Pregnancy and Exercise Emily Jones, MD May 12, 2009

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ObjectivesDiscuss anatomical and physiological changes that occur during pregnancyDiscuss how these changes affect exercise in pregnancyReview Risks/benefits of

exercise in pregnancyReview Exercise prescription

and counseling for pregnancy

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Anatomical Changes: uterusExpanding uterus Elevated center of gravityProgressive lumbar lordosisTheoretical increased risk of fall40 to 50% report lower back pain

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Back pain Other recommendationsSupport beltsWater exerciseCore exercisesTylenol

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Anatomical Changes: weightIncreased total body weight 25lbs average weight gainCauses 5 x the weight on jointsSoft tissue edema occurs in >80%Can cause nerve entrapments or compression neuropathiesCarpal tunnel most common

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Anatomical changes: ligamentous laxityIncreases as pregnancy progresses? Due to increase in relaxinWidening of symphysis pubis SI joint laxityIncrease pain SI, pubicPeripheral joint laxityNo known evidence of laxity leading to increased injuries

MattR (M) - subjective complaints seem to be associated with estrogen and progesterone levels*Increase in relaxin? One study of 21 women showing poor correlationRelaxin maybe contributing factor to why more in men than women, no demonstrated increased risk in pregnancy

Specific relaxin receptors in ACL even in non-pregnant women

Pregnancy Physiology: CardiovascularBlood Volume increases up to 50% Sodium/total water retentionHeart Rate increases ~20%Stroke volume increasesCO up by 30 to 50% (1.5L)SVR decreases (progesterone) contributes to MAP one by 5 to 10mmEspecially 2nd trimester

*CO = SV x HRAll help circulation to fetus

Pregnancy Physiology: Cardiovascular

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Pregnancy physiology with exerciseHeart rate normal response vs bluntedMax HR no longer guide to monitoring intensity during pregnancyPrevious ACOG guidelines were to not exceed 140bpmCurrently recommended to use

perceived exertionBorg scaleTalk test

*140 came from 60% of VO2 of women in reproductive age

Pregnancy physiology with exerciseNo shown adverse effects on uterine blood flow due to redistribution to exercising musclesFHR usually up 10 to 30 beats in response to maternal exerciseFHR decreases seen in 9%

*Possible role of maternal hypoxia in increased FHR and catecholamineslikely vagal, cord compression

Pregnancy Physiology: Respiratory PhysiologyIncreased secretionsIncreased chest circumference (~ 2cm)Diaphragm rises up to 4cmDecreased FRC ~20%, respiratory reserve volume Increased oxygen consumption ~20%Increased Tidal Volume 30 to 50%Increased minute ventilation Primary respiratory alkalosis of pregnancyNo Change FEV1

*Secretions d/t estrogenProgesterone increases respiratory driveIncreased oxygen consumption likely d/t increased fetal demandsMost of increase in min vent d/t increased TVFRC mostly down due to decrease in reserve vol and residual vol

Respiratory Physiology

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Respiratory with exerciseSubjective and max exercise performance decreasedDuring mild exercise increased respiratory frequency, min ventilation and oxygen consumptionDuring moderate to intense exercise seems to overwhelm adaptive changes that occur at restRespiratory frequency decreases, lower TV and max O2 consumption

*a few argue not necessary to have decreased max aerobic power compared to non-pregnantArteriovenous O2 differences decreased during treadmill exercise in pregnancyIncreased resting O2 requirementIncreased work of breathing d/t uterusDecreased O2 available for exerciseExercise requires higher VO2

Respiratory with exercise

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Pregnancy physiology: ThermoregulatoryIncreased basal metabolic rateIncreased heat productionBetter heat dissipation in pregnancyIncreased surface area and SVR Increased risk of dehydration

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Pregnancy Physiology: Thermoregulation with exerciseIn non-pregnant controls body temp increases 1.5 deg C during moderate intensity exercise in the first 30 min60 minutes at 55% VO2 max in pregnant women increase of 0.6 deg CIn animal studies maternal temp increase of >1.5 deg C associated with major congenital malformationsSuggestive that maternal hyperthermia >39 deg C during first 45 to 60 days may be teratogenicNo conclusive studies in humansHyperthermia associated with exercise never directly associate with teratogenic

*Fetal temperatures ~1 deg C higher than maternal

Pregnancy outcomes improved by exerciseGestation DiabetesPreeclampsiaWeight gainImproved mental healthOverall decreased

subjective discomforts

*Studies table

Delivery outcomes improvedDecreased time of active laborDecreased interventions pitocin, forceps, c-sectionIncreased fetal tolerance of delivery

*Clapp 2000 for decreased interventions specifically weight bearing aerobic running and aerobics

Am J Obstet Gynecol 163: 1799-1805, 1990.

Exercise(n=87)Control(n=44)Incidence of PTL9%9%Length of Gestation277 d282 dIncidence of c-section6%30%Incidence of operative vaginal delivery6%20%Duration of labor264 min382 minClinical evidence of fetal distress26%50%

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Gestation DiabetesRetrospective studies show exercise can decreaseEspecially in BMI > 33Minimal data on diabeticsGreater normalization of glycemic control after 4 weeks than diet aloneDecreased insulin need

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Gestational Diabetes

Author, yearStudy typeActivity periodsizeRR, OR, CIDempsey et al (2004) Case-controlYear before1st 20 weeksBoth periods155 cases366 controlsAny vs. none 0.45 (0.28-0.74)Vigorous vs. none 0.29 (0.16-.51) vs. none 0.52 (0.33-0.80)Vigorous vs. none 0.34 (0.19-0.63)Active both vs. inactive both 0.40 (0.23-0.68)Dempsey et al (2004) ProspectiveYear before~12 weeksBoth909Any vs. none 0.44 (0.21-0.91)Any vs. none 0.69 (0.37-1.29)Any vs. inactive both 0.31 (0.12-0.79)Zhang et alprospectivePotentially 10yrs before pregnancy21,765Mean weekly total activity score highest vs. lowest quintile 0.81 (0.68-1.01)Mean weekly vigorous activity score highest vs. lowest quintile 0.77 (0.69-0.94)Brisk/very brisk walking vs. casual walking with no vigorous activity 0.66 (0.46-0.95) 15 flights stairs/day vs 2 flights stairs/day with no vigorous activity 0.50 (0.27-0.90)Oken et al 2004prospectiveYear before~20 weeks gestBoth1805Vigorous vs. none 0.56 (0.33-0.95)Vigorous vs. none 0.90 (0.47-1.70)Any vs none 0.49 (0.24-1.01)Dye et al 1997Case-controlEntire pregnancy372 cases12, 404 controlsNone vs. any 1.0 (0.8-1.3)BMI >33.0 none vs. any 1.9 (1.2-3.1)

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Preeclampsia43% decrease with moderate exercise vs. sedentaryShown in one studyRisk decreases more with increasing time spent exercising

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Preeclampsia

Sorenson et al 2003Case-controlYear before

1st 20 wks preg

Both201 cases383 controlsAny vs. none 0.67 (0.42-1.08)Vigorous vs. none 0.40 (0.23-0.69)Any vs. none 0.65 (0.43-0.99)Vigorous vs. none 0.46 (0.27-0.79)Active both vs. inactive both 0.59 (0.35-0.98) Saftlas et al 2004Nested Case-controlYear before

Debunking the risks of aerobic exerciseNo increased risk of:MisscarriageCongenital malformationsEctopicPre-term laborPlacental insufficiencyIUGRUnexplained fetal deaths

*Reproduced in many studies

Exercise and Birth WeightOne study showed continuation of exercise at or above 50% preconception levels = significant reductions (-310g)Another trial showed no difference b/w birth weight with non-exercises and vigorous exercisesOne study found longer duration exercise (40 to 60min 4-5 x week) of moderate, weight-bearing reduced growth, but reducing duration to 20 min increased growthMeta-analysis of 30 studies no difference except in vigorous exercises in 3rd trimester decreased fetal weight 200 to 400g

*Put citations from utd article referencesPossible reasons for increased growth with moderate/short exercise actually increased placental blood flowReduced weight babies with longer exercise less body fat but no decrease in healthMeta-anal results postulate possible cause as decrease in calories

Pre-term birthNo increased risk in exercising women with uncomplicated pregnancy and no other risk factors for pre-term laborPhysical activity associated with a slight increase in uterine contractionsDehydration can worsen

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ContraindicationsAbsoluteSignificant cardiac diseaseRestrictive lung diseaseCervical incompetenceMultiple gestationPlacental abruptionPlacenta previaPremature laborRupture of membranespreeclampsia

RelativeSevere anemiaUnevaluated arrhythmiaBronchitisPoorly controlled DM, htn, sz d/o, thyroid dzExtreme obesity or low BMISedentary lifestyleFetal growth restrictionHeavy smoking

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ACOG 2002 GuidelinesIn the absence of contraindications, pregnant

women should be encouraged to engage in regular, moderate intensity physical activity to continue to derive health benefits during their pregnancies as they did prior to pregnancy30 minutes or more of moderate exercise per day recommendedAvoid the supine position during exercise as much as possibleRecommend against scuba diving during pregnancy, sports at risk for abdominal trauma

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ACOG 2002 Guidelines cont.Exercise may benefit women with gestational diabetesCompetitive athletes may require close obstetric supervisionModerate exercise during postpartum does not negatively impact nursing and neonatal weight gainReturn to physical activity after pregnancy

reduces the risk of postpartum depression

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Exercise prescriptionVery similar to non-pregnant individualsSedentary women can safely begin exercising during pregnancyNeed to be flexible adapt as pregnancy progressesActive women may be advised to

restrain from very strenuous activities and competitionPre-exercise medical screening

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Exercise prescriptionTypeIntensity DurationFrequencyProgression

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Plug for water exerciseCentripetal shift in blood volumeLower forces across weight bearing jointsBody heat readily dissipatedBalance and falling

not an issue

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What about weight lifting risks?Lower weights, multiple repetitionsAvoid heavy or isometricNo increased risk of injuryNo obvious positive/negative effects on weight gain pregnancy, complications, birth weight, pre-term laborPossibly helpful :Core strength = less lower back painBetter tolerate weight gain

*No studies to support avoiding heavy or isometric theoretical danger d/t increased in bpMech likely risk of strain lower back and possibly valsalva

Exercise positionAvoid supine position after 1st trimesterRelative obstruction of venous returnCO down ~ 9%Standing positionCO down ~ 18%lower birth weights in women who worked standing during 3rd trimester

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Exercises to AvoidContact sportsHockey, basketball, soccerRisk of traumaSkiing, biking, gymanstics, horseback ridingScuba divingDecompression problems fetusAltitudeDecreased oxygen

*Scuba diving risk b/c

Intensity Moderate intensity 3 to 4 METs as with non-pregnantTo develop or maintain physical fitness up to 6 to 7 METs also appears safe if pregnancyTailor on pre-pregnancy fitnessUse RPE, talk testNo longer use HR cut off

*Pre-pregnancy exercisers able to engage in high intensity (not quantified?) jogging/aerobics avg 43 min, 144bpm with no adverse outcomes

DurationAt least 150 min/week of moderate intensityCareful attention to hydration, heat and caloric intake in exercise > 45 min in pregnancy

*Risk of hypoglycemia greater

Nutritional RecommendationsApproximately 300kcal/day moreSlightly more 2nd tri, slightly less 3rdMore if exercisingIncreased risk of hypoglycemiaIncreased carbohydrate need

MattR (M) - increased carb metabolism and lower glycogen reserves*Utilize carbohydrates at a higher rate than non-pregnant women d/t fetal demandsSome increased risk of hypoglycemia

Glucose utilization

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Frequency and ProgressionSimilar recommendations to non-pregnantExpect activity and fitness level to decrease as pregnancy progresses

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Warning signs to Terminate ExerciseVaginal bleedingDyspnea prior to exertionDizzinessHeadacheChest pain

Muscle weaknessSigns of thrombophlebitisUterine contractionsDecreased fetal movementLeakage of fluid

*ACOG 2002

NCAA guidelines

Guideline published 2002Acknowledges lack of research addressing intense physical exercise & pregnancyCite expert opinion recommending to avoid participation in contact sports after 14 wks EGATeam physician job is to advise student-athlete:

- Risk, benefits, effects on competitive ability- One-year extension of 5 yr eligibility period for reasons of pregnancySigned informed consent recommended if athlete chooses to compete

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PostpartumProbably safe to resume training within 2 weeks of delivery in competitiveNo proof of increased injury to pelvic floor/abdominal musclesFaster regain of abdominal musclesImproved bladder controlCare with return to high impact

activities such as runningDecreased post partum depressionIncreased weight loss

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Postpartum breastfeedingOverall no decrease in ability to breastfeed when exercisingStrenuous training can decrease milk production in breast feeding womenFeed prior to exerciseDecreased discomfort from engorgedLess chance of acidity in breast milk

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SummaryMany anatomical and physiological changes during pregnancyPregnant women should be encouraged to exercise regularlyFlexible and individual exercise prescriptionAvoid contraindicated exercises and conditionsHeat, altitude, depthContinue exercising postpartum

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*Increase in relaxin? One study of 21 women showing poor correlationRelaxin maybe contributing factor to why more in men than women, no demonstrated increased risk in pregnancy

Specific relaxin receptors in ACL even in non-pregnant women*CO = SV x HRAll help circulation to fetus*

*140 came from 60% of VO2 of women in reproductive age *Possible role of maternal hypoxia in increased FHR and catecholamineslikely vagal, cord compression*Secretions d/t estrogenProgesterone increases respiratory driveIncreased oxygen consumption likely d/t increased fetal demandsMost of increase in min vent d/t increased TVFRC mostly down due to decrease in reserve vol and residual vol*

*a few argue not necessary to have decreased max aerobic power compared to non-pregnantArteriovenous O2 differences decreased during treadmill exercise in pregnancyIncreased resting O2 requirementIncreased work of breathing d/t uterusDecreased O2 available for exerciseExercise requires higher VO2

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*Fetal temperatures ~1 deg C higher than maternal*Studies table*Clapp 2000 for decreased interventions specifically weight bearing aerobic running and aerobics*

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*Reproduced in many studies*Put citations from utd article referencesPossible reasons for increased growth with moderate/short exercise actually increased placental blood flowReduced weight babies with longer exercise less body fat but no decrease in healthMeta-anal results postulate possible cause as decrease in calories*

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*No studies to support avoiding heavy or isometric theoretical danger d/t increased in bpMech likely risk of strain lower back and possibly valsalva*

*Scuba diving risk b/c *Pre-pregnancy exercisers able to engage in high intensity (not quantified?) jogging/aerobics avg 43 min, 144bpm with no adverse outcomes*Risk of hypoglycemia greater*Utilize carbohydrates at a higher rate than non-pregnant women d/t fetal demandsSome increased risk of hypoglycemia*

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*ACOG 2002*

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