Isolated oligohydramnios in the term pregnancy: Is it a clinical entity?

S144

SPO Abstracts

Januax y 1997 A m J Obstet Gynecol

495

THE ASSOCIATION OF PLACENTA PREVIA WITH HISTORY OF CESAREAN DELIVERY AND ABORTION: A META-ANALYSIS. CVAnanth, ~ JC Smu{ian, A M Vintzileos. Department of OB/GYN, UMDNJ-Robert Wood Johnson Medical School/St. Peter's Medical Center, New Brunswick, New Jersey. OBJECTIVE: To determine the incidence of placenta previa based on available epidemiologic evidence, and to quantify the risk of previa based on the presence and number of cesarean deliveries as well as a history of spontaneous and induced abortions. STUDY DESIGN: We reviewed studies on placenta previa published between 1950 and 1995 based on a comprehensive literature search using MEDLINE and by identifying studies cited in the references of published reports. Data on the incidence of previa, and its associations with previous cesarean delivery and abortions were abstracted. Studies were grouped based on design (case-control versus cohort studies). Statistical methods employed for the meta-analysis included the fixed-effects logistic regression model, while potential sources of heterogeneity among studies was evaluated by fitting random-effects models. RESULTS: The tabulation of 37 studies identified a total of 3.7 million pregnant women of whom 13,992 patients were diagnosed with placenta previa. The reported incidence of placenta previa ranged between 0.28% to 1.0%, or approximately 1 in 200 deliveries. No discernible trends over time in the incidence of previa were apparent. Women with at least one prior cesarean delivery were 2.6 (95% confidence interval (CI) 2.3-3.0) times at greater risk of developing placenta previa in a subsequent pregnancy. The results varied by study design, with case-control studies showing a stronger relative risk (RR-3.8, 95% CI 2.3-6.4) than cohort studies (RR 2.4, 95% CI 2.I-2.8). Four studies encompassing 170,640 pregnant women showed a dose-response pattern for the risk of previa based on the number of prior cesarean deliveries. Relative risks were 4.5 (95% C] 3.6-5.5) for one, 7.4 (95% CI 7.1-7.7) for two, 6.5 (95% CI 3.6-11.6) for three, and 44.9 (95% CI 13.5-149.5) for four or more prior cesarean deliveries. Women with a prior history of spontaneous or induced abortion had a risk of previa of 1.6 (95% CI 1.0-2.6) and 1.7 (95% CI 1.0-2.9), respectively. Substantial heterogeneity in the results of the rneta-analysis was noted among studies. CONCLUSION: There is a strong association between having a previous cesarean delivery, spontaneous, or induced abortion and the subsequent development of placenta previa. The risk increases with number of prior cesarean deliveries. Pregnant women with a history of cesarean delivery or abortion must be regarded as high risk for placenta previa and must be monitored carefully. This study provides yet another reason fbr reducing the primary cesarean delivery rate, and for advocating vaginal birth for women with prior cesarean delivery.

497

MANAGEMENT OF THE POSTDATE PREGNANCY A T TWO CANADIAN TERTIARY CENTERS: IMPACT OF THE CANADIAN MULTICENTER POSTDATE TRIAL. M. Helewa, C Harman ~, C Mustard ~, J. MarteIL Dept. Ob/Gyn, Univ. of Manitoba, Winnipeg, MB. OBJECTIVE: Evaluate changes in management of the postdate pregnancy at two tertiary centers in Manitoba, following the outcome of the Canadian muhicenter RCT, recommending induction of labor at 41+ weeks to reduce cesarean section rates (CS) especially for fetal distress. STUDY DESIGN: Retrospective, gestation age specific, analysis of pregnancies beyond 40 week in distribution of deliveries, induction rates, overall CS rates, and CS rates for induction vs. spontaneous labor before and after the release of the trial results (April 1994). RESULTS: Among 7172 deliveries before and 4287 deliveries after 1994, the % of deliveries at 41 weeks increased from 17.5% to 19.5% (p<.001) but were reduced at 42 weeks from 5% to 1.9% (p<.001). Induction rates increased from 22% (n 1622) to 27% (n=1162), with a peak rise at 41+ weeks from 34% (1057/3098) to 43% (766/1779)(p<.001), mostly for postdates. Induction rates for pregnancies undelivered at 42+ weeks were unchanged (67% vs. 68%). There was no change in overall CS rates (12.56% vs. 12.50%), nor in CS rates for women in spontaneous labor (11.8% vs. 12.4%) after 40+ weeks between the two time periods. A reduction in CS rates from 15.7% to 13.5% was observed for patients subjected to induction of labor at 41+ weeks (166/1057 vs. 104/766) and in CS rates for all deliveries at or beyond 41 weeks (14.6% to 13.9%) but was not statistically significant(p-.2). Indications for CS especially for fetal distress remained unchanged. CONCLUSIONS: The two centers complied with the conclusion of the RCT. Distribution of deliveries has shifted one week earlier with many women induced at 41+ weeks. There was no significant reduction in CS rates for patients induced at 41 + weeks, nor in the overall CS rates for women after 40 weeks or 41+ weeks gestation.

496

PLACENTA PREVIA: TRANSFUSION FREQUENCY AND THE UTILITY OF A U T O L O G O U S BLOOD DONATION. Anne C Regenstein, Elliott K Main. Dept. Ob/Gyn, Kaiser Foundation Hospital and California Pacific Medical Center, San Francisco, CA. OBJECTIVE: There is limited data on current transfilsion practices in cases of placenta previa. Therefore, we examined the incidence and need for transfusion among women with placenta previa and explored the utility of autologous blood donation (AD). STUDY DESIGN: A database and chart review of 188 women with a delivery diagnosis of previa at two large tertiary care centers from 1/1/926 / 3 0 / 9 6 was performed. Criteria for AD were a 3rd trimester hematucrit (hct) >32% and diagnosis of previa at least 3 weeks pre1500 cc, hct <20%, or hypotension &/or tachycardia with bleeding or anemia. RESULTS: 36 (19%) women received transfusions, 7 (4%) had a hysterectomy and 5 (3%) had a coagulopathy. Half of the transfusions occurred during scheduled deliveries including those transfused >- 5 units. 24% of those with a prior cesarean received a transfusion (p=ns). 6 women received AD blood: 3 transfusions were not indicated and 2 wmnen required additional units of non-AD blood. 6 women received designated donor (DD) blood: 2 transfusions were not indicated and 3 women required blood from non-DD. Of the 31 (17%) indicated transfusions, 19 wmnen received < 3 units. Of these 19, 10 were candidates for AD, 4 were not and 5 could not be assessed.

498

ISOLATED OLIGOHYDRAMNIOS IN THE TERM PREGNANCY: IS IT A CLINICAL ENTITY?. D.L. Conwa'~~, W.B. Adkins ~, B. Schroeder~, O. Langev: Dept. of Ob/Gyn, UTHSCSA OBJECTIVE: To test the hypothesis that when isolated oligohydramnios is found at term in the othel~vise normal pregnancy, perinatal outcome is worse than pregnancies with normal amniotic fluid volume. METHODS: All obstetric patients at term (37 to 41-6/7 weeks gestation) who unde1~-ent induction of labor for the sole indication of oligolwdramnits during the study period were compared to a control group consisting of spontaneously laboring patients with normal anmiotic fluid index (AFI), matched for gestational age and parity. Oligohydramnios was defined as AFI <5.0 cm. Exclusion criteria were: non-cephalic presentation, nruhiple gestation, ultrasound estimated fetal weight <10th percentile for gestational age, hypertensive complications, diabetes mellitus and ruptured membranes. Outcome variables examined included: meconimn-stained amniotic fluid (MSAF), route of delivelw, indication for cesarean section (C/S), acidosis (arterial cord pH<7.15), low 5-minute Apgar (<7), admission to NICU, and cost of hospitalization for mother and infant. RESULTS: A total of 366 patients met inclusion criteria (oligo groupn - 1 8 3 ; control group-n=183). Maternal characteristics and demographic data were similar between the two groups.

Transfusions by # of units and delivery gestational age #PRBC

all n=36

indicated n= 31

I

I

weeks

all n= 36

>-36 >32<36 <32

21 9 6

m

1 2 3-4 >--5

7 17 4 8

(19%) (47%) (12%) (22%)

4 5 4 8

(13%) (48%) (13%) (26%)

CONCLUSIONS: In this large study of women with placenta previa there was a high rate of transfusion (19%); however, at most only 6% of women were potential AD candidates, delivered after 34 weeks and needed and received < 3 units PRBC.

I AFI < 5.0 AFI (cm _+ S.E.) BW* (g + S.E.) MSAF (%) All Mod/Thick Acidosis (%) Low Apgar (%) NICU (%) C / S (%)

3.1 _+ 0.1 3398 -+ 34 24.9 13.7 10.4 1.1 16.6 15.8

nlAFI 7.6 + 0.2 3427 -+ 35 23.6 12.6 7.1 0.5 11.5 6.6

P value~OR (95% CO <0.001 NS 1.1 (0.7-1.8) 1.1 (0.6-2.1) 1.5 (0.7-3.2) 2.0 (0.2-22.4) 1.5 (0.8-2.8) 2.7 (1.3-5.4)

*Birthweight There was no difference between the two groups in rate of C / S for fetal distress [33.3% vs. 23.1%, OR 1.7 (0.4-7.6)]. The study group also had significantly higher cost of maternal hospitalization ($2977 vs. $2510, p<0.01). CONCLUSION: The data in our study" suggest that perinatal outcome in patients with isolated oligohydramnios in an otherwise normal term pregnancy is comparable to that of the general population (normal AFI). Thus, clinical intervention (induction of labor) for isolated oligohydramnios will result only in increased C / S rate and cost of care for the mother.