by a fetal movement acceleration measurement recorder Correlation between umbilical cord length and gross fetal movement ascounted Biology: X European Journal of Obstetrics & Gynecology andReproductive

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Correlation between umbilical cord length and gross fetal movement as counted by a fetal movement acceleration measurement recorder

Eiji Ryo*, Hideo Kamata, Michiharu Seto, Masayoshi Morita, Keita Yatsuki

DepartmentofObstetricsandGynecology,TeikyoUniversity,SchoolofMedicine,2-11-1,Kaga,Itabashi-ku,Tokyo,173-8606,Japan

ARTICLE INFO

Articlehistory:

Received20August2018

Receivedinrevisedform19November2018 Accepted27December2018

Availableonline10January2019

Keywords:

Fetalmovement

Fetalmovementaccelerationmeasurement recorder

Umbilicalcord Umbilicalcordlength

ABSTRACT

Introduction:Thefetalmovementaccelerationmeasurement(FMAM)recorderhasmadeitpossibleto countgrossfetalmovementsovermanyhours.Ourpurposewastoexaminetherelationshipbetween umbilicalcordlengthandfetalmovementsascountedbytheFMAMrecorder.

Methods:Sixty-twopregnantwomenrecordedfetalmovementsweeklyfrom28weekstoterm.Theratio of10-speriodsinwhichmovementoccurredtototaltimewascalculatedasamovementindex.Umbilical cordlengthwasmeasuredatdelivery.(1)Multiplelinearregressionanalyseswereconductedwithsix explanatoryvariables(primipara/multipara,anterior/posteriorlocatedplacenta,placentalweight,the meanmovementindexof28–31,32–35,and36–39week)andaresponsevaluable(umbilicalcord length).(2)Allwomenweredividedintogroupsofshorter,middle,andlongercordlength,speciﬁcally lessthan50cm,between50and60cm,andmorethan60cm.Themovementindexwascompared amongthethreegroupsat28–31,32–35,and36–39weeks.

Results:A totalof 2355.6hfrom368nightrecordswereavailable.(1)Therewerenorelationships betweenthecordlengthandthemovementindexof28–31,32–35,and36–39weeks(p=0.090,0.235, 0.129,respectively).(2)Therewerenodifferencesinthemovementindexamongthethreegroupsat28–

31and32–35gestationalweeks(p=0.096,and0.465,respectively);however,thelongercordgrouphada greatermovementindexthantheothertwogroupsat36–39weeks(p=0.0008).

Discussion:Thisstudysuggestedthatfetalmovementneartermisanimportantfactorindetermining whethercordlengthbecomesrelativelylongerinnormalpregnancies.

Introduction

The umbilical cordis an important lifeline for a fetus, and abnormalities of the umbilical cord sometimes cause fetal mortalityormorbidity[1].Oneoftheabnormalitiesisitslength.

A short cord increases the probability of non-reassuring fetal status,emergentcesareandelivery,andneonatalasphyxia[1].A longcordisassociatedwithentanglement,knots,prolapse,anda thrombusofthecord.Alongcordalsoincreasestheprobabilityof neonatalasphyxia[2,3].

Thoughlittleisknownaboutthefactorsdeterminingumbilical cordlength,fetalmovementisconsideredbymanytobeoneofthe promotingfactors.There havebeenseveralanimal experiments suggestingjust that.Moessinger etal. [4] reportedthat tensile

forces on the cord, secondary to fetal movements, were an importantdeterminantofcordlengthinrats.BaronSetal.exposed cocaine[5]andalcohol[6]tofetalratstoreducefetalmovement and demonstrated that these exposures made umbilical cords shorter.Similarly,KatzVetal.[7]exposedbeta-blockerstofetal rabbitstoreducefetalmovementandconcludedthatadecreasein fetalmovementledtoashortercord.

Ontheotherhand,severalclinicalstudiesreportedanindirect relationshipbetweencordlengthandfetalmovementsinhuman beings.Miller etal.[8]reportedthatashortumbilicalcordwasfound innewbornswithgrossstructuralorfunctionallimbdefectsthat would limit intrauterine movement. Kivistö J et al. [9] studied pregnantwomentakingselectiveserotoninreuptakeinhibitorsand foundthatnew-bornsexposedtothemedicinehadlongerumbilical cords.Theysaidthattheincreasedcordlengthcouldbeexplainedby the increase offetalmovement caused by themedicine. Wright Dand ChanGM[10]studiedtherelationshipbetweenthebonemassof infantsandtheirumbilicalcordlengths.Theyfoundthatinfantswith ashortcordlengthhadlessbonestrengthandthattheﬁndingwas likelyduetodecreasedfetalmovement.

* Correspondingauthor.

E-mailaddresses:[email protected](E.Ryo),[email protected] (H.Kamata),[email protected](M.Seto),[email protected] (M.Morita),[email protected](K.Yatsuki).

http://dx.doi.org/10.1016/j.eurox.2019.100003

EuropeanJournalofObstetrics&GynecologyandReproductiveBiology:X1(2019)100003

ContentslistsavailableatScienceDirect

European Journal of Obstetrics & Gynecology and Reproductive Biology: X

j o u r n al h o m e p a g e : w w w . el s e v i e r . c o m / l o c a t e / e u r o x

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Therefore,fetalmovementseemstopromotecordlength.Onthe otherhand,alongercordmaygiveababymorefreedomtomove.

However,there havebeennoreportsthat demonstratea direct correlationbetween fetal movement andcord length in human beings.Thatisbecausetherehasneverbeenapracticalwaytocount fetalmovementsinmanyfetusesoverlongperiodsoftime.

We havedevelopeda fetalmovementaccelerationmeasurement recorder (FMAM recorder, http://e-mother.co-site,jp) that wasdesignedforhomeuse[11,12].Therecorderrecordsgrossfetal movementsbydetectingoscillationsof themother’sabdominal wall caused by fetal movements. In a previous study, we simultaneously observed gross fetal movements and maternal abdominalwall oscillationsrespectivelybyultrasonographyand theFMAMrecordertoexaminetheagreementsbetweenthetwo.

Theagreementsexpressedbyprevalence-adjustedbias-adjusted kappawere0.82-0.83 which meant almost perfect values [11].

Furthermore,usingtheFMAMrecorder,werecentlymadenormal referencevalues for gross fetal movement counts and demonstrated that the values are similar to those made using ultrasonography[12].The FMAMrecorder hasmade itpossible tocountgrossfetalmovementsovermanyhours.

The purpose of the current study was to examine the relationshipbetweenumbilicalcordlengthandfetalmovements ascountedbytheFMAMrecorder.

Materialsandmethods Countingfetalmovements

TheFMAMrecorderwasdescribedindetailinourpaststudies [12,13]. It weighs 290g and can be used at home. It has two accelerationsensors:oneisafetalmovementsensor(FMsensor), which attaches to the mother’s abdomen, and the other is a mother’smovementsensor(MMsensor),which attachestoher thigh.ThesensitivityoftheFMandMMsensorsis700mV/0.1G and120mV/0.1G,respectively.TheFMsensordetectsoscillations ofthemother’sabdominalwallcausedbygrossfetalmovements.

The recorderis unsuitable when themother moves frequently because the mother’s body movements themselves also cause oscillations.Thatis whytherecorder isused during hersleep.

However,themother doesmoveoccasionallyevenwhensheis asleep.Inprinciple,whentheMMsensordetectsnomaternalleg movementandtheFMsensordetectsoscillationsofherabdominal wall,grossfetalmovementsarejudgedtohaveoccurred.

Themotherswereaskedtorecordfetalmovementsduringtheir sleepweeklyorbiweeklyafter28weeks,becausetheaccuracyof

theFMAMrecorderislimitedbefore28weeks[11].Thedatawere uploadedtoaPC.Weacceptedrecordsonlywhendatacouldbe obtainedformorethan4hpernight.Therecordingwasdivided into10-stimeintervals(epochs),meaning360epochsperhour.All epochswerereviewedtodeterminewhetheranyfetalmovements occurredwithineachepoch.Anepochwithanyfetalmovements wasjudgedtobeonepositiveepoch.Thedecisionwasmadeusing a custom-made softwaresystem (Version 1.04A, NoruProLight Systems,Inc.TokyoJapan),whichwasdevelopedfortheFMAM recorder[12,14].Theratioofpositiveepochstoallepochsduring onenightwascalculatedasthemovementindex.

Subjects

Therewereatotalof62pregnantwomenwhocouldrecordfetal movementformorethan4hpernightanddeliveredababyatterm betweenFebruary2010andtheendof2016atTeikyoUniversity Hospital.Noneofthemothershadanymedicalcomplications,and noneofthebabieshadanyanomaliesorneurologicalproblems.

ThecharacteristicsofthemothersandbabiesareshowninTable1.

Methods

Afteralldelivery,thelengthoftheumbilicalcordwasmeasured afterseparatedfromthebaby.Thecordsegmentattachedtothe babywasleftroutinely3cminlength.Atrainedmidwifechecked cordabnormalitiesandmeasuredcordlengthusinga ruler.The lengthwasdeterminedasthenearestcentimetersandadded3cm inordertogetthetotallength.

First, the correlation between the cord length and the movementindexwasexamined.Inapreviousstudy,wereported thatthemovementindexdecreasesaspregnancyprogresses,with the decrease being relatively rapid around 32–35 weeks [12].

Therefore,therecordingsweredividedintothreegroupsbasedon gestationalweeks,i.e.28–31,32–35,and36–39weeks,andamean valueofthemovementindexwascalculatedforeachperiodper one woman. Multiple linear regression analyses were then conductedwithsixexplanatoryvariables(primipara/multipara, anterior / posterior locatedplacenta,placental weight, and the meanmovementindexvalueof28–31,32–35,and36–39week) andaresponsevaluable(umbilicalcordlength).

Next,allwomenweredividedintothreegroupsdependingon the cord length. The average umbilical cord length has been reportedtobearound55cm[2];therefore,whenthecordlength was 50–60cm, the women were classiﬁed in the middle cord group.Theshorteror longercordlengthgroupswerelessthan

Table1

Characteristicsofallwomenandthreegroupsdependingonthecordlength.

total groups

short middle long p

n 62 20 22 20

mother’sage 32.9 32.5 33.4 32.8 0.798

(20.0,44.0) (20.0,44.0) (25.0,41.0) (24.0,41.0)

BMI 21.1 21.4 20.4 21.5 0.327

(16.8,28.0) (17.6,28.0) (16.8,24.7) (17.8,26.8)

Para/non-para 20/42 8/12 9/13 3/17 0.138

anteriorlocatedplacenta(+/-) 18/44 4/16 8/14 6/14 0.516

deliveryweeks 39.2 39.0 39.1 39.4 0.649

(37.0,41.1) (37.3,40.9) (37.0,41.1) (37.1,41.0)

newbornweight(g) 2990.6 2853.6 3126.8 2977.9 0.067

(2340,3790) (2340,3404) (2396,3790) (2400,3576)

male/female 30/32 8/12 10/12 12/8 0.436

placentalweight(g) 573 525 594.3 595.3 0.070-1.000

(400.,790) (400,730) (420,785) (425,790)

Dataarepresentedasnumberormean(range).

ComparisonsamongthethreegroupswereconductedwithANOVAorTukey-Kramer.

2 E.Ryoetal./EuropeanJournalofObstetrics&GynecologyandReproductiveBiology:X1(2019)100003

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50cm and more than 60cm, respectively. Table 1 shows the characteristics of the three groups. Based on SD=10% and an expected10%movementdifference,wecalculatedasamplesizeof 16 women for each group with α=0.05 and 80% power. The numbersofwomenineachgroupwerebetween20and22.The indexofmovementwasthencomparedamongthethreegroupsby ANOVAforthethreegestationalperiods,i.e.28–31,32–35,and36– 39weeks.

Alldata was analyzed with JMPPro 12.0.1. The statistically signiﬁcantdifferencewassetatpvalueoflessthan0.05.

Thisstudywas approved bytheethics committeeof Teikyo University. All women gave written informed consent before participatinginthestudy.

Results

Atotalof2355.6hfrom368nightrecordswereavailableforthis study.Umbilicalcordlengthvariedfrom35to100cm.Themean length(10–90%)was54.8(39.6–69.7)cm.Therewerenoumbilical cordcomplications,suchasasingleartery,excessivetorsion,no torsion,orvelamentousinsertion.

Primipara and anterior located placenta were valuables to elongatecordlength(p=0.013,and0.015, respectively),andthe placentalweightalsohadpositiverelationshipwithcordlength (p=0.005);however,therewerenorelationshipsbetweenthecord lengthandthemovementindexof28–31,32–35,and35–39weeks (p=0.090,0.235,0.129,respectively).

Fig.1 shows thechanges in theindexof movements in the shorter,middle,andlongercordgroupsdependingongestational weeks.Inapreviousstudy,wereportednormalreferencevalues wheretheindexofmovementdecreasesaspregnancyprogresses, withthedecreasebeingrelativelyrapidaround32–35weeks[12].

Similarchangesareshownintheshorterandmiddlecordgroups;

however,thedecreaseseemstobeslightinthelongercordgroup.

Statistical comparisons also demonstrated that there were no differencesintheindexofmovementamongthethreegroupsat 28–31 and 32–35 gestational weeks (p=0.096, and 0.465, respectively);however,thelongercordgrouphadagreaterindex of movement than the other two groups at 36–39 weeks (p=0.0008).

Discussion

The factors determining umbilical cord length are largely unknown.MarpasP[15]reportedthatlittlecorrespondencewas foundbetweencordlengthandthefetalorplacentalweight.On thecontrary,GeorgiadisLetal.[16]reportedthatcordlengthwas associated withbirth weight, placental weight,and gestational age.Georgiadiaetal.alsoreportedthatgirlshadshortercords.

The results of this study demonstrated that there were no correlations found between the cord length at birth and fetal movementcountsafter28weeks;however,thelongercordgroup hadhigherfetalmovementcountsthantheothertwogroupsafter 36weeks.

Whatdidtheseresultsmean?Positivecorrelationsincludeboth thecordbecomesshorterandlongerdependingfetalmovement.

Simpleexplanationcouldbethatdecreasedfetalmovementdid not shorten the cord length but increased one elongated that.

Actually, there were no differences in the movement index betweentheshorterandmiddlecordgroupsintheresults.

InastudybyRichardLN[17],theauthorsnotedthatumbilical cords progressively grew longer toward term, and the rate of growthgraduallyslowed.Inanotherstudy,GeorgiadisLetal.[16]

alsofoundthatumbilicalcordsgrewprogressivelylongertoward term;however,thegrowthratewasgreatestbetween31and39 weeks, andthemaximum growthwas ataround 35–36 weeks.

Bothstudieswereconsistentthattheumbilicalcordcontinuedto growuntilterm.Continuinggrowofthecordseemedtorelateour study’sresultsthatthegroupwithlongercordshadhigherfetal movementcountsafter36weeksthantheother.

Wemadenormalreferencecurvesforfetalmovementsinour previous study [12] and demonstrated that fetal movements decreased at around32–35 weeks;however, theresultsofthis studyshowedthatthedecreasedfetalmovementsafterthatperiod couldbeanimportantfactorinﬁnallydeterminingwhetherornot theumbilicalcordbecomeslonger.

Looking at the changes in fetal movements based on the gestationalweeks shown inFig.1,we seethatfetal movement countsforthethreegroupswerenotsodifferentuntilaround32 weeks.Afterthat,decreasesinmovementinthelongercordgroup seemedsmallerthanthoseintheothertwogroups.Inthelonger cordgroup,asmallerdecreaseinfetalmovementsneartermmight make the umbilical cord longer and longer as pregnancy progresses,whichmighteventuallymakeasigniﬁcantdifference incordlengthbetweenthelongercordgroupandtheothertwo.

However,evenifthisistrue,itisstilldifﬁculttounderstand whytheshortercordgroupdidnotdemonstratelessmovement compared with the middle cord group. There are several limitations of this study. One limitation of studies about cord lengthisthatwecanmeasureonlyﬁnalcordlengthbutnotthe processofcordelongationduringpregnancy.Anotherlimitationis thatwecancountfetalmovementonlyafter28weekswhenthe cordlengthalreadybecomes2-thirdoffulllength.

Ontopofthat,animportantproblemofthisstudywasthatthe accuracyoftheFMAMrecorderhasnotbeenfullyconﬁrmed.We havediscussedabouttheaccuracyoftheFMAMrecorderinseveral previousstudies[11–14].Overall,therecorderhasagoodrecordof countingfetalmovements:however,additionalclinicalstudiesare still needed to fully conﬁrm its accuracy. If this study had demonstrated no positive results about relation between fetal movementsandcordlength,itwouldhavebeenunclearwhether theFMAMrecorderwasatfault orwhethertherewas trulyno relationship betweenthetwo. However,this studyshowed the positiveandreasonableresultthatthegroupwithlongerumbilical cordshadhigherfetalmovementcountsthantheothergroups.We feelthatthisstudyisonemorethatsupportstheaccuracyofthe FMAMrecorder.

Georgiadis L et al. [16] reported that girls seemed to have shortercords.Iftrue,thatraisesthequestionofwhetherfemale fetusesmovelesscomparedwithmalefetuses.Inapreviousstudy, wecomparedfetalmovementcountsbetweenboysandgirlsand foundnodifferencebetweenthetwo[12].

Inconclusion,thisstudysuggestedthatfetalmovementnear termisanimportantfactorindeterminingwhethercordlength becomesrelativelylongerinnormalpregnancies.

Fig.1.Changesinthemedianindexoffetalmovementinshorter(<50cm),middle (50–60cm),andlonger(>60cm)umbilicalcordgroups.Therewerenodifferences at28–31and32–35gestationalweeks(p=0.096,and0.465,respectively).The longercordgroupshowedmoremovementthantheothertwoat36–39weeks (p=0.0008).

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Funding

ThisworkwassupportedbytheJapanSocietyforthePromotion ofScience(GrantNumberJP16K10109).

Declarationsofinterest None.

Conﬂictofinterest

Theauthorshavenoconﬂictsofinteresttodeclare.

Acknowledgements

WethankProfessorTakuyaAyabeandMrs.MiekoFusefortheir support,andweappreciatelanguagehelpbyMr.HowardStacey.

Wealsoappreciatethecooperationofthewomenwhoparticipat- edinthisstudy.

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