416 SPO Abstracts

516 A fOUR YEAR fOllOW-UP Of HEARING AND NEURO­DEVELOPMENT IN CHILDREN EXPOSED IN UTERO TO VIBROACOUSTIC STIMULATION

By Westgren M, Nyman M, Barr M, Dept Obstet GynecoI KaroIinska Institutet Huddinge University Hospital, Sweden

Several investigators have expressed concerns about exposing the fetus to VA stimulation we found it therefore essential to study the long-term effect.

A total number of 525 children were included in the present study. All children had been followed according to the routine Swedish health care program. At 4 years of age an extensive examination is performed including an auditory test (250-8,000 Hz). Results: In this material two children had hearing defects (otosalpingitis, hereditary). Eight children were disabled, but no handicap could be related to the VA stimulation. Discussion: This study does not provide any evidence that VA stimulation should be associated with an increased risk of neuro­developmental disorders nor impaired hearing.

517 POSlllONOF THE VIBRoACOUSllCSllMULATORDOES NOT AFFECT FETAl RESPONSE.IZ..EJIIL RB Ne'M1lln, L.JoI1naonlC • Madlcallkllverslty of sc, ClJarle8ton, sc.

The fetal vibroacoustic stimulation test (VAST) has become an established adjunct to the nonstress test (NST) for assessment of fetal well-being. However, pos~ioning of the stimulator over the fetal vertex was empirically selected with little consideration for alter­natives.The optimal placement of the vibroacoustic stimulator has not been established. Gerhardt measured extremely intense sound pressures (135 dbs) when an electronic artHicial larynx (EAL) was applied directly over the fetal ear in pregnant ewes (AJOG1988; 159: 228-32). Sound pressures decreased as the distance from the EAL increased. The following study prospectively evaluated the fetal response to stimulation randomly applied over the fetal vertex or breech. The parameters evaluated include fetal heart rate (FHR) reactivity, fetal movement (FM) and fetal startle. Between December, 1990 and May, 1991,205 patients with a nonreactive NST after ten minutes were prospectively randomized to receive VAST (Coro­metrics Model 145) over the fetal vertex (n#110) and over the fetal breech (n=95). Both groups were similar w~h respect to maternal age, gestational age, and indication for NST. A subset of 49 patients (2~ breech and 25 vertex) was evaluated for a change in FM w~h VAST as recorded by a doppler fetal activ~y mon~or (Actograph MT-320, To~u Corp.). The fetal startle response (characterized by sudden gross body movements and flexion-extension of all extrem~ies lasting 5-10 seconds after VAST) was observed ultrasonographcally in 20 addi­tional patients (10 breech and 10 vertex). Chi square analysis re­vealed virtually identical FHR responses in both groups. The increase in the number of FM after VAST compared to the pre-stimulation baseline was not different between groups. The fetal startle response was uniforn,ly observed in both groups. VAST over the fetal breech elicijs an identical short term fetal response compared to stimulation over the fetal vertex with a potentially less intense sound exposure. Until more is known about the long term effects of VAST on fetal hearing, stimulation over the breech may be preferable.

January 1992 Am J Obstet Gynecol

518 FETAL HEART RATE ACCELERATIONS, FETAL MOVEMENT AND FETAL BEHAVIOR PATTERNS IN TWIN GESTATIONS. M.W, Gallagher,' T.R.B Johnson, Dept. Gyn/Ob, The Johns Hopkins Univ. Sch. of Med., Balto., MD. 21205

Previous studies have shown that twins, when monitored simultaneously, show a remarkably high incidenca of synchronous fetal heart rata accelerations (58%), prompting inquiry into the nature of the intrauterine interaction of twins. The present study is a retrospective examination of 20 fetal monitor strips from five sets of twins with simultaneous fetal heart rate and fetal activity recorded using a doppler fetal movement detector (Toitu MT -320-Fetal Actocardiograph). The strips were analyzed for coincidence of fetal heart rate accelerations and/or fetal movement episodes. Forty-eight percent of fetal heart rate accelerations were found to be simultaneous. Fifty-seven percent of movement epochs were considered simultaneous. The strips were then analyzed using concepts of fetal behavioral patterns based on descriptions of behavioral states by Prechtl and Nijhuis. We found that twins exhibited coincident bebavioral patterns (basically sleep/awake state) 88% of the time. Twin-twin interactions are more consistently related than suspected when observation is limited to heart rate alone and the coincidence of and role of fetal behavioral states must be considered when twin interactions and behavior are studied.

519 AMNIOTIC FLUID VOLUME ESTIMATION IN THE POSTDATES PREGNANCY: A COMPARISON OF TECHNIQUES. RL Fischer, M McDonnelr, KW Bianculli" RL Perry, TO Scholl', ML Hediger. Department of OB/GYN, UMDNI-RWI Medical School at Camden, Cooper HospitallUniversityMedica1 Center, Camden, NJ.

A number of techniques for amniotic fluid volume (AFV) estimation have been proposed, including the largest vertical pocket (LVP) and amniotic fluid index (AFI). Oligohydramni08has been variously defined as LVP< I or 2 cm, or AFI < 5 cm or 2.5th percentile. Purpose: To determine the AFV technique that was most predictive of abnormal perinatal outcome in 137 postdates pregnancies. Gestational dating was based on an early ultrasound ~26wks) which either con­firmed or established the BOD, or a late ultrasound that was consistent with or greater than the menstrual age. With the ultrasound transducer in a longitudinal plane, the largest amniotic fluid pocket in each quadrant was measured in both vertical and transverse dimensions. The last AFV prior to delivery was correlated with perinatal outcome. Outcome was considered abnormal for: I) operative delivery for non-reassuring FHR tracing, 2) meconium below the cords, 3) 5 minute Apgar <7, 4) umbilical artery pH <7.10 or venOU8 pH <7.15, 5) admission to NICU, or 6) BW < 10%. A receiver operating characteristic (ROC) curve was employed to determine the optimal L VP and AFJ. Results: The mean L VP was significantly lower in the abnormal outcome group compared to the normal group (3.4 ± 2.0 V8 4.2 ± 1.4 cm, p = .04), whereas no significant difference was noted using the AFI (8.7 ± 5.5 vs 9.7 ± 4.3 cm, p = .24).

Normal Outcome Abnormal Outcome AFV Test (N = 103) (N =34) I! LVP < I cm 0 (0%) 3 (8.8%) .01 LVP <2 cm 3 (2.9%) 8 (23.5%) .0006 ROC LVP <2.5 cm 8 (7.8%) 12 (35.3%) .0003 AFI <5 cm 12 (11.7%) 8 (23.5%) .10 AFI <2.5% 21 (20.4%) II (32.4%) .15 We conclude from our study of postdates pregnancies that: I) an LVP <2.5 cm is the most useful AFV indicator of subsequent abnormal perinatal outcome, with a sensitivity of 35.3% and a specificity of 92.2%, and 2) the AFI has little diagnostic value in this population.