323 BINDING OF BILIRUBIN TO ALBUMIN IN FETAL BLOOD AND AMNIOTIC FLUIDS. A. PASMAN1, D. OEPKES1, F. P. H. A. VANDENBUSSCHE1, 1Leiden UniversityMedical Center, Dept. of Obstetrics, Leiden, Netherlands

OBJECTIVE: The bilirubin concentration in amniotic fluid has been used topredict the severity of fetal anemia since 1961. However the factors determin-ing that concentration are unknown. Because unconjugated bilirubin (UB), themain bilirubin configuration in the fetus, is tightly though reversibly bound toalbumin, our hypothesis is that UB divides equally over the albumin in all fetalextracellular compartments.

STUDY DESIGN: Amniotic fluid and fetal blood samples were obtainedbefore the first intrauterine transfusion, in 32 nonhydropic and 13 hydropicfetuses, with gestational ages ranging from 19 to 35 weeks. UB and albuminwere measured in blood and in amniotic fluid.

RESULTS:

In nonhydropic and mildly hydropic fetuses the correlation between thebilirubin/albumin ratio in fetal blood and amniotic fluid was significant (R2=0.98, p!0.001).

CONCLUSION: Amniotic fluid bilirubin concentration is determined by thebilirubin concentration in fetal blood and by the albumin concentrations infetal blood and amniotic fluid.

324 ANALYSIS OF LEPTIN CONCENTRATION AND A FETAL LEPTIN GENE POLYMOR-PHISM IN MID-TRIMESTER AMNIOTIC FLUID: ASSOCIATION WITH MATERNAL,FETAL AND OUTCOME PARAMETERS MLADEN PREDANIC (F)1, SRIRAM C. PERNI1,CLAUDEL JEAN-PIERRE1, STEVEN S. WITKIN1, 1Weill Medical College of CornellUniversity, Obstetrics and Gynecology, New York, New York

OBJECTIVE: Leptin, a protein associated with energy homeostasis, is pre-sent in amniotic fluid (AF). To assess the origin of AF leptin and its influenceon fetal growth and pregnancy outcome, we evaluated associations betweenmid-trimester AF leptin concentrations, a fetal leptin gene polymorphism andmaternal and fetal parameters.

STUDY DESIGN: Mid-trimester AF was obtained from 154 women between18-20 weeks gestation. Leptin concentrations were determined by ELISA.DNA from AF-derived cells was analyzed for a GOA polymorphism atposition �2548 in the leptin promoter by polymerase chain reaction andendonuclease digestion. Neonatal and maternal variables, placental weight andoutcome data were obtained after completion of laboratory testing.

RESULTS: The median (25th-75th percentile) AF leptin concentration was8.1 (0.7-61.5) ng/ml. The AF leptin level was positively correlated withmaternal BMI (P = .01) and negatively associated with parity (P=.04). Incontrast, there were no associations between AF concentration and fetal orplacental birthweights. The AF leptin level was not associated with maternalage, ethnicity, fetal gender, preterm birth, preeclampsia or chorioamnionitis.The fetal leptin genotype distribution was 38.6%G, G, 41.2% G, A and 20.2%A, A. Maternal BMI or median AF leptin levels were unrelated to the fetalleptin genotype. There was a lower prevalence of A, A homozygotes inpregnancies ending in preterm birth (7.7%) than in term births (20.0%), butthis did not reach statistical significance.

CONCLUSION: The association between mid-trimester AF leptin concen-tration and maternal BMI and parity strongly reinforce that AF leptin isderived primarily from the mother. These maternal-derived fluctuations inAF leptin concentrations do not influence neonatal birthweight or pregnancyoutcome.

325 THE RELATIONSHIP BETWEEN OLIGOHYDRAMNIOS AND PERINATAL OUTCOMESMOON RYEONG RHEE1, HYUN JUNG CHO1, JUNG MI OH1, OK RYONG LIM1, EONAH KIM1, SANG SHIN PARK1, HA JUNG LIM1, 1Mizmedi Hospital, Departmentof Obstetrics and Gynecology, Seoul, South Korea

OBJECTIVE: The purpose of this study was to determine whether oligohy-dramnios (AFI %5cm regardless of gestational age) predicts poor perinataloutcomes.

STUDY DESIGN: We identified all women who visited our institution fromJanuary 2004 to June 2005 in whom oligohydramnios was diagnosed withoutrupture of membrane by antenatal ultrasound. 117 women had been diagnosedas oligohydramnios without rupture of membrane. All women with oligohy-dramnios were admitted to the hospital for labor induction in spite of reactiveNST findings. Each of the women was compared with patients withAFIO5cm. Case patients were matched with control patients for maternalage, parity, and gestational age. Statistical analysis was performed using a chi-sqaure test, Fishers exact test, or a Student t-test. As for the adjustment ofother factors, we used a linear or logistic regression analysis.

RESULTS: 117 women with oligohydramnios were compared with 117control subjects. There were statistically significant differences between 2groups in the rate of cesarean section (p=.004), the rate of cesarean section fordistress(p=.007), fetal birth weight(p=.004), and duration of stay in NICU(p=.022). We were unable to find any differences in the risk of meconiumstaining, FHR deceleration (such as variable, late or prolonged deceleration),5-minute Apgar score, or abnormal NST results. After adjusting for birthweight, there was no statistically significant difference in duration of stay inNICU(p=.142), but there were still clinically significant differences in the rateof cesarean section(OR 2.280, 95%CI 1.275-4.080) and the rate of cesareansection for distress(OR 3.964, 95%CI 1.256-12.516).

CONCLUSION: Pregnancies with oligohydramnios appear to carry perinataloutcomes similar to those without oligohydramnios, except for the rate ofcesarean section and the rate of cesarean section for distress. This studysupports the assertion that AFI is a weaker predictor of poor perinataloutcomes than has been classically suggested.

326 ULTRASOUND ACOUSTIC OUTPUT DURING THIRD TRIMESTER BIOPHYSICALPROFILE EYAL SHEINER (F)1, HOWARD T. STRASSNER1, MICHAEL J. HUSSEY1,XAVIER POMBAR1, JACQUES S. ABRAMOWICZ1, 1Rush University Medical Center,Ob/Gyn, Chicago, Illinois

OBJECTIVE: Diagnostic ultrasound (DUS) has the potential for bioeffects,mainly temperature elevation and cavitation of gas bubbles, expressed,respectively, by the Thermal Index (TI) and Mechanical Index (MI). Sincefetal lungs and bowels do not contain gas, the mechanical risk is probablynonexistent. The biophysical profile (BPP) involves static, relatively prolongedscanning. Bones have high levels of energy absorption. Thus, there may beconcern of temperature elevation in their vicinity. However, no human clinicaldata exist regarding fetal exposure. The present study was aimed at examiningthe acoustic output of clinical ultrasound instruments, as expressed by TI andMI, during routine third trimester BPP testing.

STUDY DESIGN: A prospective observational study was conducted inpatients undergoing third trimester BPP scans (iU22, Philips Medical Sys-tems). Color and spectral Doppler were not included. Data were collected byan obstetrician. Sonographers were unaware of the data being sought. Dataincluded gestational age, duration of the exam, and specific time durationspent at each MI and TI. Each MI and TI variation was recorded during theexam. Statistical analysis was performed using the SPSS-12 package (SPSS,Chicago, IL).

RESULTS: Ninety-one TI and MI variations during 30 BPP examinationswere evaluated. Mean gestational age was 34.0G 3.7 weeks. Mean duration ofDUS was 12.8G 4.0 minutes. During the examinations the mean TI was0.3G0.1 (range 0.2-0.7) and mean MI was 1.1G0.1 (range 0.7-1.2). The highestTI (0.7) recorded lasted for two minutes.

CONCLUSION: The risk of fetal exposure to an increase in temperatureduring routine third trimester BPP exams, as expressed by TI, is extremely low,and probably lacks clinical significance.

S100 SMFM Abstracts