Antenatal testing among 1001 patients at high risk: the role of ultrasonographic estimate of amniotic fluid volume

Isolated oligohydramnios and long-term neurological morbidity of the offspring

This study aimed to assess the association between maternal-isolated oligohydramnios (IO) and offspring long-term neurological complications. A population-based retrospective cohort study was conducted, including all births at a single tertiary medical center in Israel between the years 1991 and 2014. Multiple pregnancies and potential pregnancy complications associated with oligohydramnios were excluded. The computerized obstetrical database was linked with the computerized dataset of all pediatric hospitalizations of the same medical center. Evaluation of cumulative neurological-associated hospitalizations rate over time was compared using a Kaplan-Meier survival curve. The Weibull survival parametric model was conducted to assess the neurological-associated hospitalization risk in the presence of IO, while accounting for potential confounders. A total of 190,259 pregnancies were included in the study, of which 4063 (2.13%) pregnancies were complicated with IO. Total neurological-related hospitalizations were significantly more common in the IO group (3.7% in the IO group and 3.0% in the comparison group, p = 0.005). Pervasive developmental disorder, movement disorders, developmental disorders, and degenerative and demyelization disorders were all specific neurological diagnoses significantly more common in the exposed group. The survival curve demonstrated a significantly higher cumulative hospitalization rate in the exposed group (log-rank p = 0.001). Using a multivariate model adjusting for gestational age, maternal age, and labor induction, an independent association between IO and long-term neurological morbidity of the offspring was observed (adjusted hazard ratio 1.203; 95% CI 1.02-1.42). In summary, a significant association was found between pregnancies complicated by IO and long-term neurological morbidity of the offspring.

Perinatal outcomes with isolated oligohydramnios at term pregnancy

AIMS

To compare the outcomes of term gestations with oligohydramnios in the absence of other underlying disorders and term gestations with normal amniotic fluid.

METHODS

A retrospective analysis of obstetric outcomes in 27,708 term pregnancies. We compared three groups: labor induced because of oligohydramnios, spontaneous onset of labor with normal amniotic fluid, and labor induced because of late term pregnancy with normal amniotic fluid. We excluded pregnancies with maternal or fetal diseases or disorders potentially related with amniotic fluid alterations. The main outcome measures were mode of delivery, neonatal birth weight, umbilical artery blood pH, Apgar scores and neonatal discharge status.

RESULTS

Compared to spontaneous labor, induction of labor because of oligohydramnios was associated with a higher risk of cesarean delivery and small size of the fetus for gestational age (SGA). Compared to induction because of late term pregnancy there were no significant differences in neonatal, although neonates had a higher risk of being SGA.

CONCLUSION

The only perinatal outcome for which the risk was higher in term pregnancies with isolated oligohydramnios was SGA. The systematic induction of labor in these pregnancies should be questioned.

Antenatal fetal surveillance "Assessment of the AFV"

The evaluation of amniotic fluid volume (AFV) is an established part of the antenatal surveillance of pregnancies at risk for an adverse pregnancy outcome. The two most commonly used ultrasound techniques to estimate AFV are the amniotic fluid index (AFI) and the single deepest pocket (SDP). Four studies have defined normal AFVs, and although their normal volumes have similarities, there are also differences primarily due to the statistical methodology used in each study. Dye-determined AFV correlates with ultrasound estimates for normal fluid volumes but correlates poorly for oligohydramnios and polyhydramnios. The addition of color Doppler in estimating AFV leads to the overdiagnosis of oligohydramnios. Neither the AFI nor the SDP is superior in identifying oligohydramnios, but the SDP is a better measurement choice as the use of AFI increases the diagnosis rate of oligohydramnios and labor inductions without an improvement in pregnancy outcomes.

Diagnosis and Treatment of Hypertensive Pregnancy Disorders. Guideline of DGGG (S1-Level, AWMF Registry No. 015/018, December 2013)

Purpose: Official guideline published and coordinated by the German Society of Gynecology and Obstetrics (DGGG). Hypertensive pregnancy disorders contribute significantly to perinatal as well as maternal morbidity and mortality worldwide. Also in Germany these diseases are a major course for hospitalization during pregnancy, iatrogenic preterm birth and long-term cardiovascular morbidity. Methods: This S1-guideline is the work of an interdisciplinary group of experts from a range of different professions who were commissioned by DGGG to carry out a systematic literature search of positioning injuries. Members of the participating scientific societies develop a consensus in an informal procedure. Afterwards the directorate of the scientific society approves the consensus. Recommendations: This guideline summarizes the state-of-art for classification, risk stratification, diagnostic, treatment of hypertensive pregnancy disorders.

Fetal imaging: executive summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging workshop

Given that practice variation exists in the frequency and performance of ultrasound and magnetic resonance imaging (MRI) in pregnancy, the Eunice Kennedy Shriver National Institute of Child Health and Human Development hosted a workshop to address indications for ultrasound and MRI in pregnancy, to discuss when and how often these studies should be performed, to consider recommendations for optimizing yield and cost effectiveness, and to identify research opportunities. This article is the executive summary of the workshop.

Fetal imaging: Executive summary of a Joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging Workshop

Given that practice variation exists in the frequency and performance of ultrasound and magnetic resonance imaging in pregnancy, the Eunice Kennedy Shriver National Institute of Child Health and Human Development hosted a workshop to address indications for ultrasound and magnetic resonance imaging in pregnancy, to discuss when and how often these studies should be performed, to consider recommendations for optimizing yield and cost-effectiveness and to identify research opportunities. This article is the executive summary of the workshop.

Fetal imaging: executive summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging Workshop

Given that practice variation exists in the frequency and performance of ultrasound and magnetic resonance imaging (MRI) in pregnancy, the Eunice Kennedy Shriver National Institute of Child Health and Human Development hosted a workshop to address indications for ultrasound and MRI in pregnancy, to discuss when and how often these studies should be performed, to consider recommendations for optimizing yield and cost effectiveness, and to identify research opportunities. This article is the executive summary of the workshop.

A nationwide survey of risk factors for stillbirth in Taiwan, 2001-2004

OBJECTIVE

The purpose of this study was to evaluate the nationwide stillbirth rate and explore the potential risk factors associated with stillbirths.

PATIENTS AND METHODS

Data from vital registrations during the time period from January 1, 2001 through to December 31, 2004 in Taiwan were used. Stillbirth was defined as fetal death with more than 20 completed weeks' gestational age (GA) or with birth weight more than 500 g if the GA was not known.

RESULTS

There were a total of 8481 stillbirths identified nationwide between January 1, 2001 and December 31, 2004. The stillbirth rate was nine per 1000 total births in the study period, and the proportionate decline was nearly 48.8% in the most recent decade. There was a significant increase in average maternal age during this period. Advanced maternal age and teenage pregnancy were independent significant risk factors for stillbirths even after accounting for the effects of medical conditions that were more likely to occur among these particular age groups. Those fetuses that had been exposed to cord prolapse, maternal cervical incompetence and oligohydramnios/polyhydramnios were especially vulnerable. By contrast, women who had foreign nationality, fetal ultrasound surveys, fetal heart beat monitoring and hastened parturition were less likely to have stillbirth.

CONCLUSION

The stillbirth rate in Taiwan has remained high despite advancements in medical care. Prenatal evaluation of high risk women may decrease the adverse fetal outcomes.

[Management of post-term pregnancies: the role for AFI, biophysical score and doppler]

OBJECTIVE

To evaluate the role of ultrasound and doppler assessment in the management of prolonged pregnancies and to state its modalities.

METHOD

Medline, PubMed, embase and the Cochrane library were searched using terms prolonged pregnancy, post date pregnancy amniotic fluid, ultrasound assessment, doppler, biophysical profile.

RESULTS

Single deepest vertical pool measurement is the method of choice of the assessment of amniotic fluid. Indeed, when this method was used, significantly fewer case of oligohydramnios were diagnosed and fewer women had inductions of labor. However, this method is not superior to the amniotic fluid index in the prevention of poor perinatal outcomes. There is a significant difference in the incidence of fetal distress, meconium stained fluid and caesarean section for fetal distress when the amniotic fluid is reduced as compared with normal amniotic fluid. However, sensibility and predictive positive value of oligohydramnios to predict poor perinatal outcomes is moderate. Similary, in most studies, diagnosis of an abnormal uterine, umbilical, aortic or cerebral blood flow doppler was associated with a weak prediction of a poor perinatal outcome. Therefore, we do not recommend its use in management of prolonged pregnancy. There were significantly more diagnosis of oligoamnios and more abnormal antenatal monitoring results in the modified biophysical profile group as compared with the group managed with only single deepest pool but no differences in cord blood gases, neonatal outcome, or in outcomes related to labour and delivery were noted between the two groups. Therefore, biophysical profile including AFI offers no advantage in detecting adverse outcomes and may cause more interventions.

CONCLUSION

Close monitoring of fetal condition including assessment of amniotic fluid by single deepest pool twice a week from 41 weeks of gestation is recommended in the management of prolonged pregnancy. Induction of labor could be considered when oligohydramnios is diagnosed by single deepest pool less than 2 cm.

Amniotic fluid and the clinical relevance of the sonographically estimated amniotic fluid volume: oligohydramnios

The amniotic fluid volume (AFV) is regulated by several systems, including the in-tramembranous pathway, fetal production (fetal urine and lung fluid) and uptake (fetal swallowing), and the balance of fluid movement via osmotic gradients. The normal AFV across gestation has not been clearly defined; consequently, abnormal volumes are also poorly defined. Actual AFVs can be measured by dye dilution techniques and directly measured at cesarean delivery; however, these techniques are time-consuming, are invasive, and require laboratory support, and direct measurement can only be done at cesarean delivery. As a result of these limitations, the AFV is estimated by the amniotic fluid index (AFI), the single deepest pocket, and subjective assessment of the AFV. Unfortunately, sonographic estimates of the AFV correlate poorly with dye-determined or directly measured amniotic fluid. The recent use of color Doppler sonography has not improved the diagnostic accuracy of sonographic estimates of the AFV but instead has led to overdiagnosis of oligohydramnios. The relationship between the fixed cutoffs of an AFI of 5 cm or less and a single deepest pocket of 2 cm or less for identifying adverse pregnancy outcomes is uncertain. The use of the single deepest pocket compared to the AFI to identify oligohydramnios in at-risk pregnancies seems to be a better choice because the use of the AFI leads to an increase in the diagnosis of oligohydramnios, resulting in more labor inductions and cesarean deliveries without any improvement in peripartum outcomes.

Oligohydramnios, small for gestational age and pregnancy outcomes: an analysis using precise measures

BACKGROUND/AIM

Marginal or decreased amniotic fluid volume by ultrasound estimate and fetal growth restriction have been shown to be significantly associated with perinatal mortality. The association of fetal growth restriction and precisely measured amniotic fluid volume is unknown. The purpose of this study was to determine if adverse pregnancy outcomes are more likely in pregnancies complicated by small-for-gestational-age (SGA) neonates and dye-determined oligohydramnios.

METHODS

Admissions to neonatal intensive care unit (NICU) and other pregnancy outcomes were analyzed in parturients with known amniotic fluid volume, calculated by the dye-dilution technique. The pregnancy outcomes of those with oligohydramnios and SGA were compared with pregnancies complicated by just one of these two conditions and pregnancies with normal fluid and birth weight.

RESULTS

Of 202 patients, oligohydramnios was present in 26% (53), SGA in 15% (30) and both conditions in (5%) (11). Logistic regression, controlling for gestational age, demonstrated that the combination of oligohydramnios and SGA, compared to normal growth and fluid strongly predicted NICU admission (OR 11.1; 95% CI 2.1-59.2) but not other complications. (OR 4.8; 95% CI 0.3-62.9).

CONCLUSIONS

SGA with oligohydramnios significantly increases the likelihood of a NICU admission, but not other morbidity.

Borderline or marginal amniotic fluid index and peripartum outcomes: a review of the literature

The predictive accuracy of a borderline amniotic fluid index (AFI) for an adverse pregnancy outcome is uncertain. Pregnancy outcomes of a borderline versus normal AFI suggest an increased risk of meconium-stained fluid, intrauterine growth restriction, cesarean delivery for a nonreassuring fetal heart rate, low Apgar scores, and neonatal intensive care unit admission with borderline fluid. These results are inconclusive because of study design variations, the absence of receiver-operating characteristic curves, our inability to calculate likelihood ratios, and a lack of randomized trials. There is currently insufficient evidence to recommend additional antenatal testing delivery based on a borderline AFI. Sonography could be considered for evaluating fetal growth until a definitive association or lack of an association between a borderline AFI and intrauterine growth restriction/small size for gestational age can be determined.

Peripartum outcomes of high-risk pregnancies complicated by oligo- and polyhydramnios: a prospective longitudinal study

AIM

To determine pregnancy outcomes in high-risk non-anomalous singleton pregnancies with oligo- and polyhydramnios.

METHODS

In high-risk pregnancies undergoing antenatal testing, the last amniotic fluid index (AFI) prior to delivery in pregnancies with polyhydramnios (>97.5th percentile) and oligohydramnios (<2.5th percentile) was correlated with pregnancy outcomes.

RESULTS

There were 2597 pregnancies with a normal AFI (2.5th-97.5th percentile), 73 with hydramnios (AFI > 97.5th percentile) and 72 with oligohydramnios (<2.5th percentile). Polyhydramnios and oligohydramnios adversely influenced different pregnancy outcomes. Pregnancies with polyhydramnios versus normal AFI were more likely to have: an abnormal tracing influencing delivery (29% vs 17%, odds ratio [OR] = 2.03, 95% confidence interval [CI] 1.19-3.45, P = 0.009), cesarean delivery performed due to fetal labor intolerance (21% vs 7%, OR = 3.89, 95%CI 2.10-7.18, P < 0.001), increased birthweight (P = 0.016), Apgar score <7 at 5 min (8% versus 1%, OR = 6.41, 95%CI 1.12-16.22, P = 0.001) and newborn intensive care unit admission (10% versus 5%, OR = 2.24, 95%CI 1.12-4.49, P = 0.023). Pregnancies with oligohydramnios versus normal AFI had a greater risk of labor induction (18% vs 9%, OR = 3.18, 95%CI 1.62-6.25, P = 0.001), intrauterine growth restriction (25% vs 9%, OR = 3.4, 95%CI 1.94-5.97, P < 0.001) and preterm delivery (29% vs 17%, OR = 1.97, 95%CI 1.17-3.31, P = 0.010).

CONCLUSIONS

Fetal heart rates influencing delivery, cesarean deliveries for fetal labor intolerance, low 5-min Apgar scores, increased neonatal birthweight, and newborn intensive care unit admissions were more common with polyhydramnios. The fetuses of pregnancies complicated by oligohydramnios had a greater risk of labor induction, intrauterine growth restriction and preterm delivery.

Isolated oligohydramnios in term pregnancy as an indication for induction of labor

OBJECTIVE

To evaluate the outcome of active induction of labor for isolated oligohydramnios in low-risk term gestation.

METHODS

This retrospective study analyzed the obstetric and perinatal outcome of 412 singleton term pregnancies with cephalic presentation and no maternal risk factors or fetal abnormalities. Two groups were compared: 206 deliveries after induced labor for isolated oligohydramnios, and 206 deliveries matched for gestational age following spontaneous labor with normal amniotic fluid index.

RESULTS

The overall rate of cesarean deliveries and cesarean deliveries for nonreassuring fetal status, and operative vaginal delivery rates and those for nonreassuring fetal status were higher in the oligohydramnios group than in the control group. There were no differences between groups in neonatal outcome or perinatal morbidity or mortality.

CONCLUSION

Active induction of labor in term low risk gestations with isolated oligohydramnios translated into higher labor induction, operative vaginal delivery and cesarean section rates. This led to increased maternal risk and an increase in costs with no differences in neonatal outcome.

Amniotic fluid index versus single deepest vertical pocket: a meta-analysis of randomized controlled trials

OBJECTIVE

To compare the use of the amniotic fluid index with the single deepest vertical pocket measurement, during antepartum fetal surveillance, in preventing adverse pregnancy outcome.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (January 2008), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, Issue 2), MEDLINE (1966 to May 2008), and the metaRegister of Controlled Trials (May 2008). We handsearched the citation lists of relevant publications, review articles, and included studies.

SELECTION CRITERIA

Randomized controlled trials involving women with a singleton pregnancy, whether at low or high risk, undergoing ultrasound measurement of amniotic fluid volume as part of antepartum assessment of fetal well-being that compared the amniotic fluid index and the single deepest vertical pocket measurement.

DATA COLLECTION AND ANALYSIS

Both authors independently assessed eligibility and quality, and extracted the data.

RESULTS

Four trials (3125 women) met the inclusion criteria. When the amniotic fluid index was used, significantly more cases of oligohydramnios were diagnosed (risk ratio (RR) 2.33, 95% CI 1.67-3.24), and more women had inductions of labor (RR 2.10, 95% CI 1.60-2.76) and cesarean delivery for fetal distress (RR 1.45, 95% CI 1.07-1.97). There is no evidence that one method is superior to the other in the prevention of poor peripartum outcomes, including: admission to a neonatal intensive care unit; an umbilical artery pH of less than 7.1; the presence of meconium; an Apgar score of less than 7 at 5 minutes; or cesarean delivery.

CONCLUSION

Single deepest vertical pocket measurement is the method of choice for the assessment of amniotic fluid volume.

Amniotic fluid index versus single deepest vertical pocket as a screening test for preventing adverse pregnancy outcome

BACKGROUND

Amniotic fluid volume is an important parameter in the assessment of fetal well-being. Oligohydramnios occurs in many high-risk conditions and is associated with poor perinatal outcomes. Many caregivers practice planned delivery by induction of labor or caesarean section after diagnosis of decreased amniotic fluid volume at term. There is no clear consensus on the best method to assess amniotic fluid adequacy.

OBJECTIVES

To compare the use of the amniotic fluid index with the single deepest vertical pocket measurement as a screening tool for decreased amniotic fluid volume in preventing adverse pregnancy outcome.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (January 2008), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 2), MEDLINE (1966 to May 2007) and the metaRegister of Controlled Trials (May 2007). We handsearched the citation lists of relevant publications, review articles, and included studies.

SELECTION CRITERIA

Randomised controlled trials involving women with a singleton pregnancy, whether at low or high risk, undergoing ultrasound measurement of amniotic fluid volume as part of antepartum assessment of fetal well-being that compared the amniotic fluid index and the single deepest vertical pocket measurement.

DATA COLLECTION AND ANALYSIS

Both authors independently assessed eligibility and quality, and extracted the data.

MAIN RESULTS

Four trials (3125 women) met the inclusion criteria. There is no evidence that one method is superior to the other in the prevention of poor peripartum outcomes, including: admission to a neonatal intensive care unit; an umbilical artery pH of less than 7.1; the presence of meconium; an Apgar score of less than 7 at five minutes; or caesarean delivery. When the amniotic fluid index was used, significantly more cases of oligohydramnios were diagnosed (risk ratio (RR, random) 2.33, 95% CI 1.67 to 3.24), and more women had inductions of labor (RR (fixed) 2.10, 95% CI 1.60 to 2.76) and caesarean delivery for fetal distress (RR (fixed) 1.45, 95% CI 1.07 to 1.97).

AUTHORS' CONCLUSIONS

The single deepest vertical pocket measurement in the assessment of amniotic fluid volume during fetal surveillance seems a better choice since the use of the amniotic fluid index increases the rate of diagnosis of oligohydramnios and the rate of induction of labor without improvement in peripartum outcomes. A systematic review of the diagnostic accuracy of both methods in detecting decreased amniotic fluid volume is required.

[Current recommendations for the treatment of preeclampsia]

Low-dose aspirin, but not vitamin C and vitamin E, has small to moderate benefits when used for the prevention of preeclampsia. There is however little to suggest that the course of manifest preeclampsia can be substantially affected by drug treatment. Antihypertensive therapy increases the risk of fetal growth restriction and is only indicated in severe hypertension to reduce the risk of maternal cerebral hemorrhage. Magnesium sulfate is the drug of choice for the prevention and treatment of eclampsia. Volume expansion as well as the use of steroids in preeclamptic patients without HELLP syndrome have failed to show any improvement. Delivery as the only definitive treatment is always beneficial for the mother whereas expectant management is in favor of a premature fetus. Decision-making largely depends on gestational age and severity of the disease.

Reevaluation of the relationship between amniotic fluid volume and perinatal outcome

OBJECTIVE

Ultrasound estimation of amniotic fluid volume (AFI) is a critical component of antenatal surveillance. Alterations in AFI have classically been considered an indication of fetal compromise, but recent studies have called this into question. The present study was undertaken to reevaluate the relationship between AFI and perinatal outcome.

STUDY DESIGN

The perinatal data base of the authors' institution was queried for all patients in a 6-year period who had AFI evaluated. Two groups, 1 high-risk and 1 low-risk, were evaluated to determine the relationship between AFI and gestational age. An additional high-risk group that had AFI determined within 48 hours of delivery was also used to correlate AFI with intrapartum and perinatal outcomes. Statistical analysis was performed using linear regression analysis to evaluate the correlation between AFI and gestational age or birth weight. Additional correlations were done using analysis of variance, chi-square, Fisher exact test, or Student t test. Interaction between variables was analyses using logistic regression analysis.

RESULTS

Fourteen thousand seven hundred forty-seven AFI determinations in 4337 high-risk patients, and 1153 AFI determinations in 1153 low-risk patients were evaluated. There were no clinically significant correlations between AFI and gestational age. In the second high-risk group of 454 patients there was a significant correlation between polyhydramnios and large-for-gestational age infants, congenital anomalies, and an increase in cesarean section for delivery. There was an increased risk of nonreassuring fetal heart rate patterns during labor for the oligohydramnios patient, but only in preterm patients. There was no strong relationship between AFI and neonatal complications or length of stay in the neonatal intensive care unit. Logistic regression confirmed that AFI was not significantly correlated with perinatal outcome.

CONCLUSION

The present study suggests that AFI is a weaker predictor of perinatal outcome than has been classically suggested. Although the AFI identification of polyhydramnios was helpful in identifying LGA fetuses and fetuses at risk for congenital abnormalities, oligohydramnios was a rather weak predictor of poor perinatal outcome.

Oligohydramnios in Uncomplicated Pregnancies beyond 40 Completed Weeks

OBJECTIVES

In low-risk pregnancies, the management of oligohydramnios is not clear. The aim of this study was to compare maternal and neonatal outcomes in cases of isolated oligohydramnios randomised to either induction of labour or expectant management.

METHODS

87 women pregnant beyond 40 completed weeks were asked to participate in the study. Fifty-four accepted and were randomised at 288 days of pregnancy. Twenty-six were randomised to expectant management and 28 to induction of labour. The primary maternal outcome was the mode of delivery and the primary neonatal outcomes were cord blood pH and Apgar score at delivery.

RESULTS

No significant differences were found for any important maternal or neonatal outcome.

CONCLUSION

Based on these results, the decisions about management could be individualised. Even though the number of patients included was small, these results are well in concordance with others.

Amniotic fluid index vs single deepest pocket technique during modified biophysical profile: a randomized clinical trial

OBJECTIVE

The purpose of this study was to determine the superior technique, if either, of the amniotic fluid index (AFI) vs the single deepest pocket technique in predicting an adverse pregnancy outcome among high-risk patients undergoing antenatal testing.

STUDY DESIGN

Patients having modified biophysical profile (nonstress test plus sonographic estimation of amniotic fluid) were randomized to either have AFI or determination of the presence or absence of a 2 x 1-cm single deepest pocket.

RESULTS

Between January of 1997 and December of 2001, 1080 women were randomized with 530 women in the AFI arm, and 558 in the 2 x 1 pocket arm. The maternal demographics and prenatal complications were similar between groups. Significantly more patients were identified as having oligohydramnios using AFI (17%) compared with using 2 x 1 pocket (10%) ( P =.002). The overall rate of cesarean section for nonreassuring fetal heart rate (FHR) tracing was 3.8% (30 cases, with 16 cases in the AFI-monitored, and 14 cases in the 2 x 1 pocket-monitored groups, respectively, P =.608). Logistic regression analysis showed no difference between the groups with respect to the ability to identify patients who underwent cesarean section for nonreassuring FHR tracing during labor ( P =.999). The umbilical artery pH <7.1 ( P =.688) and admission to the newborn intensive care unit were also comparable between groups.

CONCLUSION

During antepartum fetal surveillance, use of single deepest pocket compared with amniotic fluid index is associated with a significantly lower rate of suspected oligohydramnios.

Biophysical profile with amniotic fluid volume assessments

OBJECTIVE

To compare the amniotic fluid index (AFI) with the single deepest pocket technique along with the other components of the biophysical profile (BPP) in predicting an adverse pregnancy outcome.

METHODS

Prospective, randomized trial of amniotic fluid assessment by AFI or single deepest pocket during a BPP. Cesarean delivery for fetal distress was the primary outcome evaluated.

RESULTS

The AFI was used in 273 pregnancies and the single deepest pocket in 264. The AFI significantly increased the number of pregnancies labeled as oligohydramnios, 102 women (38%) compared with 46 women (17%; P <.001), odds ratio (OR) = 2.84, 95% confidence interval 1.90-4.25 in the single deepest pocket group. There was no difference in the number of women with oligohydramnios in the AFI group, 16 of 102 (16%), undergoing a cesarean delivery for fetal intolerance of labor compared with the single deepest pocket group, 6 of 46 (13%; P =.676). More women with normal fluid by the AFI method (AFI > 5), 20 of 170 (12%), underwent a cesarean delivery for fetal distress than the women with normal fluid by the single deepest pocket technique (2 cm x 1 cm pocket present) group, 12 of 218 (6%; P =.037, OR = 2.22, 95% confidence interval 1.05-4.70).

CONCLUSION

The AFI offers no advantage in detecting adverse outcomes compared with the single deepest pocket when performed with the BPP. The AFI may cause more interventions by labeling twice as many at-risk pregnancies as having oligohydramnios than with the single deepest pocket technique.

A randomized clinical trial of the intrapartum assessment of amniotic fluid volume: amniotic fluid index versus the single deepest pocket technique

OBJECTIVE

The purpose of this study was to determine whether an intrapartum assessment of amniotic fluid identifies a pregnancy that is at risk for an adverse outcome.

STUDY DESIGN

Parturients who were admitted for delivery were assigned randomly to have the amniotic fluid assessed either by amniotic fluid index or by the presence of a 2 x 1 pocket.

RESULTS

The amniotic fluid index was obtained in 499 pregnancies, and the 2 x 1 technique was performed in 501. Oligohydramnios was diagnosed in 25% of amniotic fluid index pregnancies versus 8% with the use of the 2 x 1 pocket technique (P <.001). Both techniques failed to identify patients who underwent an amnioinfusion for fetal distress (P=.864) or who experienced variable (P=.208) or late decelerations (P=.210) that influenced delivery, fetal distress in labor (P=.220), caesarean delivery for fetal distress (P=.133), and admission to neonatal intensive care unit (P=.686).

CONCLUSION

Neither the amniotic fluid index nor the 2 x 1 pocket technique that was undertaken as a fetal admission test identifies a pregnancy that is at risk for an adverse outcome.

Isolated oligohydramnios is not associated with adverse perinatal outcomes

OBJECTIVE

To examine fetal growth and perinatal outcomes in pregnancies with isolated oligohydramnios.

DESIGN

A cohort study.

SETTING

Multiple clinics and hospitals.

POPULATION

Low risk pregnant women.

METHODS

We used data from the multicentre clinical trial of Routine Antenatal Diagnostic Imaging with UltraSound (RADIUS), in which 15,151 low risk pregnant women were randomly assigned to the ultrasound screening group or the control group. Women in the screening group underwent sonographic exams at 15-22 and 31-35 weeks of gestation. Both groups could have clinically indicated sonographic exams at any time.

MAIN OUTCOME MEASURES

We used changes of fetal weight z-score to assess whether fetal growth was compromised from the diagnosis of oligohydramnios until delivery, using a repeated-measures regression. We used a combined perinatal index as an indicator of adverse perinatal outcome, which consisted of severe perinatal morbidity and mortality.

RESULTS

Oligohydramnios (amniotic fluid index < or =5 cm) was diagnosed in 1.5% (113/7617) of women with ultrasound screening compared with 0.8% (57/7534) among the controls. Approximately half of the oligohydramnios cases in the screening group were isolated with no clearly associated factors (e.g. premature rupture of the fetal membranes, congenital anomalies, diabetes, hypertension, postdate and intrauterine growth restriction). Fetal weight centiles in isolated oligohydramnios cases did not change significantly from diagnosis until delivery. Pregnancies with isolated oligohydramnios had perinatal outcomes similar to pregnancies with a normal amniotic fluid index.

CONCLUSION

Isolated oligohydramnios is not associated with impaired fetal growth or an increased risk of adverse perinatal outcomes.

An amniotic fluid index < or =5 cm within 7 days of delivery in the third trimester is not associated with decreasing umbilical arterial pH and base excess

OBJECTIVE

To determine if an amniotic fluid index (AFI) < or =5.0 cm within 7 days of delivery in the third trimester is associated with decreasing umbilical arterial pH and base excess.

STUDY DESIGN

Cases for this retrospective cohort study were all pregnancies > or =26 weeks with intact membranes and an AFI < or =5.0 cm within 7 days of delivery between 11/99 and 7/02. Multiple gestations, aneuploid, and anomalous fetuses were excluded. Controls with an AFI >5.0 cm within 7 days of delivery were matched to each case within 1 week by gestational age. For a control group with a mean+/-SD umbilical arterial pH of 7.26+/-0.07 and alpha=0.05, a sample size of 100 would have a power of 99% to detect a difference with a study group whose mean was 7.20. Data were compared using paired Student's t-test, Mann-Whitney, Fisher's exact, chi(2) and risk ratios with 95% confidence intervals.

RESULTS

In all, 131 neonates with an AFI < or =5.0 cm were matched to 131 controls with an AFI >5 cm. There was no difference in gestational age (37.6+/-3.0, 37.7+/-3.0 weeks) or birth weight (2897+/-810, 2762+/-788 g). There was no difference in umbilical artery pH (7.25+/-0.07, 7.26+/-0.07) or base excess (-3.32+/-2.59, -2.83+/-2.45 mmol/l), even in small for gestational age (SGA) infants in both groups. There was no difference in the number of SGA neonates, 5-minute Apgar <7, respiratory distress syndrome, necrotizing enterocolitis, or neurologic morbidity. Linear regression showed no correlation between AFI and either umbilical arterial pH (r=-0.00047, SE=0.001, p=0.63) or base excess (r=-0.029, SE=0.037, p=0.428).

CONCLUSION

An AFI < or =5.0 cm measured within 7 days of delivery in the third trimester is not associated with decreasing umbilical arterial pH and base excess.

Multiple assessment techniques evaluate antepartum fetal risks

As technology has advanced, the field of antepartum fetal evaluation has grown. As reviewed here, a variety of options are available for use in the complicated pregnancy, including application of fetal heart rate monitoring techniques, noninvasive assessment of amniotic fluid volume, sonographic evaluation of fetal behavior, and Doppler assessment of fetal blood flow. It remains unclear which test is the best for any particular situation. The NST is the simplest test to perform but has a higher false-positive rate than the biophysical profile or the CST. These two tests also appear to demonstrate superior sensitivity, at the expense of increased testing time and cost. The application of vibroacoustic stimulation improves the specificity of the NST, while the addition of a sonographic assessment of amniotic fluid volume increases sensitivity and creates an acceptable alternative as a primary test. The limited biophysical profile, with the NST component initially omitted, provides some savings in time and cost without apparent loss of sensitivity or specificity when compared with the full profile. Ultimately, while one particular technique of fetal assessment may never prove to be the best, certain techniques may have advantages over others in particular clinical situations. Umbilical artery Doppler velocimetry appears to be a useful adjunct to other forms of testing, especially in the pregnancy at risk for intrauterine growth restriction and pre-eclampsia. Recent data have shown the biophysical profile predicts the onset of amnionitis in the setting of preterm premature rupture of membranes (PROM). The sonographic assessment of amniotic fluid volume is particularly important in the serial evaluation of the pregnancy complicated by fetal growth restriction. As new technology leads to innovative forms of testing, it is expected that these new tests of fetal status will similarly add to, rather than replace, the existing items in our armamentarium.

Cesarean delivery for fetal distress: rate and risk factors

The objective of this article was to review the recent English language literature on cesarean delivery for fetal distress to determine its incidence, diagnostic tests, and the contributing factors to this obstetric complications. A PubMed search (1990-2000) with items of "cesarean, fetal distress," "cesarean, non-reassuring fetal heart rate," "cesarean, neonatal acidosis," and "cesarean, umbilical arterial pH," was undertaken. Reports, letters to the editor, focus on anomalous fetuses, and papers not specifically focused on this topic were excluded. Of the 392 articles that the search yielded, 169 met the inclusion criteria. Based on 37 reports with more than 1,000 patients each, the overall risk of prompt cesarean delivery for fetal concern was 3.1% (43,340 of 13,989,74). The risk exceeded 20% in patients with moderate/severe asthma, severe hypothyroidism, severe preeclampsia, and postterm or fetal growth restricted fetuses with abnormal Doppler studies. Use of likelihood ratios suggests that Doppler of the umbilical artery is a superior diagnostic test to amniotic fluid index in identifying parturients at risk for cesarean for non-reassuring fetal heart rate tracing. Although several risk factors increase the need for cesarean delivery for fetal distress, in general, most are unpreventable.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader will be able to estimate the incidence of cesarean delivery for non-reassuring fetal heart rate tracing, outline potential diagnostic tests that are useful for the detection of fetal distress, and summarize medical and obstetric conditions that place patients at risk for cesarean delivery for fetal distress.

Comparability of the amniotic fluid index and single deepest pocket measurements in clinical practice

Two ultrasound techniques, the amniotic fluid index (AFI) and the single deepest pocket (SDP), are currently used to detect oligohydramnios, predict variable decelerations, risk of Caesarean delivery for fetal distress, Apgar scores, umbilical cord artery pH, perinatal mortality, and cerebral palsy. Both techniques poorly identify oligohydramnios. Both techniques identify pregnancies at risk for variable decelerations, low Apgar scores, and Caesarean delivery for fetal distress. Only the SDP is predictive of a compromised fetus-umbilical artery pH, as a stand-alone test, has been correlated with perinatal mortality, and as part of the biophysical profile has been linked to cerebral palsy. This brief communication reviews the comparability of these two techniques and which method, if either, is superior in the identification of oligohydramnios, the predictability of these techniques to identify an adverse pregnancy outcome, and the ability to predict cerebral palsy and perinatal mortality.

Is there a relationship between fetal weight and amniotic fluid index?

OBJECTIVE

To establish whether there is a relationship between the amniotic fluid index and estimated fetal weight in the third trimester. The presence of a relationship would require adjustment of amniotic fluid index to take account of estimated fetal weight with potential improvement in its prediction of adverse perinatal outcomes.

METHODS

Paired measurements of amniotic fluid index and estimated fetal weight from 274 low-risk pregnancies enrolled in a longitudinal study of fetal growth. Measurements were made at fortnightly intervals from 30 weeks' gestation until delivery. A relationship between amniotic fluid index and estimated fetal weight was sought at gestational age week intervals of 30-32, 33-35, 36-38 and 39-41.

RESULTS

One thousand and three pairs of measurements of amniotic fluid index and estimated fetal weight were available for analysis. Mean amniotic fluid index decreased towards term as expected. There was no correlation between amniotic fluid index and estimated fetal weight. Furthermore, there was no correlation between amniotic fluid index and estimated fetal weight at any of the gestational age intervals.

CONCLUSIONS

There is no clinically relevant correlation between amniotic fluid index and estimated fetal weight. It should remain clinical practice to take account of gestational age when interpreting amniotic fluid index but it is not necessary to make adjustments for estimated fetal weight.

Low amniotic fluid index as a predictor of adverse perinatal outcome

OBJECTIVE

To determine whether an antepartum amniotic fluid index (AFI) of 5.0 cm or less is a predictor of adverse perinatal outcome.

STUDY DESIGN

The antepartum testing records of 779 women seen over a 12-month period were reviewed. Data, including the reasons for testing, the testing results, and pregnancy outcome were abstracted from these records. Inclusion criteria included a nonanomalous fetus and delivery within 7 days of the last antepartum surveillance test (modified biophysical profile). Chi-square analysis, Fisher's exact test, t tests and receiver-operator curves (ROCs) were used for analysis.

RESULTS

An AFI of 5.0 cm or less was significantly associated with an abnormal antepartum fetal heart rate (FHR) tracing but not with cesarean delivery, meconium-stained fluid, Apgars less than 7, or NICU admission. Subjects with an AFI of 5.0 cm or less had a higher rate of cesarean for fetal distress, but this did not reach statistical significance. ROCs produced no diagnostic cutoff values for AFI or largest pocket and prediction of any of the chosen parameters.

CONCLUSIONS

Antepartum oligohydramnios is associated with an increased risk of fetal heart rate abnormalities. Although in our population it is not predictive of adverse perinatal outcome as measured by low Apgars and NICU admissions, this may be reflective of the aggressive antepartum and intrapartum management that these patients received.

Prolonged pregnancy

Prolonged pregnancy is defined as any pregnancy that lasts 294 days or more. It is now well recognized that prolonged pregnancy is associated with an increased risk of perinatal mortality and morbidity. It is these complications of pregnancy that have led obstetricians to adopt a policy of induction of labour before the onset of the post-term period. The induction of labour between 41 and 42 weeks is, however, a very crude strategy for reducing term and post-term stillbirth rates. Although the risk of fetal death is increased after 42 weeks, many more fetuses die in utero between 37 and 42 weeks than die in the post-term period. It appears that smaller term fetuses run a greater risk than their larger counterparts, and that current methods of antepartum assessment of the term fetus are still inadequate. It behoves us as obstetricians to improve our capabilities in identifying the compromised fetus at term. This review puts into perspective the most recent publications and highlights areas requiring further study.

The amniotic fluid index, single deepest pocket, and two-diameter pocket in normal human pregnancy

OBJECTIVE

This study was undertaken to determine normative values for amniotic fluid index, single deepest pocket, and 2-diameter pocket across gestation.

STUDY DESIGN

Fifty patients with normal pregnancies at each gestational age between 14 and 41 weeks' gestation were recruited prospectively and scanned once. Data were transformed into logarithmic (base 10) values for analysis. Polynomial regression equations were used to predict the normal values for amniotic fluid index, single deepest pocket, and 2-diameter pocket across gestational age and to predict the weekly percentage changes.

RESULTS

The mean amniotic fluid index, single deepest pocket, and 2-diameter pocket values were significantly lower among patients at <37 weeks' gestation (n = 1150) than among those at > or =37 weeks' gestation (n = 250; P <.001 for all comparisons). The calculated prevalences of oligohydramnios (amniotic fluid index < or =5 cm, single deepest pocket <2 cm, or 2-diameter pocket <15 cm(2)) were significantly different (P <.0001) for the three techniques (8%, 1%, and 30%, respectively). Hydramnios (amniotic fluid index >24 cm, single deepest pocket >8 cm, or 2-diameter pocket >50 cm(2)) was also diagnosed with significantly different (P <.0001) frequencies (0%, 0.7%, and 3%, respectively).

CONCLUSIONS

This is the largest prospective study to date to provide normative data for each of three ultrasonographic techniques used to assess amniotic fluid volume. The single deepest pocket appears to be the preferable method, because its use is least likely to lead to the false-positive diagnosis of either oligohydramnios or hydramnios.

Amniotic fluid volume assessment in singleton and twin pregnancies

The best method of ultrasonic mensuration to identify abnormal AFV reliably in singletons and the individual sacs of diamniotic twins remains elusive. With respect to twins, localization of the dividing membrane seems to be necessary for AFV assessments of each amniotic cavity. The relationship of ultrasonic estimates, actual AFV, and pregnancy outcome remains undetermined. In the authors' opinion, the subjective assessment in twin gestation may be as accurate as semiquantitative ultrasonic estimates of AFV, similar to the situation in singleton pregnancies. The authors propose that further prospective research address the following questions: (1) What is the appropriate threshold for intervention when AFI decreases to lower ranges? (2) What other factors (e.g., cervical examination, fetal heart rate patterns, underlying obstetric conditions, fetal growth pattern) are important when the AFI falls to low values in making clinical decisions?

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.