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Volume 166 Number 1, Part 2

INTRAPARTUM FETAL HEART RATE ASSESSMENT: MON ITORI NG BY AUSCULTATION, J.e. Morrison, B.F. Chez,X !.D. Davis,X J.R. Allbert,X R.W. Martin, W.E. Roberts, J.N. Martin, Dept. Ob/Gyn, Univ. Mississippi Med. Ctr., Jackson, MS

Obj ect i ve: To determi ne if i ntermi ttent auscu ltat ion of fetal heart rate (FHR) using strict frequency of evaluation and documentation criteria is feasible under clinical conditions in a busy labor and delivery suite in a tertiary center. Pat i ent Popul at ion: Du ri ng a 3-month period, 862 consecut1ve women 1n labor with live fetuses between 24 and 43 weeks' gestation were avai I abl e for intrapartum auscultation of FHR (case series study des i gn). Ma in Outcome Measu red: Whether or not ausculation could be 1n1t1ated and maintained for evaluation of FHR during the intrapartum period with a frequency requirement of auscultation and documentation of 15 mi nutes in the fi rst stage of I abor and 5 mi nutes during the second stage. Results: In 420 patients, this modal i ty was not begun duetoTnabi I i ty of the nurses to meet 1:1 staffing requirements. In 19 patients, auscu I tat i on was not performed due to obes i ty (12) or pat i ent refusa I (7) whi lei n the rema i ni ng 423 patients it was begun. Auscultation was initiated during a contraction and extended for 30 seconds after the uterine activity ceased. It was repeated every 15 minutes in the fi rst stage and 5 mi nutes in the second stage of labor. Of the 423 asses sed by auscu I tat ion, 392 were unable to comp I ete moni tori og due to the frequency requ i rement (n=212) or the recording criteria (n=163). Of the 31 patients where ausculation was used successfully, labor was < 6 hours in 22 patients. In 9 patients who successfully completed ausculation, there was a 1:1 nurse ratio during the entIre labor. Conclusion: Auscultation offered duri ng the intrapartum penod usi ng stri ngent evaluation and recording criteria Is not feasible under normal labor and delivery suite conditions unless a 1:1 nursing ratio Is always available. This degree of staffing Is rarely possible for the majority of obstetrIc areas in the United States duri ng the entire labor.

EFFECfS OF MAGNESIUM SULI'A'IT ON FETAL HEART RATE MONITORING IN TIlE PRE'IT'RM FETUS. JW Wright!.2 DD Wright,'X LE Ridgway,' DL Covington,lX JR !lobittl lArea Health Edue. Clr, Wilmington, NC; 2Univ. of Texas Health Science etr at San Antonio

Previous studies have reported that magnesium sulfate (MgS04) alters important characteristics of fetal heart rate monitoring. However, the rcsulL~ of these studies arc inconsistent and most used preeclamptic patients ncar term. Because pre term labor is associated with other high risk conditions, the effects of M£SO~ tocolysis on fetal heart rate monitoring are clinically important. We sought to evaluate these e!Tects using 1) objective criteria with decreased variability defined as oscillation band width <6 bpm, normal variability as 6.:25 bpm, and increased variability as >25 bpm; and 2) subjective evaluation with variability graded as absent, decreased, normal or increased. Agreement of '2 of 3 blinded examiners was used to define the categories. We prospectively collected fetal heart rate tracings for 30 minutes before and after MgS04 loading in 48 prelerm labor patients. We compared pre- and post-therapy rcsulL<.; using McNemar's test for categorical data and a paired Hcst for baseline fetal heart ratc. No monitor tracings were read as having absent or increased variability.

I Results Pre (n=4&) Post (n=48)

Baseline filR 1408 137.3 .001

NST Reactive 26 21 NS

Objective Variabili!y .13 Band width 6-25 48 44 Band width <6 0

Subjective Variabili!y .006 ~ormal 46 J6 Decreased 12

SubjectIve evalualIon demonstrated a greater hkehhood of decreased variability after MgSO. loading_ However, lo~s of variability was not shown by objective measurcment. We conclude that MgSO, tocolysis may be associated with subjectively decreased variability.

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spa Abstracts 317

FETAL PULSE OXIMETRY DURING LABOUR J (,ardosi', C Schram', D Damianou', EM Symonds'

Perinatal Research & Moniloring Unit, Oueens Medical Centre, N"ttingham, England

Pulse oximetry, the non-invasivc measurement of arterial oxygcn saturation, has hccomc a principle form of monitoring in scvcral specialities. In perinatolof,'Y, its application has been hampered by poor access to the fetus. We have developed a fetal oximeter probe which is held on the scalp by means of a double Copeland clip. The probe can be applied from 2 em cervical dilatalion and a continuous, on-line trend of oxygen saluration can be recorded straight onto the cardiotocograph paper. Preliminary results (105 labours) showed that saturation values on the felal scalp present a slable baseline during normal labour (70 - 9(1%, median H2'!"). An unslable trend and a fall to below ()() % saturation was ohserved during the development of fetal acidosis. Our in vitro and animal studies have confirmed that fetal Hb dissociation curves arc sensitive to the Bohr shift and give lower oxygen saturation levels during acidosis. Artifacts may arise due to non-arterial pulsations - c_g_ from caput - and we have shown that this error can he excluded hy signal processing which analyses both electronic (ECG) and optic (plethysmo­graphic) signals and rejects non-synchronised readings. Incomplete apposition of the prohe results in false-low readings; we have quantified Ihis error and shown Ihal Ihe AC and DC components of the oximeler signal arc affected differentially, thus affecting the calculations by the oximeter. Our probe failed in the presence of thick fetal hair, and a new probe is being developed which avoids this problem by apposing sensors to felal skin away from hairy scalp. Pulse oximetry holds enormous promise for improving felal surveillance during labour bUI successful adaptation requires attention to the particular difficulties and errors that may arise from this new application.

MECONIUM: MARKER FOR HIGH-RISK PREGNANCIES. M. Berkus, A. Samueloff,' E. Xenakls.' N. Field.' L Ridgway, O. Langer. Dept. OB/GYN, The Univ. Texas Health Science Center, San Antonio, TX.

Traditionally, meconium (MEC) portends impending or ongoing fetal compromise, but recently this association has been questioned. Controversy exists regarding the relationship of MEC with abnormal fetal heart tracings, Apgar scores, pH and outcome. In this study, we sought to characterize the outcome of the patient with MEC stained amniotic fluid. Over 2,000 con~e(utive deliveries were analyzed by a team of perinatologists, including scoring of the cardiotocograms (after Krebs). The incidence of term (.>2500 g) babies with moderate or thick MEC was 16.7%. Mothers with (horioamnionitis and gestational diabetes had an increased incidence of MEC (35.6% and 21.4%, respectively; p" 03). In contrast, no significant increase in MEC was found in SGA (14.3%), hypertensive (14.4%) or prolonged pregnancies (194%) when compared to the non MEC group. Infants with MEC were found at significantly increased risk for:

1st stage FHR abnormal 2nd state FHR abnormal APGAR 1" ,.7 APGAR 5" ,,7 pH"- 7.2 Sepsis Oxygen support NICU admission

MEC(%) 20.9 49.B 154

2.5 26.9

4.1 92

13.5

NOMEC(%) 13.5 20.2

5.8 0.5

136 1.1 30 2.9

RR(95%CI) 15 (1.2 20) 2.5 (1931) 27(1741) 5.0 (16156) 20(1427) 36(1681) 3 1 (12 BO) 4.6(1911.3)

The-stud-y also-revealedihat MEC infants-'were-':;:;ore like!yth-a-n non MEC to: 1) be delivered by emergency CIS (154% vs 9.8%, p<. .03); 2) experience adverse neonatal outcome (8.3% vs 3.9%, p,,-0.2), as defined by NICU stay, respiratory distress, or abnormal neurological sequelae; and 3) have significantly more adverse outcome when associated with bradycardia or decreased variability (p<, 03), but not with tachycardia or lack of dccelerations Our data suggests that, even with modern OB care, a pregnancy with meconium is at incr eased jeopardy and should be considered high risk.