The incidence and clinical characteristics of placental insufficiency among high-risk pregnancies with normal umbilical artery resistance index after 32 weeks gestation : a cross-sectional study

Van der Merwe, Elrike (2015-12)

Thesis (MMed)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: Introduction: Intrauterine fetal growth restriction (FGR) due to placental insufficiency (PI) is an important cause of perinatal morbidity and mortality. There is also evidence that FGR is associated with neurodevelopmental delay, as well as the development of insulin resistance, obesity, hypertension and diabetes mellitus type 2 as an adult. It is therefore of the utmost importance to develop surveillance strategies and management protocols to reduce the incidence of FGR or, failing that, improving their outcome. Traditionally fetal wellbeing in suspected SGA was assessed by umbilical artery Doppler (UAD) resistance index (RI) or pulsatility index (PI) and if found to be within the normal range, it was seen as a reassuring sign that no significant placental disease is present. However, studies have shown that the pathophysiology of early- and late onset FGR are different and that late onset placental insufficiency (LOPI) may be present even in the presence of a normal umbilical artery Doppler result. The aim of this prospective study was to determine the incidence of LOPI in high risk women with a normal UA RI and assess which clinical variables are associated with this. Method: The study was a prospective, descriptive study conducted from 11 February 2013 till 21 October 2013 at Tygerberg Hospital (TBH), a secondary and tertiary referral centre in the Western Cape Province, South Africa, responsible for the Eastern half of the Cape Town Metropole and surrounding areas. The study population consisted of all women referred by the clinical (nursing or medical) staff to the Fetal Evaluation Clinic (FEC) or ultrasound unit at TBH for UA RI assessment according the current Western Cape Ultrasound policy. Exclusion criteria included known fetal anomalies, multiple pregnancies and proven pre-eclampsia. Recruited patients received an ultrasound examination by senior staff and the ultrasound data were captured in Astraia© database. Based on the ultrasound data the women were divided into 4 subgroups for comparison. Results: A total of 228 patients were recruited. Eight were excluded from the study for various reasons (incomplete consent (2), no ultrasound data (3), too early GA after redating (2), known LOPI at time of recruitment (1)). In 10 cases fetal anomalies were noted on ultrasound and these were also excluded – 6 of these had evidence of late onset placental insufficiency and 4 were small for gestational age. This left 210 study participants for the final analysis, with 76 classified as likely LOPI (36.2%) and 134 in the non LOPI group (63.8%). The likely LOPI group was equally divided with 38 (18%) patients each in the average for gestational age (AGA) and small for gestational age (SGA) groups. In the normal placenta group the majority of patients (112 (53%)) were AGA with 22 (11%) being SGA. There were no clinically significant differences between the groups when the baseline characteristics, Doppler and non-Doppler findings were compared. Conclusion: LOPI is a condition that affects a significant proportion of our population. This does not only have consequences for the short term pregnancy outcome, but also for the long term outcomes, with regards to neurodevelopment and the development of metabolic diseases. In settings where pregnancy dating is far less accurate than in developed countries and where customised growth charts are not available, it may not be appropriate to base management algorithms on the expected fetal weight (EFW) centile as inaccurate clinical or relatively late ultrasound dating (after 20 weeks) may not have allowed the EFW to drop below the 10th centile for the assumed (and perhaps underestimated) gestation. This study shows that relying on a distinction between AGA and SGA would seriously underestimate the magnitude of the problem of placental pathology and also illustrates the poor sensitivity of traditional clinical risk factors and grey scale ultrasound findings in identifying the pregnancies at risk of LOPI-associated complications. Further studies are needed to assess feasibility and impact of the proposed policy change.

AFRIKAANSE OPSOMMING: Inleiding: Intrauterine fetale groei beperking (FGR) as gevolg van plasentale ontoereikendheid (PI) is 'n belangrike oorsaak van perinatale morbiditeit en mortaliteit. Daar is ook bewyse dat FGR geassosieer word met neurokognitiewe abnormaliteite, sowel as die ontwikkeling van insulienweerstandigheid, vetsug, hoë bloeddruk en diabetes mellitus tipe 2 as 'n volwassene. Dit is dus van die uiterste belang om toesig strategieë en behandeling protokolle te ontwikkel om die voorkoms van FGR te verminder, of indien nie,`n verbetering in die uitkoms bewerkstellig. Tradisioneel is fetale welstand beoordeel deur umbilikale arterie Doppler (UAD) weerstands indeks (RI) of pulsatiliteits indeks (PI).Indien dit binne normale perke bevind word , is dit gesien as 'n gerusstellende teken dat geen beduidende plasentale siekte teenwoordig is. Studies hetegter getoon dat die patofisiologie van vroeë- en laat aanvang FGR wel verskil en dat laat aanvang plasentale ontoereikendheid (LOPI) teenwoordig kan wees selfs in die teenwoordigheid van 'n normale UAD. Die doel van hierdie studie was om die voorkoms van LOPI in 'n groep hoë risiko vroue met `n normale UA RI te bepaal en te evalueer watter kliniese veranderlikes daarmee verband hou. Metode: Die studie was 'n prospektiewe, beskrywende studie wat vanaf 11 Februarie 2013 tot 21 Oktober 2013 by die Tygerberg Hospitaal (TBH), 'n sekondêre en tersiêre verwysing sentrum in die Wes-Kaap Provinsie, Suid-Afrika, wat verantwoordelik is vir die Oostelike helfte van die Kaapstad Metropool en omliggende gebiede. Die studie kohort het bestaan uit al die verwysings deur kliniese (verpleging of mediese) personeel na die Fetale Evaluering Kliniek(FEC) of ultraklankeenheid by TBH vir UA RI assessering volgens die huidige Wes-Kaap verloskunde ultraklank beleid . Uitsluitingskriteria het pasiënte met bekende fetale abnormaliteite, meervoudige swangerskappe en pasiënte bekend met pre-eklampsie ingesluit. Gewerfde pasiënte het`n ultraklank ondersoek deur senior personeel in die sonar department ontvang . Die ultraklank data is opgeneem in die Astraia© databasis. Gebaseer op die ultraklank data is die pasiënte in 4 subgroepe verdeel vir vergelyking. Uitslae: 'n Totaal van 228 pasiënte is gewerf. Agt pasiente is as ontoepaslik beskou en is nie in die studie ingesluit nie. ‘n Verdere 10 pasiënte het fetale kongenitale abnormaliteite gehad en was ook uitgesluit- 6 het bewys van laat aankoms plasentaleontoereikenheid gehad en 4 was klein vir hulle swangerskapsduurte.Dit het 210 studie deelnemers vir die finale analise oorgelaat, met 76 geklassifiseerd as waarskynlik LOPI (36,2%) en 134 in die nie LOPI groep(63,8%). Die waarskynlike LOPI groep het gelyke getalle gehad in elke groepmet 38 (18%) pasiënte elk in die gemiddelde gestasie-ouderdom(AGA) en klein vir gestasie-ouderdom (SGA) groepe. In die normale plasenta groep is die meerderheid van die pasiënte (112 (53%)) AGA met 22 (11%) SGA. Daar was geen klinies betekenisvolle verskille tussen die groepe toe die basislyn eienskappe, Doppler en nie-Doppler bevindings vergelyk is. Gevolgtrekking: LOPI is 'n toestand wat 'n betekenisvolle deel van ons bevolking affekteer. Dit beteken nie net gevolge op die kort termyn vir die swangerskap nie, maar ook in met betrekking tot neurokognitiewe ontwikkeling en die ontwikkeling van metaboliese siektes. In `n kliniese omgewing waar swangeskapsdatering dikwels nie akkuraat is, en waar daar nie persoonlike groeikaarte beskikbaar is nie, is dit dus baie maklik om die geskatte fetale massa en sonar meetings verkeerd te interpreteer en sodoende SGA en LOPI te mis. Hierdie studie toon dat die vertroue op 'n onderskeid tussen AGA en SGA die omvang van die probleem ernstig sou onderskat . Dit illustreer ook die swak sensitiwiteit van tradisionele kliniese risiko faktore en swart en wit ultraklank bevindinge in die identifisering van die swangerskappe wat in gevaar is vir die risiko van LOPI-verwante komplikasies .Verdere studies is nodig om die haalbaarheid en die impak van die voorgestelde beleids verandering te evalueer.

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