Volu me 164 Number I , Part 2

462 ACUTE PARTIAL lITERINE BLOOD FLOW OCa.USION INCREASES PROSTAGLANDIN F METABOUTE BUT NOT lITERINE CONTRAcnONS. GJ Valenzuela, M Norburg", and CA Ducsay". Div Perinatal Biology and Dept Obstetrics and Gynecol, Lorna Linda Univ, California.

Premature labor is associated with a 30% incidence of small for gestational age, and the partial reduction of uterine blood flow produces an increase in the uterine contractions (UC) in primates. To test the hypothesis that acute hypoxia could be one of the causative agent for premature labor, 6 ewes at 120 days of gestation were chronically catheterized. Five days after surgery, graded occlusion of the common uterine artery were initiatated via a snare, at 30 min interval (control, 30%, 60% and complete occlusion). Uterine blood flow and the intraamniotic fluid pressure were recorded continuously (total time=120 min) . Amniotic fluid samples were collected and analyzed for prostaglandin F-2alpha metabolites (PGFM) . Mean PGFM (pg/ml) ± SEM for control, 30%, 60%, and complete occlusion were 679 ± 60, 791 ± 88 (p<0.02 from control), and later increased to 827 ± 113 at 90 min, and 823 ± 111 at 120 min, respectively. There were no change in UC throughout the observation period (p>O.I). In conclusion, intrauterine hypoxia produced an increase in amniotic fluid PGFM. It is not unreasonable to speculate that under chronic conditions, hypoxia could trigger premature labor via stimulation of prostaglandins production.

463 UTERINE MYOMAS: A CAUSE FOR PRETERM DELIVERY?

J Ludmjr MD F Teplick MSNx, P Samuels MD, C Lindenbaum MD, AW Cohen MD. University of Pennsylvania Medical Center,

Philadelphia, PA.

In the absence of submucosal myomas and the presence of a normal uterine cavity, the role of intramural or subserosal myomas in causing preterm labor is controversial. Although myomas can enlarge during gestation, the possible mechanisms responsible for preterm labor are unknown. We describe 25 patients known to have a normal uterine cavity and large uterine myomas (>5cm), without other risk factors for preterm labor. These patients were managed by the same group of physicians, under the same protocol of frequent visits and cervical assessment. All patients had education regarding signs and symptoms of preterm labor, and were monitored by ambulatory tocodynamometry begining at 20-22 weeks gestation. Increased uterine activity with advancing gestation (>4 contractions/hr) was shown in 15 of 25 patients (60%). 01 these patients, 10 (66%) developed preterm labor requiring intravenous tocolysis. 01 the 25 patients, 9 (36%) delivered a preterm infant. Nine of the 10 patients (90%) requiring tocolysis delivered prematurely, whereas none of the remaining 15 patients without increase uterine activity, underwent a preterm birth (p<O.OOI). Conclusions: 1) Patients with large uterine myomas, regardless of a normal uterine cavity, are at high risk for preterm labor. 2) Once the need for intravenous tocolysis develops, there is a high risk of preterm delivery. 3) The role of myomectomy and/or medical therapy for this group of patients needs to be defined.

SPO Abstracts 373

464 AMBULATORY TOCODYNAMOMETRY IN DES-EXPOSED PREGNANT WOMEN

J Ludmjr MD. F Teplick MSNx, P Samuels MD, C Linderbaum MD, AW Cohen MD

University of Pennsyvlania School of Medicine, Philadelphia, PA

The DES exposed pregnant patient is at risk for adverse pregancy outcome and preterm delivery. We deSCribe our experience with 35 patients exposed to DES in utero, in which home uterine monitoring was started between 20-22 weeks gestation. All patients were followed weekly by the same group of physicians under the same management protocol. 16 patients (46%) (Group A) had DES exposure as the only risk factor for preterm delivery. These patients had normal cervical structure and no history of loss. The remaining 19 patients (Group B) had a cerclage placed for either a history of pregnancy loss, cervical hypoplasia or cervical change detected dUring gestation. Overall, 37% of all patients experienced preterm labor as detected by the home uterine monitor. 14% had preterm delivery «37 weeks) associated with preterm rupture membranes. When analyzed by group, 7 of 16 patients in group A (44%) experienced preterm labor with 4 of 16 (25%) delivering preterm. Six patients in Group B (32%) had preterm labor with five patients delivering before term (26%). We conclude that DES exposed pregnant patients are at risk for preterm labor regardless of cervical structure or pregnancy history. Intense obstetric surveillance is justified in this group of patients.

465 EARLY IDENTIFICATION OF RISK FOR PRETERM LABOR AND DEUVERY: THE INFORMATION CONTENT OF THE MORPHOMETRY OF A POSITIVE MAMMARY STIMULATION TEST (MST) A.D. Eden. M.p., A.J. Sokol, M.D., Y. Sorokin, M.D., H. Cook", RNC, BSN , G. Sheeranx

, RNC and L. Chikx, Ph.D.. Wayne

State University, Detroit, Michigan Based upon the supposition that the MST reveals the "state"

of the myometrium vis-a-vis the sensitivity to oxytocin endogenously released by nipple stimulation and a simple definition of MST positivity (any uterine contractility on testing between 24 and 32 weeks), we have previously reported that MST results significantly Improve the predictability of preterm labor and delivery, beyond that from clinical risk factors alone (Am J Obstet Gyneco1, in press). To determine whether additional information could be obtained from the MST to improve the prediction of preterm labor and delivery, we analyzed the morphometry of positive MST tracings from 51 patients. Of the 51, 26 (51%) entered preterm labor and 17 (33%) delivered prematurely. Discriminant analyses relating clinical risk factors and measures of uterine irritability and contractility to preterm labor and delivery revealed that the presence of uterine contractions prior to, during and following nipple stimulation was predictive of preterm labor (chi-square = 4.02, p<0.05) and delivery (explained variance 28.3%). These findings indicate that the morphometry of the MST gives information beyond that of high-risk factors and enables the clinician to identify an ultra-high-risk group of patients destined to experience preterm labor and deliver preterm. Patients at highest risk fOl' preterm labor and delivery are characterized by a profile comprised of the presence of clinical risk factors, a positive MST and evidence of labor-llke rhythmic uterine contractions (relative risk 5.0, explained variance 41 %). If these findings can be validated in additional samples, the MST may find broad use in prematurity prevention programs.