Research Updates 2006–2010

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Research in this sec­tion includes excerpts from longer works by DTP staff, includ­ing mate­r­i­al on Mater­nal Metab­o­lism, Fetal Respons­es, and Post­par­tum Phys­i­ol­o­gy.

Mater­nal Metab­o­lism

Exer­cise off­sets the ele­vat­ed glu­cose response of preg­nan­cy by uti­liz­ing blood sug­ar. The evo­lu­tion­ary biol­o­gy mod­el is use­ful for under­stand­ing that an abil­i­ty to store ener­gy in preg­nan­cy more read­i­ly than at any oth­er time is a sur­vival mech­a­nism that may have evolved in ear­ly humans. Because rig­or­ous phys­i­cal demands of sur­vival in devel­oped coun­tries have been essen­tial­ly elim­i­nat­ed from con­tem­po­rary life and processed foods have become a norm, it is easy to see how meta­bol­ic dys­func­tion in the form of hypo­glycemia, hyper­glycemia or dia­betes is increas­ing­ly gen­er­at­ed in preg­nan­cy. Thus, pre­ven­tion and/or man­age­ment of ges­ta­tion­al dia­betes that includes healthy nutri­tion and exer­cise are well accept­ed.

Ges­ta­tion­al Dia­betes, Over­weight & Strength Train­ing

Over­weight preg­nant women with dia­betes requir­ing insulin are able to reduce the amount of insulin they require when they par­tic­i­pate in reg­u­lar strength train­ing three times a week or more.

Source: Brankston GN, Mitchell BF, Ryan EA, Okun NB. Resis­tance exer­cise decreas­es the need for insulin in over­weight women with ges­ta­tion­al dia­betes mel­li­tus. Am J Obstet Gynecol. 190(1):188–93. 2004.

There is evi­dence for meta­bol­ic imprint­ing of child­hood obe­si­ty in the fetus exposed to the hor­mon­al milieu of ges­ta­tion­al dia­betes mel­li­tus (either with or with­out pre­ex­ist­ing mater­nal dia­betes).

Source: Wright CS, Rifas-Shi­man SL, Rich-Edwards JW, Taveras EM, Gill­man MW, Oken E. Intrauter­ine expo­sure to ges­ta­tion­al dia­betes, child adi­pos­i­ty, and blood pres­sure, Amer­i­can J Hyper­ten­sion 22(2):215–220. 2009.

Fur­ther, insulin-stim­u­lat­ed rates of mito­chon­dr­i­al ATP syn­the­sis are reduced in insulin resis­tant off­spring of type 2 dia­bet­ic par­ents, and these off­spring have impaired insulin-stim­u­lat­ed phos­phate trans­port in mus­cle.

Source: Petersen KF, Dufour S, Shul­man GI. Decreased insulin-stim­u­lat­ed ATP syn­the­sis and phos­phate trans­port in mus­cle of insulin-resis­tant off­spring of type 2 dia­bet­ic par­ents, PLos Med 2(9):e233. 2005.

Reg­u­lar exer­cise, on the oth­er hand, expos­es the fetus to the hor­mon­al milieu asso­ci­at­ed with a phys­i­cal­ly active lifestyle. For exam­ple, lev­els of tumor necro­sis fac­tor alpha and lep­tin, meta­bol­ic mark­ers that, among oth­er things, reflect fat mass and insulin resis­tance, are both more favor­able when women (and thus their fetus­es) par­tic­i­pate in reg­u­lar weight-bear­ing exer­cise dur­ing preg­nan­cy.

Source: Clapp JF III,  Kiess W. Effects of preg­nan­cy and exer­cise on con­cen­tra­tions of the meta­bol­ic mark­ers tumor necro­sis fac­tor alpha and lep­tin.  Am. J. Obstet. Gynecol. 182(2):300–306, 2000.

The Amer­i­can Dia­betes Asso­ci­a­tion (ADA) now rec­om­mends that “…peo­ple with impaired glu­cose tol­er­ance should begin and con­tin­ue a pro­gram of weight con­trol, includ­ing at least 150 min­utes per week of mod­er­ate to vig­or­ous phys­i­cal activ­i­ty and a health­ful diet with mod­est ener­gy restric­tion (Lev­el of evi­dence: A)”. In addi­tion, unless there are con­traindi­ca­tions, the ADA rec­om­mends peo­ple with type 2 dia­betes per­form resis­tance exer­cise 3 times per week, tar­get­ing all major mus­cle groups.

Fetal Respons­es

Fetal Car­dio­vas­cu­la­ture and Hemo­dy­nam­ics

A recent study found that the fetus­es of preg­nant women who par­tic­i­pate in aer­o­bics demon­strate a ben­e­fi­cial train­ing effect, i.e., they exhib­it low­er rest­ing puls­es and greater vari­abil­i­ty than fetus’ of moth­ers who do not par­tic­i­pate in aer­o­bics.

Source: May LE et al. Exer­cise Dur­ing Preg­nan­cy Ben­e­fits Baby. Exper­i­men­tal Biol­o­gy 2008 sci­en­tif­ic con­fer­ence; 121st annu­al meet­ing of the Amer­i­can Phys­i­o­log­i­cal Soci­ety. 2008.

The fetal heart rate nor­mal­ly accel­er­ates but main­tains vari­abil­i­ty dur­ing and after exer­cise.  Ges­ta­tion­al age, exer­cise type, inten­si­ty and dura­tion influ­ence the extent of change in fetal heart rate dur­ing and fol­low­ing exer­cise.

Sources: Car­pen­ter MW, Sady SP, Hoegs­berg B, et al. Fetal heart rate response to mater­nal exer­tion. JAMA 259:3006–3009, 1988; • Webb KA, Wolfe LA, McGrath MJ. Effects of acute and chron­ic mater­nal exer­cise on fetal heart rate.  J Appl Phys­i­ol 77:2207–2213, 1994; • Clapp JF III, Lit­tle KD, Cape­less EL. Fetal heart rate response to sus­tained recre­ation­al exer­cise.  Am J Obstet Gynecol 168:198–206, 1993.

A study—involving acute exer­cise in moth­ers with high trait anx­i­ety scores–found sig­nif­i­cant­ly high­er pul­satil­i­ty index (PI) val­ues in the umbil­i­cal artery, sig­nif­i­cant­ly low­er PI val­ues in the fetal mid­dle cere­bral artery and sig­nif­i­cant­ly low­er cere­bro-umbil­i­cal PI ratios, sug­gest­ing a shift in blood dis­tri­b­u­tion in favor of the fetal brain in these moth­ers. While preg­nant women who exer­cise ben­e­fit from stress relief, they and their fetus­es receive addi­tion­al ben­e­fits from fit­ness train­ing effects.

Source: Sjostrom K, Valentin L, The­lin T, Marsal K. Mater­nal anx­i­ety in late preg­nan­cy and fetal hemo­dy­nam­ics.  Eur J Obstet Gynecol Reprod Biol. 74(2):149–155,  1997.

Fetal Move­ment

This 2009 study look­ing at fetal breath­ing pat­terns in exer­cis­es and con­trols found that the fetal heart rate was sig­nif­i­cant­ly low­er in the exer­cise group dur­ing fetal breath­ing and non-breath­ing move­ment peri­ods. In addi­tion, fetal short-term and over­all heart rate vari­abil­i­ty were high­er in the exer­cise group dur­ing breath­ing move­ments, three inde­pen­dent mea­sures of vagal con­trol were high­er in the exer­cise-exposed fetus­es dur­ing breath­ing move­ments, and dur­ing peri­ods of fetal non-breath­ing, there were no sig­nif­i­cant dif­fer­ences in mea­sures of vagal con­trol between groups.

Source: May LE, Mil­lion S, Gustafson KM. The Effects of Mater­nal Exer­cise on Fetal Breath­ing Move­ments, Exper­i­men­tal Biol­o­gy 2009 sci­en­tif­ic con­fer­ence; 122nd Annu­al Meet­ing of the Amer­i­can Phys­i­o­log­i­cal Soci­ety. 2009.

Oth­er stud­ies on fetal body or breath­ing move­ments have found changes to be small, incon­sis­tent and tran­sient. In prac­tice, dur­ing group exer­cise class­es moth­ers seem to be most aware of fetal limb move­ment dur­ing relax­ation, at which time they fre­quent­ly report high lev­els of activ­i­ty.  There are no reports in the lit­er­a­ture of detri­men­tal fetal out­comes in this regard.

Post­par­tum Phys­i­ol­o­gy

Mater­nal Car­dio­vas­cu­la­ture

Women with hyper­ten­sive dis­or­ders in preg­nan­cy are at increased risk for car­dio­vas­cu­lar dis­or­ders over the long term. Women with a his­to­ry of preeclamp­sia exhib­it impaired endothe­lial func­tion up to a year post­par­tum, which may be one rea­son they are at increased risk for hyper­ten­sion and car­dio­vas­cu­lar dis­ease.

Source: Agati­sa PK, Ness RB, Robers JM, Costan­ti­no JP, Kuller LH, McLaugh­lin MK. Impair­ment of endothe­lial functin in women with a his­to­ry of preeclamp­sia:  an indi­ca­tor of car­dio­vas­cu­lar risk. Am J Phys­i­ol Heart Circ Phys­i­ol 286(4):389–393. 2004

In a matched con­trol study, post­par­tum women who had preeclamp­sia demon­strat­ed per­sis­tent ele­vat­ed cen­tral reti­nal artery sys­tolic veloc­i­ty, sug­gest­ing dis­tal vaso­con­stric­tio.

Source: Gian­ni­na G, Belfort MA, Cruz AL, Herd JA. Per­sis­tent cer­brovas­cu­lar changes in post­par­tum preeclamp­tic women:  a Doppler eval­u­a­tion. Am J Obstet Gynecol 177(5):1213–1218. 1997.

Metab­o­lism

Although women with hyper­ten­sive dis­or­ders often report sig­nif­i­cant declines in health sta­tus post­par­tum, women with ges­ta­tion­al dia­betes do not report declines in health sta­tus any more fre­quent­ly than moth­ers with­out either of these dis­or­ders. How­ev­er, there are meta­bol­ic issues for both moth­er and off­spring that need to be addressed in part with exer­cise, if long-term health is a goal.

Source: Kim C„ Brawarsky P,Jackson RA, Fuentes-Afflick E, Haas JS. Changes in health sta­tus expe­ri­enced by women with ges­ta­tion­al dia­betes and preg­nan­cy-induced hyper­ten­sion. J Women’s Health 14(8):729–736. 2005.

The preva­lence of ade­quate exer­cise in this group is low and high­ly depen­dent on social sup­port.

Source: Smith BJ, Che­ung NW, Bau­man AE, Zehle K, McLean M. Post­par­tum phys­i­cal activ­i­ty and relat­ed psy­choso­cial fac­tors among women with recent ges­ta­tion­al dia­betes mel­li­tus. Dia­betes Care (28(11):2650–2654. 2005.

As women with ges­ta­tion­al dia­betes are at increased risk for the devel­op­ment of type 2 dia­betes, iden­ti­fi­ca­tion and appro­pri­ate inter­ven­tion that includes exer­cise is impor­tant for this pop­u­la­tion.

Sources: Case J, Willough­by D, Haley-Zitlin V, Mabee P. Pre­vent­ing type 2 dia­betes after ges­ta­tion­al dia­betes. Dia­betes Educ 32(6):877–886. 2006.  • Kjos, SL. After preg­nan­cy com­pli­cat­ed by dia­betes: post­par­tum care and edu­ca­tion. Obstet Gynecol Clin­ics NA 34(2): 335–349. 2007.

Deter­min­ing women’s beliefs and cur­rent behav­iors can pro­vide clues to help­ing design effec­tive dai­ly exer­cise rou­tines.

Source: Downs DS, Ulbrecht JS. Under­stand­ing exer­cise beliefs and behav­iors in women with ges­ta­tion­al dia­betes, Dia­betes Care 29(2):236–240. 2006.

Two strate­gies that include exer­cise are being sug­gest­ed and inves­ti­gat­ed to pre­vent and improve adverse post­par­tum out­comes for over­weight and obese women. One is devel­op­ing weight man­age­ment inter­ven­tions for women ear­ly in the child­bear­ing years as a pre­ven­ta­tive. The oth­er is the Active Moth­ers Post­par­tum (AMP) approach, devel­op­ing indi­vid­u­al­ized behav­ior change inter­ven­tions for post­par­tum weight loss based on the teach­able moment con­cept.

Sources: Keller C, Records K, Ainsworth B, Per­mana P, Coon­rod DV. Inter­ven­tions for weight man­age­ment in post­par­tum women. JOGNN 37(1):71–79. 2008.  • Ost­bye T, Krause KM, Bow­er RJN, Love­la­dy CA et al. Active Moth­ers Post­par­tum (AMP): ratio­nale, design and base­line char­ac­ter­is­tics. J Women’s Health 17(10):1567–1575. 2008.

Hope­ful­ly, these approach­es to increas­ing phys­i­cal activ­i­ty in women at risk for meta­bol­ic dis­or­ders and obe­si­ty fol­low­ing preg­nan­cy will yield evi­dence about how exer­cise helps reduce the risk for fur­ther prob­lems for these women, and how tar­get pop­u­la­tions can be iden­ti­fied and become moti­vat­ed to par­tic­i­pate.