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Læknablaðið - 15.11.1987, Síða 16

Læknablaðið - 15.11.1987, Síða 16
368 LÆKNABLAÐIÐ NÝR DOKTOR í LÆKNISFRÆÐI - REYNIR TÓMAS GEIRSSON Fyrir nokkru varði Reynir Tómas Geirsson doktorsritgerð sína sem heitir Intrauterine volume in pregnancy. Hér fer á eftir útdráttur úr retgerð hans: Intrauterine volume, a three dimensional measure of growth, was evaluated in pregnancy. The ultrasonic method for measurement of volume was investigated for accuracy and error potentials and then used to collect information on the growth of three volume components, total intrauterine (IUV), intraamniotic (IAV) and placental volume (PLAV), in the latter half of normal pregnancy. Against reference standards from the normal population, two other main groups, a nonselected and a preselected high-risk group were studied, to test the hypothesis that a small intrauterine volume would predict the presence of a small-for-dates and possibly compromised baby. In a phantom model situation a method based on serial paralell planimetric area (PPA) measurements was significally more accurate than a linear measurement method used by previous authors. With the former method 93.3% of measurments were within 5% of the true volume (mean error 0.43%). Accuracy in vivo was evaluated in 14 women undergoing midtrimester termination and in eight women delivering near term. High correlation between ultrasonically and directly/indirectly measured IAV was shown. Therefore the same level of accuracy could be expected in pregnancy as in the phantom models. Intraand interobserver variation was small. The PPA method was used for all measurements in pregnancy. Data from 115 healthy women with no pregnancy complications were evaluated longitudinally to study normal growth and derive reference standards. Median and mean values of IUV increased from around 1000 ml at 20 weeks to 4500 ml at 40 weeks, IAV from 700 to 3400 ml and PLAV from 260 to 800 ml during the same times. The standard deviation was large for all volumes at any stage of pregnancy. The rate of volume increase was near constant for IUV and IAV, except during the 30-35 week period when a faster rise was observed. PLAV growth decreased after 30 weeks. With growth of IUV and IAV following a largely linear trend, a tendency for ranking of volume levels was observed. Predictability of one measurement on the basis of earlier ones weakened with increasing separation of time points. In a non-selected antenatal population of 362 women having measurements at around 32 and for most also at 36 weeks, the efficacy of volume, fetal biparietal and abdominal area (AA) measurements of = < lOth centile in predicting birthweight of = < lOth and = <3rd centiles was evaluated. IUV showed the highest sensitivity in predicting both birthweight categories, but a higher number of false positive tests resulted in a lower predictive value of positive test (mean 34% for babies weighing = < lOth centile) and a higher at risk group than found for AA measurements (mean 54%). IAV, PLAV and BPD had poorer predictive values than IUV or AA. In a preselected high-risk population of 130 women with a 30% prevalence of small-for-dates babies, AA and IUV had the highest sensitivity and positive predictive values. Higher sensitivity of IUV at earlier gestations was a diagnostic advantage. For screening purposes AA measurements were more suitable. Several more maternal and fetal variables, including smoking, were not or only weakly correlated to intrauterine volume components. Volumetric growth in twin pregnancies and pregnancies complicated by diabetes or hydramnios was described. Maximum distension of the uterus measured amounted to 8386 ml. A link between volume levels and blood sugar control was demonstrated.

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