Does an amniotic fluid index of </=5 cm necessitate delivery in high-risk pregnancies? A case-control study

OBJECTIVE

This study was undertaken to determine whether women with high-risk pregnancies and an amniotic fluid index of </=5 cm require labor induction to prevent adverse perinatal outcomes.

STUDY DESIGN

All women at high risk at >/=34 weeks' gestation with an amniotic fluid index of </=5 cm were admitted to the hospital for labor induction. Each woman was compared with the next patient at high risk seen with an amniotic fluid index of >5 cm and the same pregnancy complication. Case patients were also matched with control subjects for maternal race, age, parity, and gestational age.

RESULTS

Prospectively, 79 women at high risk with an amniotic fluid index of </=5 cm were compared with 79 control subjects. There were no statistically significant differences between the 2 groups in the risks of thick meconium (P =.29), variable decelerations (moderate P =.27, severe P =.37), amnioinfusion (P =.37), cesarean delivery for fetal distress (P =.4), and umbilical artery pH <7.10 (P =.29).

CONCLUSION

High-risk pregnancies with an amniotic fluid index of </=5 cm appear to carry intrapartum complication rates similar to those of similar high-risk pregnancies with an amniotic fluid index of >5.

Early risk assessment of severe preeclampsia: admission battery of symptoms and laboratory tests to predict likelihood of subsequent significant maternal morbidity

OBJECTIVE

This study was undertaken to investigate the utility of an admission battery of findings and laboratory data in the discrimination of patients with severe preeclampsia with or without HELLP (hemolysis, elevated liver enzyme levels, and low platelet count) syndrome at high risk for development of significant maternal morbidity.

STUDY DESIGN

The clinical and laboratory findings at hospital admission for 970 patients with severe preeclampsia with or without HELLP syndrome were studied retrospectively to develop parameters associated with low, moderate, and high risks for the subsequent development of significant maternal morbidity involving the hematologic and coagulation, cardiopulmonary, and hepatorenal systems.

RESULTS

Nausea and vomiting and epigastric pain are independent risk factors for complicated severe preeclampsia. Results of a panel of tests with values including lactate dehydrogenase level >1400 IU/L, aspartate aminotransferase level >150 IU/L, alanine aminotransferase level >100 IU/L, uric acid level >7.8 mg/dL, serum creatinine level >1.0 mg/dL, and 4+ urinary protein by dipstick can be used to discriminate the patient at high risk for significant maternal morbidity. Concentrations of lactate dehydrogenase, aspartate aminotransferase, and uric acid above these cut points have the strongest predictive value and are risk additive with worsening thrombocytopenia.

CONCLUSION

The presence of nausea and vomiting, epigastric pain, or both in association with admission laboratory values that are in excess of the cutoffs for lactate dehydrogenase, aspartate aminotransferase, and uric acid concentrations or for all 6 tests is predictive of high risk of morbidity for the patient with severe preeclampsia. These factors are independent of and additive with the rising maternal risk associated with decreasing platelet count.

Detection of growth-restricted fetuses in preeclampsia: a case-control study

OBJECTIVE

To determine the diagnostic accuracy of detecting growth-restricted fetuses in women with and without preeclampsia.

METHODS

Over 2 years, parturients with reliable gestational ages, preeclampsia, and sonographic estimates of birth weights were matched (1:1) for gestational age with women without preeclampsia. Paired and unpaired t tests were used; P < .05 was significant. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

RESULTS

Two hundred eighty-seven preeclamptic women were identified and matched. In each group, mean (+/- standard deviation [SD]) gestational age was 34.9 +/- 4.2 weeks, and 166 (57.8%) infants were born preterm. Fetal growth restriction (FGR) was significantly more common among women with preeclampsia (14.9%) than among controls (5.6%; OR 2.98, 95% CI 1.64, 5.44). The percentage of sonographic estimates within 10% of actual birth weight (57.5% versus 53.6%) was similar in the two groups (OR 1.16; 95% CI 0.84,1.62). Compared with normal growth, the mean (+/- SD) standardized absolute error was significantly higher among those with FGR regardless of group (preeclampsia 109 +/- 100 versus 158 +/- 152 g/kg; P = .009; control 117 +/- 103 versus 233 +/- 206 g/kg; P < .001). Fetal growth restriction was detected more commonly among preeclamptic women than among controls (11.6% versus 0%; OR 4.74 95% CI 0.25, 90.31). The sensitivity and positive predictive value of FGR detection were 10% and 50%, respectively, among women with preeclampsia and 0% each among controls.

CONCLUSION

Although FGR was detected more frequently in fetuses of women with preeclampsia than in those of controls, the ability to predict it with sonography remained poor.

Risk factors for secondary arrest of labor among women >41 weeks' gestation with an unfavorable cervix undergoing membrane sweeping for cervical ripening

OBJECTIVE

To identify the risk factor(s) for secondary arrest of labor among women with an unfavorable cervix at > 41 weeks' gestation.

METHODS

Prospectively all gravid women with a Bishop score of < or = 4 and no contraindication to a vaginal delivery were candidates for this study. Univariate analysis followed by logistic regression modeling were used to identify variables with a significant association.

RESULTS

Over a 9-month period, 115 women entered into the study. In univariate analysis, variables with a significant association with cesarean delivery: (1) non-Caucasian race (P = 0.007), Bishop score < 7 at hospitalization; P = 0.001, and reason for admission (P = 0.017). Logistic regression analysis yielded OR 4.7 (1.6, 15) non-Caucasian race and 9.5 (3.2, 30.8) Bishop < 7 on admission.

CONCLUSION

Pregnancies > 41 weeks with an unfavorable cervix, non-Caucasian race and a failure to achieve a Bishop score of > or = 7 prior to hospitalization were significant risk factors for abdominal delivery.

Dexamethasone-facilitated postponement of delivery of an extremely preterm pregnancy complicated by the syndrome of hemolysis, elevated liver enzymes, and low platelets

OBJECTIVE

Patients with severe preeclampsia and the syndrome of hemolysis, elevated liver enzymes, and low platelets (HELLP syndrome) are at increased risk for perinatal and maternal morbidity, especially in very preterm gestations. When this condition affects a pregnancy on the cusp of viability, a therapeutic intervention to prolong gestation without undue risk to the mother or fetus could be beneficial.

METHOD

A single case report and review of the literature.

RESULT

We report a patient with HELLP syndrome in whom antenatal administration of high-dose dexamethasone helped achieve disease stabilization and delivery postponement for 9 days of a very preterm fetus estimated to weight less than 600 g. Both mother and infant did well postpartum.

CONCLUSION

Administration of antenatal high-dose dexamethasone can be used in carefully selected preterm patients with HELLP syndrome to delay delivery while in utero fetal maturation is accelerated and the maternal condition is optimized. This can be beneficial in carefully selected pregnancies without apparent adverse maternal or perinatal impact.

Preeclampsia-associated hepatic hemorrhage and rupture: mode of management related to maternal and perinatal outcome

This article is a critical review of the obstetric literature concerning preeclampsia-associated hepatic hemorrhage to develop guidelines conducive to optimal maternal and perinatal outcomes. An English literature search was performed for reports of hepatic hemorrhage or hepatic rupture in pregnancy during 1960 to 1997. Data were analyzed by Statmost packages using ANOVA, Chi-square, and Fisher's exact tests. One hundred forty-one patients with hepatic rupture/hemorrhage were reported. The three most common presenting findings were epigastric pain, hypertension, and shock. With rare exception, patients had evidence of preeclampsia. Diagnosis was elusive and most frequently accomplished at laparotomy. When utilized, ultrasound and computed tomography (CT) were helpful diagnostic modalities. Maternal survival was highest in the arterial embolization treatment group. Maternal and perinatal survival improved considerably during the study interval. Route of delivery did not seem to impact survival rates. It was concluded that the application of ultrasound and CT for diagnosis and the use of hepatic artery embolization for treatment of hepatic hemorrhage/rupture seem to be beneficial management options for this rare event.

Membrane sweeping versus dinoprostone vaginal insert in the management of pregnancies beyond 41 weeks with an unfavorable cervix

OBJECTIVE

To determine the best method of cervical ripening to prevent postdate inductions in women with an unfavorable cervix at 41 weeks' gestation.

STUDY DESIGN

Women presenting at 41 weeks' gestation with a Bishop score of < or = 4 received daily dinoprostone (Cervidil) vaginal inserts (group I) or daily membrane sweeping (group II).

RESULTS

One-hundred and eighty-two women were prospectively randomized with 91 women in each arm. The women in group II, membrane sweeping, had Bishop scores significantly greater on admission for delivery (p < 0.001), had less time elapsed from admission to delivery (p = 0.018), and had fewer labor inductions at 42 weeks (p = 0.04) than the women in group I, the dinoprostone group. In addition, a greater number of women in group II were admitted in spontaneous labor (p = 0.006) than in group I. Total antenatal costs for the membrane sweeping group was $15,120 versus $59,540 for the dinoprostone group.

CONCLUSION

Daily membrane sweeping was more effective than dinoprostone administration with fewer postdate inductions at one-fourth the cost.

Amniotic fluid index in normal pregnancy: a longitudinal study

OBJECTIVE

This longitudinal study was undertaken to characterize the change in the amniotic fluid volume in normal pregnancy.

METHODS

Prospectively, patients with uncomplicated gestations underwent serial amniotic fluid index by a single sonographer.

RESULTS

Fifty-six patients underwent a total of 378 determinations of amniotic fluid volume (6.8 +/- 2.5 examinations per patient). The variation in mean amniotic fluid index between 24 and 40(+6) weeks was not significantly different (p = 0.381). Among the 42 patients who delivered at term there was no significant decrease in the amniotic fluid index between their first and last measurement (p = 0.86). However, in the 14 patients who delivered after 41 weeks, there was a significant decrease in the index over time (p = 0.04).

CONCLUSION

The longitudinal study on amniotic fluid volume in normal pregnancy reveals that amniotic fluid index does not change significantly with gestational age.

Intrapartum amniotic fluid index: a poor predictor of abnormal fetal size

OBJECTIVE

Using receiver-operating characteristic (ROC) curves, we tried to determine the diagnostic threshold of amniotic fluid index (AFI) that will identify abnormal fetal size (birth weights under 2500 g or at least 4000 g) at 37 weeks or beyond.

METHODS

We analyzed prospectively over 2 years all parturients with intact membranes and known AFI in early labor. Patients with the following conditions were excluded: pregestational or gestational diabetes, known anomalies, and preterm labor. Two ROC curves were constructed, and the areas (+/- standard error of the mean [SE]) under the curves were calculated. P < .05 was considered significant.

RESULTS

Of the 1038 subjects meeting study criteria, 3.6% and 11.5% gave birth to infants who were small for gestational age (SGA) or macrosomic, respectively. Overall, 28.7% had oligohydramnios (AFI at most 5.0 cm) and 3.6% had hydramnios (AFI at least 24.0 cm). Small for gestational age was more common in patients with AFI at most 5.0 cm (6.4%) than in those with adequate fluid (AFI 5.1-23.9; 2.5%), or hydramnios (2.7%; P = .012). Macrosomic newborns were less likely to be born to women with oligohydramnios (7.7%) than to those with adequate amniotic fluid (13.1%) or hydramnios (13.5%). Areas under ROC curves are not significantly different from the area under the nondiagnostic line, indicating that AFI (0-34 cm) cannot differentiate between newborns under 2500 g and at or over 2500 g or under 4000 and at or more 4000 g.

CONCLUSION

Intraparterium AFI appears to be a poor screening test to identify risk for delivery of SGA or macrosomic fetus.

Placental implantation at 18 weeks and migration throughout pregnancy

BACKGROUND

We wanted to find the most frequent site of placental implantation at 18 weeks' gestation and placental migration during gestation.

METHODS

Placental location was identified in 2,526 singleton pregnancies at 18 weeks' gestation and characterized into nine groups. Placental migration in 1,336 of these pregnancies was assessed by serial ultrasonography.

RESULTS

At 18 weeks' gestation, posterior, high placental implantation was more common (45.1%) than anterior, high implantation (42.1%). Relocation of posterior, high placentas farther fundally (16.9%) was three times more likely than farther fundal migration of anterior, high placentas (4%).

CONCLUSIONS

Posterior fundal placental implantation is more common at 18 weeks' gestation than anterior implantation. Posteriorly implanted placentas are more likely than anterior placentas to migrate farther fundally during gestation. The greater relocation of posterior placentas farther fundally suggests a greater growth of posterior versus anterior uterine wall smooth muscle.

Can we decrease postdatism in women with an unfavorable cervix and a negative fetal fibronectin test result at term by serial membrane sweeping?

OBJECTIVE

Our purpose was to determine whether the risk for postdatism can be reduced by serial membrane sweeping in women with an unfavorable cervix at 39 weeks' gestation and a negative fetal fibronectin test result.

STUDY DESIGN

Women with uncomplicated pregnancies, who were candidates for a vaginal delivery with an unfavorable cervix at 39 weeks' gestation and a negative fetal fibronectin test result were asked to participate in this investigation. Patients were chosen at random and assigned to a group for membrane sweeping every 3 days or to a control group who received gentle examinations every 3 days.

RESULTS

Sixty-five women were selected at random for serial membrane sweeping (n = 33) or for the control group (n = 32). Although gestational age and Bishop score at study entry were similar, the gestational age on admission for delivery was earlier in the membrane sweeping group (39.9 +/- 0.3) versus the control group (41.5 +/- 0.6, P < .0001). The Bishop score on admission to labor and delivery was greater (8.8 +/- 2.1) in the membrane sweeping group than in the control group (6.2 +/- 2.7, P < .0001). The number of women admitted for labor inductions at 42 weeks' gestation was 18 of 32 (56%) in the control group versus none (0 of 24) in the membrane-sweeping group (P < .0001).

CONCLUSIONS

Women with an unfavorable cervix at 39 weeks' gestation and a negative fetal fibronectin test result are at risk for not being delivered by 41 completed weeks and thus may require postdates induction or antenatal testing. Serial membrane sweeping significantly reduces the risk of postdatism and induction of labor.

Effect of amniotic fluid volume on neonatal outcome in diamniotic twin pregnancies

PROBLEM

We assessed neonatal outcome of normal diamniotic twin pregnancies with known amniotic fluid (AF) volume.

METHOD

The AF volume was empirically determined in 39 diamniotic twin gestations. The neonates were stratified by AF volume and evaluated for clinical outcome, gestational age, lecithin-sphingomyelin (L/S) ratio, and birth weight.

RESULTS

Neonatal complications did not significantly differ among infants delivered from pregnancies with low (155 to 404 mL), moderate (405 to 807 mL), or high (808 to 5,430 mL) volumes of AF. Relatively constant volumes of AF were maintained throughout the 27 to 38 week range of gestational age, with no apparent correlation between AF volume and gestational age. Variations in the L/S ratio and newborn birth weights were also independent of AF volume. Gestational age was the only significant determinant of the frequency of neonatal complications.

CONCLUSION

Amniotic fluid volume does not greatly affect neonatal outcome in normal diamniotic twin pregnancies.

Absence of seasonal variation on the frequency of HELLP syndrome

BACKGROUND

We wanted to determine the relationship between weather/seasonal conditions and the incidence/severity of HELLP syndrome.

METHODS

We retrospectively reviewed medical records of all patients with class 1 (platelet nadir < or = 50,000/microL), class 2 (platelet nadir > 50,000/microL but < or = 100,000/microL), and class 3 (platelet nadir > 100,000/microL but < or = 150,000/microL) HELLP syndrome, who had been treated at the University of Mississippi Medical Center between January 1, 1980, and December 31, 1992.

RESULTS

No seasonal differences were observed in the incidence or severity of pregnancies complicated by HELLP syndrome.

CONCLUSION

HELLP syndrome appears to occur throughout the year without any seasonal variation.

Amnioinfusion-induced malpresentation

Amnioinfusion is a valuable and common intrapartum procedure for the relief of cord compression and to dilute thick meconium. Like most procedures, it is not without risk and we report a case of malpresentation following amnioinfusion. Intrapartum fetal demise occurred after malpresentation during amnioinfusion resulting in a change of fetal presentation from vertex to unrecognized shoulder presentation. Further study is needed regarding changes in volume of amniotic fluid and saline as well as intrauterine manipulation and the effect on fetal presentation. Careful attention must be paid to infused volumes during amnioinfusion.

Hematological complications of Gaucher's disease in pregnancy

A case is presented of a 31-year-old Filipino female, gravida 5 para 2, at 38 weeks plus 5 days gestation, with known type I Gaucher's disease who underwent repeat cesarean delivery. After cesarean delivery, the patient developed disseminated intravascular coagulation and required transfusion of eight 6-packs of platelets, 6 units of fresh frozen plasma, two 10-packs of cryoprecipitate, and 6 units of packed red blood cells. Pregnancy is generally well tolerated in patients with type I Gaucher's disease, an autosomal recessive lysosomal storage disorder in which lipid deposits accumulate in the liver, spleen, and bone marrow. Hemorrhagic problems secondary to severe thrombocytopenia may develop postpartum in pregnancies complicated by Gaucher's disease, requiring significant support with blood and blood products.

Management of pregnancies beyond forty-one weeks' gestation with an unfavorable cervix

OBJECTIVE

Our purpose was to determine the optimal management of pregnancies beyond 41 weeks' gestation with a cervix unfavorable for induction.

STUDY DESIGN

All uncomplicated pregnancies that reached 41 weeks' gestation with a Bishop score of < or = 4 were randomly assigned to one of three groups: (1) daily cervical examinations, (2) daily membrane stripping, or (3) daily placement of prostaglandin gel until 42 weeks.

RESULTS

In 105 pregnancies the Bishop score on admission to labor and delivery was significantly greater in the groups receiving prostaglandin or stripping of the membranes versus the control group, whereas the converse was time of gestational age at delivery (p = 0.0001). Fewer patients required induction in the two treatment groups (20%, 17%) versus the control (69%) patients (p < 0.0001).

CONCLUSIONS

Daily membrane stripping or daily placement of prostaglandin gel is successful in reducing the number of inductions at 42 weeks for postdatism.

Home blood pressure monitoring for pregnant patients with hypertension

OBJECTIVE

To determine whether automated measurement of blood pressure and pulse in a home setting can be easily accomplished by pregnant women with chronic hypertension.

STUDY DESIGN

In this prospective investigation, seven women with chronic hypertension complicating pregnancy recorded their blood pressure at home twice a day. These data were offloaded once daily into a computer at a remote site, and a computerized printout of these data was received by the physician.

RESULTS

The patients participated in the study for 12.2 +/- 5.8 weeks (range 4 to 18 weeks) and were between 23 and 42 weeks' gestation. Average mean arterial pressure in the home was 102 +/- 10 mm Hg, and average pulse was 81 +/- 11 beats per minute. In the clinic, the values were 112 +/- 13 mm Hg and 90 +/- 30 beats per minute (p < 0.05). Each patient was easily taught how to use the machine.

CONCLUSIONS

The home blood pressure monitoring device was easy to use and correlated well with values recorded by health professionals for this limited number of subjects. It was particularly helpful to patients (n = 5) who lived long distances (more than 60 miles) from the clinic and to women who needed adjustments of antihypertensive medication.

Do multiple measurements employing different ultrasonic techniques improve the accuracy of amniotic fluid volume assessment?

This investigation was undertaken to determine if the accuracy of the ultrasound assessment of abnormal amniotic fluid volume (oligohydramnios or polyhydramnios) is improved by employing multiple sonographic amniotic fluid measurements. Four ultrasound techniques consisting of the subjective assessment (ultrasonic visualization without measurement), largest vertical pocket, amniotic fluid index and 2-diameter pocket technique were performed followed by amniocentesis and dye-dilution confirmation of amniotic fluid volume in 66 singleton pregnancies. The ultrasound accuracy to detect abnormal amniotic fluid volume ranged from 61% with the largest vertical pocket to 70% with the 2-diameter pocket procedure used separately. Receiver operator characteristic curves demonstrated that combining the 4 ultrasonic measurements did not improve the accuracy of identifying amniotic fluid volumes.

Bishop score: a poor diagnostic test to predict failed induction versus vaginal delivery

BACKGROUND

We evaluated the accuracy of the Bishop score in predicting the likelihood of successful labor induction (entry into active phase) in nulliparous and multiparous women.

METHODS

During an index year, all patients having induction of labor and a preinduction Bishop score were included in a standard protocol for cervical ripening and use of oxytocin. Receiver-operating characteristic (ROC) curves were constructed for Bishop scores (0 to 11) to predict abdominal delivery for failed induction (final cervical dilation <4 cm) versus vaginal delivery.

RESULTS

Parturients who had vaginal delivery (n = 253) and those in whom attempted induction failed (n = 38) did not differ significantly with respect to maternal demographics, length of gestation, Bishop score and its distribution, and infant birth weight. The area under the ROC curve did not differ significantly from the area under the nondiagnostic line.

CONCLUSION

The Bishop score appears to be a poor predictor of the outcome of labor induction.

Comparison of intra-amniotic (15S)-15-methyl-PGF2 alpha and intravaginal prostaglandin E2 for second-trimester uterine evacuation

OBJECTIVE

To compare the efficacy, safety, and side effects of intra-amniotic (15S)-15-methyl prostaglandin F2 alpha (15-M-PGF2 alpha) and intravaginal prostaglandin E2 (PGE2) for midtrimester uterine evacuation.

STUDY DESIGN

Ninety-three patients underwent therapeutic midtrimester pregnancy termination by the use of laminaria placement and intra-amniotic injection of 15-M-PGF2 alpha. A matched control group underwent uterine evacuation by laminaria placement and insertion of PGE2 intravaginal suppositories. The main outcomes studied were time to delivery, side effects, and complications.

RESULTS

The 15-M-PGF2 alpha group had a shorter time to delivery (12.3 +/- 6.4 hours) compared with the PGE2 group (16.2 +/- 6.6 hours, p < 0.0001). The evacuation rate over time was significantly greater in the 15-M-PGF2 alpha group (p = 0.001). The PGE2 group had a significantly higher incidence of side effects.

CONCLUSIONS

The use of intra-amniotic 15-M-PGF2 alpha for therapeutic second-trimester pregnancy termination is safe and is associated with a more rapid evacuation of the uterus and fewer side effects than intravaginal PGF2 suppositories.

Limitations of clinical and sonographic estimates of birth weight: experience with 1034 parturients

OBJECTIVE

To compare the accuracy of clinical and sonographic estimates of fetal weight made throughout the third trimester of pregnancy.

METHODS

Patients in early labor had fetal weight estimated by two approaches: 1) clinical evaluation and palpation followed by 2) sonographic mensuration of fetal biparietal diameter, abdominal circumference, and femur length applied to Hadlock's formula. The accuracy of these two methods of estimating fetal weight was compared using Student t test, Wilcoxon test, and chi2 tests. P < .05 was considered significant. Prediction limits (50th, 90th, and 95th percentiles) were calculated for both techniques by obtaining the range of actual weights associated for a particular estimated fetal weight (EFW).

RESULTS

We enrolled 1034 parturients whose clinical EFWs yielded significantly higher mean (+/- standard deviation) simple error (48.2 +/- 411 g) and standardized absolute error (130 +/- 122 g/kg) than were obtained by use of sonographic formulas for EFW (-6.6 +/- 381 g and 104 +/- 89 g/kg, respectively). When the population was partitioned by gestational age, we found that sonographic EFW was more accurate than clinical EFW in preterm (n = 373) but not in term (n = 460) or post-term (n = 201) pregnancies. Prediction limits indicate that for a given EFW, for example, 800 g, the 90% ranges of actual weight based on clinical and sonographic EFW are 566-1829 g and 469-1667 g, respectively.

CONCLUSION

The apparent superiority of sonographic EFW over clinical EFW applies principally to preterm pregnancies. The prediction limitation calculation suggests that either method, for any particular estimate between 500 and 4500 g, has limited value in the estimation of actual birth weight, because this outcome is highly variable and frequently lies outside of the useful bandwidth (+/- 10%) for prospective management.

Mathematical models to correlate amniotic fluid index and amniotic fluid volume

PURPOSE

To describe a predictable relationship that relates amniotic fluid index (AFI) to amniotic fluid volume (AFV) and improve the accuracy of AFI to detect true oligohydramnios.

METHODS

Data from 42 parturients (group I) who underwent measurements of amniotic fluid sonographically (amniotic fluid index) as well as by dye-dilution technique was used to relate AFI to AFV. Subsequently, 22 consecutive women (group II) were used to test the accuracy of the equation to predict true oligohydramnios.

RESULTS

In group II, 11 of 22 patients had true oligohydramnios and the sensitivity, specificity, positive and negative predictive values of AFI < or = 5.0 to detect a confirmed AFV < 500 mL were 0%, 91%, 0%, and 48%, respectively. These values of AFI, when used in conjunction with the equation, improved to 73%, 55%, 62%, 67%, respectively. With AFI and the equation, significantly more patients in group II with true oligohydramnios (8 of 11) could be detected than with using AFI alone (0 of 11; p = 0.002).

CONCLUSION

AFI is poor predictor of true oligohydramnios. Using the mathematical model, the detection rate of oligohydramnios is significantly improved.

The accuracy of the summated amniotic fluid index in evaluating amniotic fluid volume in twin pregnancies

OBJECTIVE

Our purpose was to determine the accuracy of the summated amniotic fluid index designed to estimate the total amniotic fluid volume in twin pregnancies.

STUDY DESIGN

The summated amniotic fluid index was measured in 62 normal diamniotic twin pregnancies by adding the deepest vertical pockets in the four quadrants. Actual amniotic fluid volume was then determined in all 124 amniotic sacs by amniocentesis and a dye-dilution technique. For data analysis, amniotic fluid volumes were classified by percentile with use of previously reported norms.

RESULTS

There were significant differences in the percentile distribution of amniotic fluid volume as estimated by the summated amniotic fluid index and the actual volume as determined by dye dilution (p < 0.001). The summated amniotic fluid index has a sensitivity of only 13% in predicting amniotic sac volume.

CONCLUSION

The summated amniotic fluid index is a poor predictor of intertwin differences in amniotic fluid volume and cannot identify twin pairs at risk for oligohydramnios and hydramnios.

Amniotic fluid volume in normal singleton pregnancies

OBJECTIVE

To evaluate the amniotic fluid (AF) volume in normal singleton pregnancies from 15 to 40 weeks.

METHODS

This prospective study evaluated the AF volume in singleton pregnancies undergoing amniocentesis for genetic assessment of fetal karyotype, preterm labor, or fetal lung maturity. Amniotic fluid volume was determined using a dye dilution technique. To assess the relationship between AF volume and estimated gestational age, a nonlinear regression model was applied.

RESULTS

One hundred forty-four normal singleton pregnancies had AF volume evaluated. There was wide variability in the measured AF volumes with a significant (P < .01) increase in AF volume as a function of gestational age. Growth curve modeling estimated that AF volume continued to increase until 40 weeks' gestation. Analyses of the observed AF volume indicated that AF volume nearly doubled after 30 weeks' gestation.

CONCLUSION

In contrast to other reports indicating that maximal AF volume in singleton gestations is expected early in the third trimester, we observed the attainment of maximal AF volume near term.

Ultrasonographic assessment of amniotic fluid does not reflect actual amniotic fluid volume

OBJECTIVE

Our objective was to compare the ability of two methods of amniotic fluid assessment (two-diameter amniotic fluid pocket versus the amniotic fluid index) to predict oligohydramnios (actual amniotic fluid volume < 500 ml) or polyhydramnios (actual amniotic fluid volume > 1500 ml).

STUDY DESIGN

The amniotic fluid index and the two-diameter amniotic fluid pocket were assessed before amniocentesis and determination of amniotic fluid volume with the dye (aminohippurate sodium)-dilution technique. To assess the detection of either oligohydramnios or polyhydramnios, the areas under the receiver-operator characteristic curves (+/-SE) were estimated by the point-to-point trapezoidal method of integration. Prediction limits were calculated by regression analysis of amniotic fluid index or two-diameter amniotic fluid pocket versus actual amniotic fluid volume and determination of 95th percentile ranges for amniotic fluid volume.

RESULTS

We studied 144 patients with a mean (+/-SD) gestational age of 31.7 +/- 5.5 weeks; mean (+/-SD) amniotic fluid index and two-diameter amniotic fluid pocket were 12.6 +/- 6.1 cm and 21.2 +/- 18.4 cm2, respectively. Mean (+/-SD) actual amniotic fluid volume was 722 +/- 735 ml (range 101 to 4318 ml). The areas under the four receiver-operator characteristic curves were not significantly different from the nondiagnostic line (p < 0.05). Regression slopes (r values) for amniotic fluid index and two-diameter amniotic fluid pocket versus actual amniotic fluid volume were 0.34 and 0.23, respectively. Calculation of the prediction limit for 95% confidence that oligohydramnios is absent requires that the amniotic fluid index be 30 cm and the two-dimension amniotic fluid pocket be 90 cm2, both thresholds of which are currently considered to represent clinical polyhdramnios.

CONCLUSIONS

Both amniotic fluid index and two-dimension amniotic fluid pocket appear to be inaccurate predictors of actual oligohydramnios or polyhydramnios when compared with dye-dilution calculations of actual amniotic fluid volume.