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SHORTREPORTOpenAccessMagnesiumconcentrationinamnioticfluidintheearlyweeksofthesecondtrimesterofpregnancyJuliaPilarBocosTerraz1,SilviaIzquierdolvarez1*,JoseLuisBancaleroFlores1,ngelGonzálezLópez2andJesúsFernandoEscaneroMarcén3AbstractBackground:Weanalysemagnesiumlevelsinamnioticfluidtoestablishnormalvaluesforthe14thto18thweekofpregnancyandestablishcriticalvaluesthatcouldbeusefuldiagnosticandtherapeuticguidelinesforpossiblecomplications.
Findings:Ninety-twosamplesofamnioticfluidobtainedbyamniocentesisaswellasthecorrespondingserumsamplesofpregnantwomenwereanalysed.
Thegestationalage(mean±SD)atwhichtheamnioticfluidsamplewasobtainedwas16.
13±1.
87weeks.
Magnesiumlevelsweredeterminedbycolorimetricassaywithchlorophosphonazo-IIIusingthetheCobasc501analyser(RocheDiagnostics).
StatisticaltreatmentofdatawasperformedusingtheSPSSprogram,version15.
0.
Resultsrevealedameanmagnesiumvalueof1.
65±0.
16mg/dLinamnioticfluidand1.
97±0.
23mg/dLinserum.
Conclusions:Itwouldbeinterestingtoextendthestudytoalargernumberofpregnantwomentodeterminevariationsinnormalmagnesiumvaluesinthethreetrimestersofpregnancy.
BackgroundAmnioticfluidincreasesinvolumeasthefoetusgrowsandpeaksatanaverageof800mLatapproximately34weeksofgestation.
Approximately600mLofamnioticfluidsurroundsthebabyatfullterm(40weeks).
Thisfluidiscirculatedconstantlybythebabyinhalingandswallowingexistingfluidandreplacingitthroughexha-lationandurination[1].
Amnioticfluidaccomplishesnumerousfunctions:(1)itprotectsthefoetusfrominjurybycushioningsuddenblowsormovements,(2)itenablesfoetalmovementandsymmetricalmusculoskele-taldevelopment,(3)itmaintainsarelativelyconstanttemperatureandthusprotectsthefoetusfromheatloss,and(4)itensuresproperfoetallungdevelopment[1,2].
Lowlevelsofmagnesiuminamnioticfluidareasso-ciatedwithpregnancycomplicationssuchaspreeclamp-sia[3]anddiabetes[4,5].
Magnesiumsupplementshavebeendemonstratedtoreducethefrequencyofdelayedfoetalgrowth,especiallyinlow-birth-weightbabies.
How-ever,thegeneralbenefitsofmagnesiumforfoetalgrowthanddevelopmenthavenotbeendemonstrated[6];theMagpiestudy[7],forexample,concludedthattreatmentwithmagnesiumdidnotimprovepreeclampsia.
Consequently,knowledgeofthevaluesforthisioninnormalamnioticfluidmayprovideapreventiveandearlydiagnosisofcertainmaternalandfoetalpatholo-gies.
Amniocentesisisperformed,ifindicated,fromthesecondtrimesterofpregnancy.
Althoughmagnesiumvaluesinamnioticfluid[8-11]arereportedinthelitera-ture,noreferencevaluesareprovidedforthethreedif-ferentpregnancytrimesters.
Magnesiuminserumisreducedduringpregnancyandsoadditionalmagnesiumisrequiredinthediet[6,12,13].
Therecommendeddailyintakeforpregnantwomenishigherthanforthesameagegroupofnon-pregnantwoman,yetmostpregnantwomendonotcon-sumetherequiredamount[6].
Becausevariationsinmagnesiumvaluescouldbeuse-fulasdiagnosticandtherapeuticguidelinesforpossiblecomplications,ouraimwastodeterminemagnesiumlevelsinamnioticfluidsoastoestablishnormalvaluesforthe14-to-18-weekintervalofthesecondtrimesterofpregnancy.
*Correspondence:sizquierdo@salud.
aragon.
es1ServiciodeBioquímicaClínica,HospitalUniversitarioMiguelServet,PadreArrupe-EdificiodeConsultasExternas(3planta),50009Zaragoza,SpainFulllistofauthorinformationisavailableattheendofthearticleBocosTerrazetal.
BMCResearchNotes2011,4:185http://www.
biomedcentral.
com/1756-0500/4/1852011lvarezetal;licenseeBioMedCentralLtd.
ThisisanopenaccessarticledistributedunderthetermsoftheCreativeCommonsAttributionLicense(http://creativecommons.
org/licenses/by/2.
0),whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalworkisproperlycited.
MethodsThestudydesignandprotocolwerereviewedandapprovedbythe"EthicsCommitteeofHospitalUniver-sitarioMiguelServet"inaccordancewiththeDeclara-tionofHelsinkiandtheNurembergCode.
Allthepatientsinthestudygrantedtheirinformedconsent.
Includedinthestudywere92pregnantwomenagedbetween21and44yearsold.
Samplesizewasestab-lishedonthebasisofthemeannumberofpregnantwomenundergoingamniocentesisbetweenthe14thand18thweekofpregnancy.
Theaveragegestationalageatwhichamnioticfluidsampleswereobtainedbyamnio-centesiswas16.
13(±1.
87)weeks.
Theextractedamnio-ticfluidsamplesweresentimmediatelytothelaboratoryforcentrifugationandprocessingtodeter-minemagnesiumlevels,or,ifimmediateprocessingwasnotpossible,theywerestoredat-80°C.
ThereasonsforperformingamniocentesisonthepatientsinoursamplearesummarizedinFigure1.
Magnesiumlevelswereanalysedforboththeamnioticfluidandserumofthestudypopulation,bycolorimetricassaywithchlorophosphonazo-IIIusingtheCobasc501analyser(RocheDiagnostics).
Themeasurementintervalwas0.
24-6.
08mg/dLandthelowerdetectionthresholdwas0.
24mg/dL.
Thereferenceserumvalueforthenor-maladultpopulation(21-59years)was1.
6-2.
6mg/dL.
StatisticalanalysiswasperformedusingtheSPSSpro-gram,version15.
0.
ResultsanddiscussionResultsrevealedameanamnioticfluidvalueof1.
65±0.
16mg/dL–withthevalue1.
6mg/dLrepeatedinmanysamples–andameanserumvalueof1.
97±0.
23mg/dL.
Amnioticfluidvaluesformagnesiumwereslightlylowerthanserumvalues.
Novariationsinmagnesiumlevelsweredetectedinpatientsreferredforamniocentesistodiagnosedisordersthatcouldimplyariskforthefoetus.
Similarly,despitevariationsinamnioticfluidvolumeduringpregnancy[1],magnesiumconcentrationsremainedfairlystable.
Theseresultsareconsistentwithpreviousstudies[8-11]analysingmagnesiumlevelsinamnioticfluid;5HDVRQVIRUDPQLRFHQWHVLV2.
444.
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889.
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540DWHUQDODJH5LVNRIWULVRP\ZLWKQRUPDONDU\RW\SHWHVWHG0DWHUQDODQ[LHW\0DOIRUPDWLRQVZLWKSUHYLRXVWULVRP\(FRJUDILFPDUNHU,QIHFWLRXVGLVHDVHV+\JURPDFigure1Reasonsforperformingamniocentesisinpregnantwomen.
BocosTerrazetal.
BMCResearchNotes2011,4:185http://www.
biomedcentral.
com/1756-0500/4/185Page2of3however,thesestudiesdidnotdistinguishbetweenthethreetrimestersofpregnancy.
Fallsinamnioticfluidmagnesiumlevelsareassociatedwithpregnancycomplicationssuchaspreeclampsia[3]anddiabetes[4,5].
Magnesiumsulphate,whichhasaspecificmaternalcentralnervoussystemanticonvulsantaction,hasgainedwideinternationalacceptanceasaneffectivedrugforthetreatmentofeclampsia[14];how-ever,magnesiumtreatmentdoesnotappeartobeeffec-tiveinpreventingpreeclampsia.
Maternalhypoxiaandconvulsions,eclampsiaandepilepticseizurescanhaveaneurotoxiceffectonthefoetus.
Magnesiumsulphatemayalsoprotectlow-birth-weightinfants(under1500g)againstcerebralpalsy[15].
Magnesiumisalsoconsid-eredanimportantfactorinthepathogenesisoftoxicshocksyndrome;accordingtoonestudy[15],toxin1productionbyStaphylococcusaureuswasmaximalwhenmagnesiumconcentrationswerelow,whilehighercon-centrationssuppressedtoxin1production.
Ontheotherhand,magnesiumsulphate,whengiveninhighdosagestoobstetricpatients,cancausesignificantmaternalmorbidityandrareinstancesofmaternalmortality[14].
ConclusionsDespitetheriskassociatedwithamniocentesis,itwouldbeinterestingtoextendthestudytoalargernumberofpregnantwomenanddeterminemagnesiumvaluesforthefirst,secondandthirdtrimestersinbothnormalandabnormalpregnancies,soastoestablishnormalvaluesandcriticalrangesandbetterevaluatecomplica-tionsandtheirmanagement.
AcknowledgementsGratefulthankstotheparticipantsinthestudy.
AilishMJMaherrevisedtheEnglishinaversionofthemanuscript.
Authordetails1ServiciodeBioquímicaClínica,HospitalUniversitarioMiguelServet,PadreArrupe-EdificiodeConsultasExternas(3planta),50009Zaragoza,Spain.
2HospitalMilitardeZaragoza-MinisteriodeDefensa,Spain.
3DepartamentodeFarmacologíayFisiología,FacultaddeMedicina,UniversidaddeZaragoza,50009Zaragoza,Spain.
Authors'contributionsJPBTconceivedthestudy,participatedinitsdesignandcoordinationandhelpeddraftthemanuscript.
SIAcarriedoutlaboratorytests,participatedindesigningthestudyandperformedthestatisticalanalysis.
JLBFparticipatedinthesequencealignmentandhelpeddraftthemanuscript.
AGLcarriedouttheassaysandparticipatedindesigningthestudy.
JFEMhelpeddraftthemanuscript,reviseditcriticallyforintellectualcontentandgavefinalapprovaloftheversiontobepublished.
CompetinginterestsTheauthorsdeclarethattheyhavenocompetinginterests.
Allauthorsreadandapprovedthefinalmanuscript.
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