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

Heat stress and adverse pregnancy outcome: Prospective cohort study

OBJECTIVE

To explore the relationship between occupational heat exposure, physiological heat strain indicators and adverse outcomes in pregnant women.

DESIGN

Prospective cohort.

SETTING

Workplaces in Tamil Nadu, India.

SAMPLE

A cohort of 800 pregnant women engaged in moderate to heavy physical work in 2017-2019 and 2021-2022.

METHODS

Participants were recruited at between 8 and 14 weeks of gestation. Occupational heat exposure and heat strain indicators were captured each trimester. 'Heat exposed' was defined as heat stress exceeding the threshold limit value (TLV) for safe manual work (with maximum wet-bulb globe temperatures of 27.5°C for a heavy workload and 28.0°C for a moderate workload). Physiological heat strain indicators (HSIs) such as core body temperature (CBT) and urine specific gravity (USG) were measured before and after each shift. Heat-related health symptoms were captured using the modified HOTHAPS questionnaire.

MAIN OUTCOME MEASURES

The main outcome measures included (1) a composite measure of any adverse pregnancy outcome (APO) during pregnancy (including miscarriage, preterm birth, low birthweight, stillbirth, intrauterine growth restriction and birth defects), (2) a composite measure of adverse outcomes at birth (3) and miscarriage.

RESULTS

Of the 800 participants, 47.3% had high occupational heat exposure. A rise in CBT was recorded in 17.4% of exposed workers, and 29.6% of workers experienced moderate dehydration (USG ≥ 1.020). Heat-exposed women had a doubled risk of miscarriage (adjusted odds ratio, aOR 2.4; 95% confidence interval, 95% CI 1.0-5.7). High occupational heat exposure was associated with an increased risk of any adverse pregnancy and foetal outcome (aOR 2.3; 95% CI 1.4-3.8) and adverse outcome at birth (aOR 2.0; 95% CI 1.2-3.3).

CONCLUSIONS

High occupational heat exposure is associated with HSIs and adverse pregnancy outcomes in India.

Environmental heat stress on maternal physiology and fetal blood flow in pregnant subsistence farmers in The Gambia, west Africa: an observational cohort study

BACKGROUND

Anthropogenic climate change has caused extreme temperatures worldwide, with data showing that sub-Saharan Africa is especially vulnerable to these changes. In sub-Saharan Africa, women comprise 50% of the agricultural workforce, often working throughout pregnancy despite heat exposure increasing the risk of adverse birth outcomes. In this study, we aimed to improve understanding of the pathophysiological mechanisms responsible for the adverse health outcomes resulting from environmental heat stress in pregnant subsistence farmers. We also aimed to provide data to establish whether environmental heat stress also has physiological effects on the fetus.

METHODS

We conducted an observational cohort study in West Kiang, The Gambia, at the field station for the Medical Research Council Unit The Gambia at London School of Hygiene & Tropical Medicine (named the MRC Keneba field station). Pregnant women who were aged 16 years or older and who were at <36 weeks' gestation of any gravida or parity were invited to participate in the study. Participants were eligible if they were involved in agricultural or related manual daily tasks of living. Participants were ineligible if they refused to provide consent, had multiple pregnancies (eg, if they had twins), were acutely unwell, or were diagnosed with pre-eclampsia or eclampsia. Heat stress was measured by wet bulb globe temperature (WBGT) and by using the universal thermal climate index (UTCI), and maternal heat strain was directly measured by modified physiological strain index calculated from heart rate and skin temperature. Outcome measures of fetal heart rate (FHR) and fetal strain (defined as a FHR >160 beats per min [bpm] or <115 bpm, or increase in umbilical artery resistance index) were measured at rest and during the working period. Multivariable repeated measure models (linear regression for FHR, and logistic regression for fetal strain) were used to evaluate the association of heat stress and heat strain with acute fetal strain.

FINDINGS

Between Aug 26, 2019, and March 27, 2020, 92 eligible participants were recruited to the study. Extreme heat exposure was frequent, with average exposures of WBGT of 27·2°C (SD 3·6°C) and UTCI equivalent temperature of 34·0°C (SD 3·7°C). The total effect of UTCI on fetal strain resulted in an odds ratio (OR) of 1·17 (95% CI 1·09-1·29; p<0·0001), with an adjusted direct effect of OR of 1·12 (1·03-1·21; p=0·010) with each 1°C increase in UTCI. The adjusted OR of maternal heat strain on fetal strain was 1·20 (1·01-1·43; p=0·038), using the UTCI model, with each unit increase.

INTERPRETATION

Data from our study show that decreasing maternal exposure to heat stress and heat strain is likely to reduce fetal strain, with the potential to reduce adverse birth outcomes. Further work that explores the association between heat stress and pregnancy outcomes in a variety of settings and populations is urgently needed to develop effective interventions.

FUNDING

The Wellcome Trust.

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.

Why can't I exercise during pregnancy? Time to revisit medical 'absolute' and 'relative' contraindications: systematic review of evidence of harm and a call to action

BACKGROUND

Clinical guidelines recommend pregnant women without contraindication engage in regular physical activity. This is based on extensive evidence demonstrating the safety and benefits of prenatal exercise. However, certain medical conditions or contraindications warrant a reduction, modification or cessation of activity due to potential health risks.

AIM

To review and evaluate the evidence related to medical disorders which may warrant contraindication to prenatal exercise.

METHODS

Online databases were searched up to 5 April 2019. Forty-four unique studies that reported data on our Population (pregnant women with contraindication to exercise), Intervention (subjective/objective measures of acute or chronic exercise), Comparator (not essential) and Outcomes (adverse maternal or fetal outcomes) were included in the review.

KEY FINDINGS

We found that the majority of medical conditions listed as contraindications were based on expert opinion; there is minimal empirical evidence to demonstrate harm of exercise and benefit of activity restriction. We identified 11 complications (eg, gestational hypertension, twin pregnancy) previously classified as contraindications where women may in fact benefit from regular prenatal physical activity with or without modifications. However, the evidence suggests that severe cardiorespiratory disease, placental abruption, vasa previa, uncontrolled type 1 diabetes, intrauterine growth restriction, active preterm labour, severe pre-eclampsia and cervical insufficiency are associated with strong potential for maternal/fetal harm and warrant classification as absolute contraindications.

CONCLUSION

Based on empirical evidence, we provide a call to re-evaluate clinical guidelines related to medical disorders that have previously been considered contraindications to prenatal exercise. Removing barriers to physical activity during pregnancy for women with certain medical conditions may in fact be beneficial for maternal-fetal health outcomes.

Uterine Artery Doppler Velocimetry During Individually Prescribed Exercise in Pregnancy

OBJECTIVE

To evaluate uterine artery blood flow in response to typical exercise sessions performed in pregnancy in accordance with the current recommendations from the American College of Obstetricians and Gynecologists and the U.S. Department of Health and Human Services.

METHODS

This prospective cross-sectional study measured uterine artery Doppler velocimetry in healthy pregnant women after individually prescribed exercise, including 1) moderate-intensity exercise (40-59% of heart rate reserve) in both nonexercisers and regular exercisers and 2) vigorous-intensity exercise (60-84% of heart rate reserve) in women who regularly engage in exercise. Resting uterine artery Doppler measures were obtained after a 20-minute fetal heart tracing; then the exercise session was performed. Immediately after the exercise session ended, the participants returned to the semirecumbent, leftward tilt position for ultrasound examination. Uterine artery measures were obtained 3.4±0.9 minutes (mean±SD) postexercise.

RESULTS

Forty-five healthy pregnant women participated in the study: 30 regular exercisers and 15 nonexercisers. For the moderate-intensity session, mean gestational age was 31.1 and 31.7 weeks for the exercisers and nonexercisers, respectively. Mean uterine artery Doppler indices (pulsatility index, resistance index, systolic/diastolic ratio) did not significantly change with exercise. For the vigorous-intensity session, the average gestational age was 31.5 weeks. After vigorous activity, all mean uterine artery Doppler indices showed reductions postexercise, for example, pulsatility index decreased from 0.63±0.12 to 0.58±0.12 (P=.04).

CONCLUSION

Individually prescribed exercise according to guidelines for pregnant women does not adversely alter uterine artery Doppler values, suggesting that uterine blood flow is not reduced as a result of exercise.

Exercise as a therapeutic intervention to optimize fetal weight

The Developmental Origins of Health and Disease suggest the in utero environment programs offspring obesity and cardiovascular disease. Therefore, there is a need to implement safe therapeutic interventions that do not involve the intake of medications or biological products during pregnancy that can improve maternal and fetal health. Prenatal exercise is established to promote maternal and fetal health. It is generally recommended that women accumulate at least 150 min per week of moderate-intensity exercise. It has been demonstrated that prenatal exercise maintains healthy weight gain and improves maternal glucose control, maternal cardiac autonomic control, placental efficiency (increases angiogenesis, downregulates genes involved in fatty acid transport and insulin transport across the placenta, and upregulates genes involved in amino acid transport across the placenta), and oxidative stress. These adaptations following exercise improve maternal metabolism and provide adequate uteroplacental perfusion. In this review, we will focus on exercise as a therapeutic intervention to optimize fetal weight. It has been established that prenatal exercise does not increase the risk of having a small for gestational age baby. To the contrary, prenatal exercise has been associated with the prevention of excessive fat accumulation in the newborn and the maintenance of fetal muscle mass.

Exercise in Pregnancy: A Clinical Review

Context:

Health professionals who care for pregnant women should discuss potential health benefits and harms of exercise. Although most pregnant women do not meet minimal exercise recommendations, there are a growing number of physically active women who wish to continue training throughout pregnancy.

Evidence Acquisition:

A search of the Web of Science database of articles and reviews available in English through 2014. The search terms exercise pregnancy, strenuous exercise pregnancy, and vigorous exercise pregnancy were used.

Study Design:

Clinical review.

Level of Evidence:

Level 3.

Results:

With proper attention to risk stratification and surveillance, exercise is safe for the mother and fetus. Benefits of exercise in pregnancy include reduction in Cesarean section rates, appropriate maternal and fetal weight gain, and managing gestational diabetes. Exercise as a means of preventing gestational diabetes, preeclampsia, or perinatal depression cannot be reliably supported. Overall, the current evidence suffers from a lack of rigorous study design and compliance with physical activity interventions.

Conclusion:

Research thus far has been unable to consistently demonstrate proposed benefits of exercise in pregnancy, such as preventing gestational diabetes, preeclampsia, or perinatal depression. However, moderate- and high-intensity exercise in normal pregnancies is safe for the developing fetus and clearly has several important benefits. Thus, exercise should be encouraged according to the woman’s preconception physical activity level.

Physical activity and maternal-fetal circulation measured by Doppler ultrasound

OBJECTIVE

To examine the association of physical activity on maternal-fetal circulation measured by uterine and umbilical artery Doppler flow velocimetry waveforms.

STUDY DESIGN

Participants included 781 pregnant women with Doppler ultrasounds of the uterine and umbilical artery and who self-reported past week physical activity. Linear and generalized estimating equation regression models were used to examine these associations.

RESULT

Moderate-to-vigorous total and recreational activity were associated with higher uterine artery pulsatility index (PI) and an increased risk of uterine artery notching as compared with reporting no total or recreational physical activity, respectively. Moderate-to-vigorous work activity was associated with lower uterine artery PI and a reduced risk of uterine artery notching as compared with no work activity. No associations were identified with the umbilical circulation measured by the resistance index.

CONCLUSION

In this epidemiologic study, recreational and work activity were associated with opposite effects on uterine artery PI and uterine artery notching, although associations were modest in magnitude.

The effect of vigorous exercise during pregnancy

Pregnant women without medical or obstetric problems should be encouraged to exercise. The paucity of experimental data on exercise in pregnancy forces recommendations to be drawn from a synthesis of available information. Vigorous exercise during pregnancy seems to pose no adverse maternal or neonatal outcomes. Nonetheless, the safety of vigorous exercise necessitates surveillance of fetal growth, the woman's weight, nutritional intake, and exercise duration and intensity.

Effect of maternal fasting on uterine arterial blood flow

AIM

To determine the effect maternal diet pattern on the uterine artery Doppler flow velocimetry.

METHODS

This is a cross-sectional observational study. The uterine artery Doppler flow velocimetry was measured between 20 and 24 weeks' gestation in healthy pregnant women observing Ramadan. For each fasting mother, a non-fasting healthy pregnant woman was recruited as a control. Maternal blood glucose level was measured.

RESULTS

A total of 106 pregnant women were studied. The mean hours since last oral intake were significantly longer, and the maternal glucose level was significantly lower in the study group than in the control group. The Mean (95% CI) of the uterine artery pulsatility index, resistance index, peak systolic velocity, end diastolic velocity and systolic/diastolic ratio was similar in both groups.

CONCLUSION

Maternal fasting is not associated with significant changes in the uterine artery Doppler flow velocimetry.

Practical exercise advice during pregnancy: guidelines for active and inactive women

Many women enjoy regular exercise as a part of a healthy lifestyle and may wish to continue exercising after they become pregnant. Some previously sedentary women may want to start an exercise program during pregnancy. Primary care and sports medicine physicians should understand the contraindications (eg, hypertension, diabetes, placenta previa, preeclampsia) and the concerns about exercise during pregnancy (eg, fetal nutrition, risk of preterm labor) and be able to offer reasonable guidelines to women who wish to start or continue exercise during pregnancy. Most non-weight-bearing exercises (eg, swimming, stationary bicycling) and walking are safe for pregnant women, beginning with 15 minutes of exercise three times a week and progressing as tolerated.