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.

Is supine exercise associated with adverse maternal and fetal outcomes? A systematic review.

OBJECTIVE: Theoretical concerns regarding the supine position at rest due to the gravid uterus obstructing aorta and vena caval flow may impinge uterine blood flow (UBF) to the fetus and maternal venous return. DESIGN: Systematic review. DATA SOURCES: Online databases up to 11 December 2017. STUDY CRITERIA: Eligible population (pregnant without contraindication to exercise), intervention (frequency, intensity, duration, volume or type of supine exercise), comparator (no exercise or exercise in left lateral rest position, upright posture or other supine exercise), outcomes (potentially adverse effects on maternal blood pressure, cardiac output, heart rate, oxygen saturation, fetal movements, UBF, fetal heart rate (FHR) patterns; adverse events such as bradycardia, low birth weight, intrauterine growth restriction, perinatal mortality and other adverse events as documented by study authors), and study design (except case studies and reviews) published in English, Spanish, French or Portuguese. RESULTS: Seven studies (n=1759) were included. 'Very low' to 'low' quality evidence from three randomised controlled trials indicated no association between supervised exercise interventions that included supine exercise and low birth weight compared with no exercise. There was 'very low' to 'low' quality evidence from four observational studies that showed no adverse events in the mother; however, there were abnormal FHR patterns (as defined by study authors) in 20 of 65 (31%) fetuses during an acute bout of supine exercise. UBF decreased (13%) when women moved from left lateral rest to acute dynamic supine exercise. CONCLUSION: There was insufficient evidence to ascertain whether maternal exercise in the supine position is safe or should be avoided during pregnancy.

Exercise for the prevention and treatment of low back, pelvic girdle and lumbopelvic pain during pregnancy: a systematic review and meta-analysis.

OBJECTIVE: The purpose of this review was to investigate the relationship between prenatal exercise, and low back (LBP), pelvic girdle (PGP) and lumbopelvic (LBPP) pain. 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 eligible (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 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 outcome (prevalence and symptom severity of LBP, PGP and LBPP). RESULTS: The analyses included data from 32 studies (n=52 297 pregnant women). 'Very low' to 'moderate' quality evidence from 13 randomised controlled trials (RCTs) showed prenatal exercise did not reduce the odds of suffering from LBP, PGP and LBPP either in pregnancy or the postpartum period. However, 'very low' to 'moderate' quality evidence from 15 RCTs identified lower pain severity during pregnancy and the early postpartum period in women who exercised during pregnancy (standardised mean difference -1.03, 95% CI -1.58, -0.48) compared with those who did not exercise. These findings were supported by 'very low' quality evidence from other study designs. CONCLUSION: Compared with not exercising, prenatal exercise decreased the severity of LBP, PGP or LBPP during and following pregnancy but did not decrease the odds of any of these conditions at any time point.

Prenatal exercise is not associated with fetal mortality: a systematic review and meta-analysis.

OBJECTIVE: To perform a systematic review of the relationship between prenatal exercise and fetal or newborn death. 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 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 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 outcome (miscarriage or perinatal mortality). RESULTS: Forty-six studies (n=2 66 778) were included. There was 'very low' quality evidence suggesting no increased odds of miscarriage (23 studies, n=7125 women; OR 0.88, 95% CI 0.63 to 1.21, I2=0%) or perinatal mortality (13 studies, n=6837 women, OR 0.86, 95% CI 0.49 to 1.52, I2=0%) in pregnant women who exercised compared with those who did not. Stratification by subgroups did not affect odds of miscarriage or perinatal mortality. The meta-regressions identified no associations between volume, intensity or frequency of exercise and fetal or newborn death. As the majority of included studies examined the impact of moderate intensity exercise to a maximum duration of 60 min, we cannot comment on the effect of longer periods of exercise. SUMMARY/CONCLUSIONS: Although the evidence in this field is of 'very low' quality, it suggests that prenatal exercise is not associated with increased odds of miscarriage or perinatal mortality. In plain terms, this suggests that generally speaking exercise is 'safe' with respect to miscarriage and perinatal mortality.

Effects of prenatal exercise on incidence of congenital anomalies and hyperthermia: a systematic review and meta-analysis.

OBJECTIVE: To investigate the relationships between exercise and incidence of congenital anomalies and hyperthermia. DESIGN: Systematic review with random-effects meta-analysis . DATA SOURCES: Online databases were searched from inception up to 6 January 2017. STUDY ELIGIBILITY CRITERIA: Studies of all designs were eligible (except case studies and reviews) if they were published in English, Spanish or French, and contained information on 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 [e.g., dietary; "exercise + co-intervention"]), comparator (no exercise or different frequency, intensity, duration, volume or type of exercise) and outcome (maternal temperature and fetal anomalies). RESULTS: This systematic review and meta-analysis included 'very low' quality evidence from 14 studies (n=78 735) reporting on prenatal exercise and the odds of congenital anomalies, and 'very low' to 'low' quality evidence from 15 studies (n=447) reporting on maternal temperature response to prenatal exercise. Prenatal exercise did not increase the odds of congenital anomalies (OR 1.23, 95% CI 0.77 to 1.95, I2=0%). A small but significant increase in maternal temperature was observed from pre-exercise to both during and immediately after exercise (during: 0.26°C, 95% CI 0.12 to 0.40, I2=70%; following: 0.24°C, 95% CI 0.17 to 0.31, I2=47%). SUMMARY/CONCLUSIONS: These data suggest that moderate-to-vigorous prenatal exercise does not induce hyperthermia or increase the odds of congenital anomalies. However, exercise responses were investigated in most studies after 12 weeks' gestation when the risk of de novo congenital anomalies is negligible.

Impact of prenatal exercise on maternal harms, labour and delivery outcomes: a systematic review and meta-analysis.

OBJECTIVE: To perform a systematic review of the relationships between prenatal exercise and maternal harms including labour/delivery outcomes. DESIGN: Systematic review with random effects meta-analysis and meta-regression. DATASOURCES: Online databases were searched up to 6 January 2017. STUDY ELIGIBILITY CRITERIA: Studies of all designs were included (except case studies) 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 exercise), comparator (no exercise or different frequency, intensity, duration, volume and type of exercise, alone ["exercise-only"] or in combination with other intervention components [e.g., dietary; "exercise + co-intervention"]) and outcome (preterm/prelabour rupture of membranes, caesarean section, instrumental delivery, induction of labour, length of labour, vaginal tears, fatigue, injury, musculoskeletal trauma, maternal harms (author defined) and diastasis recti). RESULTS: 113 studies (n=52 858 women) were included. 'Moderate' quality evidence from exercise-only randomised controlled trials (RCTs) indicated a 24% reduction in the odds of instrumental delivery in women who exercised compared with women who did not (20 RCTs, n=3819; OR 0.76, 95% CI 0.63 to 0.92, I 2= 0 %). The remaining outcomes were not associated with exercise. Results from meta-regression did not identify a dose-response relationship between frequency, intensity, duration or volume of exercise and labour and delivery outcomes. SUMMARY/CONCLUSIONS: Prenatal exercise reduced the odds of instrumental delivery in the general obstetrical population. There was no relationship between prenatal exercise and preterm/prelabour rupture of membranes, caesarean section, induction of labour, length of labour, vaginal tears, fatigue, injury, musculoskeletal trauma, maternal harms and diastasis recti.

2019 Canadian guideline for physical activity throughout pregnancy.

The objective is to provide guidance for pregnant women and obstetric care and exercise professionals on prenatal physical activity. The outcomes evaluated were maternal, fetal or neonatal morbidity, or fetal mortality during and following pregnancy. Literature was retrieved through searches of MEDLINE, EMBASE, PsycINFO, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Scopus and Web of Science Core Collection, CINAHL Plus with Full Text, Child Development & Adolescent Studies, Education Resources Information Center, SPORTDiscus, ClinicalTrials.gov and the Trip Database from inception up to 6 January 2017. Primary studies of any design were eligible, except case studies. Results were limited to English-language, Spanish-language or French-language materials. Articles related to maternal physical activity during pregnancy reporting on maternal, fetal or neonatal morbidity, or fetal mortality were eligible for inclusion. The quality of evidence was rated using the Grading of Recommendations Assessment, Development and Evaluation methodology. The Guidelines Consensus Panel solicited feedback from end users (obstetric care providers, exercise professionals, researchers, policy organisations, and pregnant and postpartum women). The development of these guidelines followed the Appraisal of Guidelines for Research and Evaluation II instrument. The benefits of prenatal physical activity are moderate and no harms were identified; therefore, the difference between desirable and undesirable consequences (net benefit) is expected to be moderate. The majority of stakeholders and end users indicated that following these recommendations would be feasible, acceptable and equitable. Following these recommendations is likely to require minimal resources from both individual and health systems perspectives.

Effectiveness of exercise interventions in the prevention of excessive gestational weight gain and postpartum weight retention: a systematic review and meta-analysis.

OBJECTIVE: Gestational weight gain (GWG) has been identified as a critical modifier of maternal and fetal health. This systematic review and meta-analysis aimed to examine the relationship between prenatal exercise, GWG and postpartum weight retention (PPWR). DESIGN: Systematic review with random effects meta-analysis and meta-regression. Online databases were searched up to 6 January 2017. STUDY ELIGIBILITY CRITERIA: Studies of all designs in English, Spanish or French were eligible (except case studies and reviews) if they contained information on the population (pregnant women without contraindication to exercise), intervention (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 or type of exercise) and outcomes (GWG, excessive GWG (EGWG), inadequate GWG (IGWG) or PPWR). RESULTS: Eighty-four unique studies (n=21 530) were included. 'Low' to 'moderate' quality evidence from randomised controlled trials (RCTs) showed that exercise-only interventions decreased total GWG (n=5819; -0.9 kg, 95% CI -1.23 to -0.57 kg, I2=52%) and PPWR (n=420; -0.92 kg, 95% CI -1.84 to 0.00 kg, I2=0%) and reduced the odds of EGWG (n=3519; OR 0.68, 95% CI 0.57 to 0.80, I2=12%) compared with no exercise. 'High' quality evidence indicated higher odds of IGWG with prenatal exercise-only (n=1628; OR 1.32, 95% CI 1.04 to 1.67, I2=0%) compared with no exercise. CONCLUSIONS: Prenatal exercise reduced the odds of EGWG and PPWR but increased the risk of IGWG. However, the latter result should be interpreted with caution because it was based on a limited number of studies (five RCTs).

Prenatal exercise for the prevention of gestational diabetes mellitus and hypertensive disorders of pregnancy: a systematic review and meta-analysis.

OBJECTIVE: Gestational diabetes mellitus (GDM), gestational hypertension (GH) and pre-eclampsia (PE) are associated with short and long-term health issues for mother and child; prevention of these complications is critically important. This study aimed to perform a systematic review and meta-analysis of the relationships between prenatal exercise and GDM, GH and PE. 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 [e.g., dietary; "exercise + co-intervention"]), Comparator (no exercise or different frequency, intensity, duration, volume and type of exercise) and Outcomes (GDM, GH, PE). RESULTS: A total of 106 studies (n=273 182) were included. 'Moderate' to 'high'-quality evidence from randomised controlled trials revealed that exercise-only interventions, but not exercise+cointerventions, reduced odds of GDM (n=6934; OR 0.62, 95% CI 0.52 to 0.75), GH (n=5316; OR 0.61, 95% CI 0.43 to 0.85) and PE (n=3322; OR 0.59, 95% CI 0.37 to 0.9) compared with no exercise. To achieve at least a 25% reduction in the odds of developing GDM, PE and GH, pregnant women need to accumulate at least 600 MET-min/week of moderate-intensity exercise (eg, 140 min of brisk walking, water aerobics, stationary cycling or resistance training). SUMMARY/CONCLUSIONS: In conclusion, exercise-only interventions were effective at lowering the odds of developing GDM, GH and PE.

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.