonatal morbidity--regular physical activity seems to be a safe therapeutic option for the fetus of GDM mothers.

Physical and glycemic responses of women with gestational diabetes to a moderately intense exercise program

Aerobic exercise machines are becoming more popular. Their use by women with gestational diabetes is reported, and their benefits in improving blood glucose management and in increasing maternal fitness without undue stress to the fetus are substantiated. Of equal benefit is the use of an exercise specialist to prescribe an individual exercise program, to increase the safety and effectiveness of the workout, to monitor maternal and fetal well-being, to record relevant data, and to provide feedback and information to the patient about the exercise session. The use of exercise specialists in the clinical setting should prove a useful adjunct to medical and dietary regimens for the woman with gestational diabetes.

Exercise prescription in pregnancy: weight-bearing versus non-weight-bearing exercise

Bicycle ergometry (non-weight-bearing exercise) and treadmill (weight-bearing exercise) were compared to assess physiologic responses to similar work loads. A total of 22 subjects at 29.3 +/- 1.6 (+/- SEM) weeks' gestation who performed non-weight-bearing exercise were compared with 15 similarly fit subjects at 26.1 +/- 2.3 weeks' gestation who performed weight-bearing exercise at three submaximal levels. Measurements by indirect calorimetry indicate preferential carbohydrate use during non-weight-bearing exercise at submaximal levels.