499 INTENSIVE FETAL SURVEILLANCE IN THE FIRST 12 HOURS FOLLOWING LASERTREATMENT IN TTTS MASAMI YAMAMOTO1, MOHAMMED ESSAOUI2, MALEKNASSAR2, YVES VILLE3, CAS-HPH Universidad del Desarrollo, Santiago, Chile,CHI Poissy St Germain en Laye, Obstetrics and Gynecology, Poissy, France,CHI Poissy-St Germain, Poissy, France

OBJECTIVE: To evaluate closely the twins after laser, and to try to find outwhich were the patterns of abnormal Doppler and abnormal Urine Production(UP) that led to fetal demise.

STUDY DESIGN: 11 consecutive TTTS cases were evaluated before and up to12 hours after laser, every 2. Umbilical artery (UA), Middle cerebral artery(MCA), Ductus Venosus (DV) and UP were evaluated. End diastolic flow, Awave and PSV below 1.5 MOM were considered normal. The parameters wereclassified as stable abnormal or normal if they did not changed during theevaluation, and worsening or improving if they changed from the preoperativeevaluation. UP was considered improving when the recipient (R) decreased tothe half and the donor began urination. All conclusions were analyzed togetherto describe a pattern of abnormal parameter that could explain fetal demise.

RESULTS: 5 pairs of twins survived: Doppler were normal in 3 before andafter laser, with UP normalization in R and D. Another case had the sameevolution but for the Donor (D) which did not present UP within 12 hours. Inthe fifth case, absent end diastolic flow in the UA of the D remainedunchanged for 12 hours. Two pairs of twins had double fetal demise within 3days following laser. The Doppler parameters were unchanged for 12 hours inone and MCA-PSV increased in the D in the other, with persistently high UPin the recipient, and absent UP in the D. These could be considered aspersistence of TTTS. One case showed high MCA-PSV with severe anemia inthe D and UP normalization in the R. This was considered as feto-fetalhemorrhage that was managed with cord coagulation of the donor. Finally, 3cases presented with the demise of the D within 3 days preceded by worseningof UA Doppler in one, of MCA-PSV in one, and of both parameters in onecase.

CONCLUSION: Fetal demise within 3 days post-laser was preceded bydeterioration in UA or MCA Doppler or persistence of abnormal UP inrecipients over the first 12 hours. These are likely to be related to either acutefetal anemia, placental insufficiency or persistent TTTS.

500 ASSESSING FETAL URINE PRODUCTION USING THREE DIMENSIONAL ULTRA-SOUND. REPRUDCIBILITY STUDY AND CHANGES IN TWIN-TO-TWIN TRANSFUSIONSYNDROME TREATED BY LASER YUICHIRO TAKAHASHI1, RENATO MOREIRA DESA2, MASAMI YAMAMOTO3, YVES VILLE2, 1CHI Poissy-St Germain, Poissy,France, 2Universite Paris Ouest SQY-V CHI Poissy St Germain en Laye,Poissy, France, 3CAS-HPH Universidad del Desarrollo, Santiago, Chile

OBJECTIVE: Fetal urine production in TTTS is a reflection of hemodynamicimbalance between donor and recipient twins. To evaluate changes in fetalurine production following laser therapy.

STUDY DESIGN: Urine production rate (UPR) was measured using 3Dultrasonography with virtual organ computer aided analysis (VOCAL TM).The rotation angle was set at 30 degrees. UPR was calculated using thefollowing formula: (V2(ml) - V1(ml)) ! 60 (min)/interval (min), where V1 isthe first measurement of the bladder volume in filling cycle and V2 is thesecond. UPR was measured together with total umbilical venous flow (TUVF)(ml/min) before and after treatment in cases of severe TTTS treated by laser.

RESULTS: UPR and TUVF were measured in 23 cases (107 measurements)in Donors (D) and Recipients (R). Intra-operator and inter-operator mea-surements were 88% and 91% within limits of agreement. There was asignificant correlation between TUVF and UPR (r=0.5, p!0.0001). Beforelaser treatment, UPR and TUVF were significantly higher in R than in D.UPR increases with gestational age in the recipient (r=0.57, p=0.01) only.Following laser, when both twins were alive and TTTS had resumed, thecorrelation was found in both twins (D, r=0.57, p=0.0002; R, r=0.55,p=0.0003). The UPR R/D ratio [(R UPR/kg – D UPR/kg)/ R UPR/kg]decreased significantly following laser (p=0.026) in 8 cases prospectively.Among 57 cases of severe TTTS, the bladder was not visible in 21 whichnevertheless showed a positive UPR which to correspond to an 17% falsepositive rate in 12.6 minutes interval of measurements.

CONCLUSION: UPR can be easily and reliably assessed by 3-D ultrasound.Changes in UPR were more accurate than bladder visualization to reflectanuria in the D and preoperative staging of TTTS should be re-assessed usingthis technique in a larger series. UPR was a mere reflection of TUVF inagreement with the hemodynamics of donor and recipient twins. Fetal UPRmight also be useful to evaluate early the effect of laser treatment in TTTS.

501 ANTENATAL NON-INVASIVE MANAGEMENT OF NEONATAL ALLOIMMUNE THROM-BOCYTOPENIA YOAV YINON1, MAYA SPIRA1, ETTY DANIEL-SPIEGEL2, ELIEZERSHALEV2, BENJAMIN CHAYEN1, EYAL SCHIFF1, SHLOMO LIPITZ1, 1Sheba MedicalCenter, Tel Aviv University, Obstetrics and Gynecology, Tel-Hashomer, Israel,2Ha’Emek Medical Center, Obstetrics and Gynecology, Afula, Israel

OBJECTIVE: Alloimmune thrombocytopenia is a serious fetal disordercaused by platelet antigen incompatibility between the mother and fetus. Theaim of this study was to evaluate a non- invasive management of alloimmunethrombocytopenia, in which treatment included only blind administration ofimmunoglobulin.

STUDY DESIGN: 17 women with 30 pregnancies at risk of neonatalalloimmune thrombocytopenia, and in which the fetuses were all antigen-positive, were included. Except for six cases, where the women refusedtreatment, 24 pregnancies were managed by a weekly administration ofimmunoglobulin without monitoring platelet counts, and repeated ultrasono-graphic examinations for signs of intracranial hemorrhage. The treatmentstarted in the 18-24 gestational week and was continued until delivery. In fourpregnancies a predelivery fetal blood sampling was performed in order todetermine the mode of delivery.

RESULTS: All fetuses were delivered by elective cesarean section, except fortwo cases, in which vaginal delivery was achieved, after confirming a fetalplatelet count above 50000. The mean platelet count at birth after treatmentwas 117,000 (range 11,000-320,000), compared to 17,000 (range 8000-70,000)among the 17 first affected siblings and 24,000 (range 10,000-44,000) amongthe 6 infants whose mothers refused treatment (p!0.05). Only 8% (2/24) ofthe treated fetuses had platelet counts of less than 30,000 at birth compared to74% (17/23) of the untreated siblings (p!0.05). None of the treated and non-treated fetuses had an intracranial hemorrhage.

CONCLUSION: Non-invasive management of alloimmune thrombocytope-nia consisting of only immunoglobulin administration is highly effective andseems safe. Therefore, the value of performing cordocentesis and platelettransfusion is doubtful in view of its risk for the fetus, and the fact thatimmunoglobulin therapy so effectively improves the fetal platelet count.

502 WITHDRAWN

503 THE USE OF TRANSVAGINAL ULTRASOUND FOR THE DIAGNOSIS OF PREMATURERUPTURE OF MEMBRANES TARA BECKER (F)1, JOHN HOBBINS1, 1University ofColorado Health Sciences Center, Obstetrics and Gynecology, Denver,Colorado

OBJECTIVE: To determine whether transvaginal ultrasound (TVUS) can beused accurately to diagnose intact versus ruptured membranes (ROM).

STUDY DESIGN: This pilot observational study involved 3 groups: I) 47patients known to have intact membranes, II) 42 patients known to haveROM, and III) 31 patients reporting leakage of fluid upon admission with anunclear initial diagnosis. All three groups underwent TVUS to assess theintegrity of the fetal membranes crossing over the cervix. Group III underwentTVUS prior to a speculum exam performed to look for pooling, fluid leakageupon Valsalva, nitrazine, and ferning.

RESULTS: Membranes were visualized in 93.6% (44/47) patients known tohave intact membranes (Group I). In the 3 remaining patients, the posteriorposition of the cervix precluded ideal visualization. Membranes were nevervisualized over the os in Group II patients (0/42). In Group III, TVUS findingscorrelated with the ultimate clinical diagnosis in 93.5% of patients. Thirteenpatients were found to have ROM by speculum exam, and of these, 12 (92.3%)had no identifiable membranes. In the remaining case, membranes were clearlyruptured 48 hours later. In the 16 patients found to have negative ROM,

SMFM Abstracts S145