328 SPO Abstracts

177 TRANSCEREllELLAR IlIAMETER IN TWIN GESTATIONS. Anna S Leung MD'. Bruce Kovacs MD". Jerry Yu MD-. University of Southern California, Los Angeles, California

Often there is a size discordance between the twins. This can be due to primary factors such as genetic differences or secondary to transfusion syndrome or intrauterine growth retardation. Previous studies using stand8.fd ultrasonographic biometry of biparietal diameter (BPD), abdominal circumference (AC) and femur length (FL) have begun to establish normative growth curves. Importantly however. the use of these measures often results in significant differences in the gestational age (GA) csli.natcs for co-twins. This is especially trouhlesome when ultrasongographic examinations arc performed late in the gestation. Therefore, in these circumstances the clinician is hampered in attempts to determine the precise GA. In order to address the prohlem of different BPD's in twins we sought to use another measure which would have good correlation with GA and which would he more consistent hetwccn co­twins. We performed a prospective, cross sC(;lional ultrasound examination on 43 well dated, uncomplicated twin gestations hetwccn 18 to 34 gestational weeks. The examination included measurements of transcerehellar diameter (TCO), BPO, AC and FL A statistically significant linear relationship was found hetween TCO and GA (R1 =0.91; P<O.OOOO) and a curvilinear relationship hetween BPD and GA (R'=0.94; P<O.OOOO) when the avc,age TCD and BPD hctwccn co­twins were used for analysis. GA was derived from either BPD using Hadlock formula or TCD using Goldstein's formula. When these calculated GA's were compared with the known GA's, there was a significant difference in GA estimates derived from the BPD and TCD (P=0.0126). The average difference in GA hetween co-twins using TeO was 4.4 days versus 8.9 days using BPO. In conclusion TeO is a useful measurement to estimate the GA more accurately when there is a difference in BPO between the co-twins.

178 ULTRASOUND PREDICTORS OF FETAL MACROSOMIA AND BODY COMPOSITION IN INFANTS OF DIABETIC MOTHERS

ill JS.rull.PM Catalano.MA Krew. S AminiX.A Thomas x ,L1 Mann MetroHeaith Medical Center. Cleveland Ohio

The purpose of this study was to prospectively analyze which ultrasound(US) parameters are most predictive of fetal macrosomia in infants of diabetic mothers(IDM);and to estimate whether fetal fat or lean body mass was increased in macrosomic(MAC)versus nonmacrosomic(NMAC) IDM and whether this could be determined using US. 34 women with gestational diabetes (n=25) and insulin dependent (n=9) women were prospectively examined in the third trimester. US measurements include BPD. HC,FL, abdominal circumference (AC).transcerebeliar diameter, kidney and liver length,SC abdomen and thigh fat.Each subject had at least 3 US's performed a minimum of 3 weeks apart.Each neonate had skinfold measurements and total body electrical conductivity (TOBEC) to estimate body composition.MAC was defined as birthweighb90% and NMAC was defined as <90% for gestational age(EGA).Twelve(38%) IDM were MAC and 22(62%) were NMAC and EGA at delivery was similar.MAC 37.6±1.4 NMAC 38.1±t.4wks p=.30.The overall mean growth rate of US measurements were compared using a Wilcoxon rank sum.There was a significant increase in AC,(mean±SD)MAC 12.2±2.0 NMAC 10.0±2.3mm/wk p=.02.SC abdomen fat,MAC 0.41 ±0.15 NMAC 0.22±0.16mm/wk p=.006.thigh fat.MAC 0.35±0.01 NMAC O.19±0.t8mm/wk p=.OII.and liver length MAC 3.1±t.2 NMAC 1.9±0.92mmiwk P=.OI in the MAC as compared with the NMAC US measurements. In addition to birthweight,MAC 3874±334 NMAC 3070±420 p=.0001,MAC infants also had significantly greater skinfold measurements,MAC 12.5±2.3 NMAC 9.4±1.8 p=.0001 ,% body fat MAC 17.2±4.1 NMAC 10.8±4.2 p=.0002,and lean body mass.MAC 3215.l;146 NMAC 2726±345 p=.0001.0ur results support previous findings that AC growth is predictive of MAC in IDM.Furthermore. the increase in AC appears to be secondary to an increase in both fetal fat (SC fat) and lean body mass (liver).Supported by NIH RR-0021 0 and 22965.

January 1992 Am J Obstet Gynecol

179 A IIEII ALGORIT ... FOR RISK ASSESSIIENT OF DIABETES-ASSOCIATED COFlICATlCltS DlIRIIG PREGIrIAlICY: E.A. Reece, G. Francisx , Z. Hagay", Departments of Ob/Gyn at Tet1l'le University School of Medicine, Philadelphia, PA and Yale University School of Medicine, New Haven, CT

180

Classification schemes have fai led to provide measurable means for prospective risk assessment of diabetes-associated c~L ications making peri conceptional counsel ing vague and iFJ1)recise. This study was undertaken to create mathematical modeLs' using both pre-pregnancy and intra-pregnancy conditions to quantitatively predict a patient's relative risk for adverse maternal and fetal outcome. The study population included 361 gestational diabetics (GOM), 205 uncoq:>l ieated pre-gestational diabetics (P·GDM), 82 c"""l icated P·GDM, and 150 controls. Multivariate analysis was used to determine a patient's overalL relative risk for a given outcome. A model was derived based on whether the variable was dichotomous or continuous. All the individual fJ values were entered into an eaua~;on:bFo~ ) dichotomous variables, the overall RR = e~DI i + 2. 2.. + .•.. For continuous variables, the predicted outcome = C1+b

1Xl + bZX

Z + •.. ) where I is a constant representing the intercep calculated during the nultivariate analysis; bt = beta value for first independent variable; Xl = actual value for first independent variable in model. For exaf11lle, the relative risk for fetal distress can be assessed prior to pregnancy or during pregnancy as follows:

Model I (Pre-Pregnancy Conditions)

RISK FOR FETAL DISTRESS Model II

( Intra-Pregnancy Condi t ions)

duration: RR;1.06/yr Proteinuria: RR;1.92 HBP: RR;1.8 Late HTN: RR;2.2 Gravidity: RR;1. t8

Model III (Pre- and Intra­Pregnancy Cond.)

duration: RR;1.06/yr Proteinuria: RR=1.7 Gravidity: RR;0.8

awCLUSIOl: This new algorithm provides for the first time a measurable aoo thus useful means of estimating possible fetal and/or maternal cOOPt ications that may arise during the antepartln or peripartun periods.

THE POSITIVE PREDICTIVE VALUE OF A SIlIIOGRAPHIC DIAGIIOSIS OF FETAL IlACROSaIIA. Raphael N. Pollack', Michael Y. Divon, Dept. Ob/Gyn, The Albert Einstein College of Medicine, Bronx, NY.

The positive predictive value (PPV) of the sonographic diagnosis of fe-tal macrosomia was prospectively evaluated in 519 pregnancies of > 41 weeks gestation examined within 1 week of del ivery. Estimated fetal weight (EFU) was obtained using measurements of abdominal circLl1lference and femJr length and the table of Hadlock et al. The PPV of varying sonographic EFUs in predicting birthweights of ~4000 and ~4500 grams, respectively, is shown:

ut trasound EFU Probabi l i ty of Actual BW (Gms.) >4000 Gms. >4500 Gms.

3500 36% 7% 3600 40% 8% 3700 44% 9% 3800 49% 11% 3900 56% 14% 4000 66% 17% 4100 70% 19% 4200 71% 20% 4300 75% 2t% 4400 80% 26% 4500 83% 29% 4600 80% 20% 4700 86% 29%

Ue conclude that the PPV of a sonographic diagnosis of macrosomia increases with increasing EFW. 75% of fetuses with an EFW of 4300 grams or Larger will indeed be macrosomic by birthweight criteria.