Biophysical profile with amniotic fluid volume assessments

Amniotic fluid volume and pregnancy outcomes in twin pregnancies: A systematic review and meta-analysis

Objective

To analyse amniotic fluid volume (AFV), specifically oligohydramnios or polyhydramnios, and associated pregnancy and neonatal outcomes in twin gestations through systematic review and meta-analysis.

Methods

We utilised systematic review methodology to identify items within published and grey literature resources. Prospective and retrospective studies with a control group were included. Inclusion criteria were as follows: studies in English, twin pregnancy in which AFVs and associated pregnancy and/or neonatal outcomes were evaluated. Exclusion criteria included the presence of an anomalous fetus, chromosome abnormality, monochorionic diamniotic twin pregnancy complicated by twin-twin transfusion syndrome or twin-reversed arterial perfusion, twin gestations undergoing therapeutic interventions (i.e. fetoscopic laser photocoagulation and serial amniocentesis) and monochorionic monoamniotic twin pregnancy.

Results

The literature search identified 1068 abstracts, only four met criteria for inclusion and analysis. The pooled data (two studies per outcome) revealed no significant difference in rate of pre-term delivery (OR: 2.94; CI: 0.20-43.81), pre-term delivery less than 32 weeks (OR: 1.97; CI: 0.43-9.12), umbilical cord pH < 7 (OR: 2.66; CI: 0.22-32.51), rate of stillbirth (OR: 4.13; CI: 0.40-42.70), neonatal death (OR: 1.48; CI: 0.05-43.94), rate of NICU admission (OR: 1.38; CI: 0.61-3.11) or rate of small-for-gestational-age (SGA) infants (OR: 1.39; CI: 0.33-5.94).

Conclusion

Based on the pooled data (two studies per outcome), there was no difference in the fate of pre-term delivery, umbilical cord pH < 7, stillbirth, neonatal death or SGA infants. What is disturbing is the lack of studies (1946-2020) that analysed the association between AFV and pregnancy outcomes in twin pregnancies.

The amniotic fluid index and oligohydramnios: a deeper dive into the shallow end

Second- and third-trimester obstetrical ultrasound examinations include an amniotic fluid volume assessment. Professional organizations' clinical guidance recommends using semiquantitative techniques, such as the single deepest vertical pocket or amniotic fluid index, for this purpose. The single deepest vertical pocket is described as the preferred method of assessing amniotic fluid volume based on fewer oligohydramnios diagnoses and labor inductions with no demonstrable difference in pregnancy outcomes compared with the amniotic fluid index. We offer an alternative interpretation of the evidence for this advice, drawn from 6 randomized clinical trials and 2 meta-analyses comparing the single deepest vertical pocket to the amniotic fluid index. Individually and collectively, these reports are underpowered to detect significant differences in maternal and perinatal outcomes by study group. Moreover, randomized clinical trials comparing maternal and perinatal outcomes resulting from a policy of labor induction at or beyond 37 weeks of gestation vs expectant care consistently favor labor induction, the very intervention paradoxically cited as favoring the single deepest vertical pocket vs the amniotic fluid index. We conclude that the amniotic fluid index should be considered a reasonable method for third-trimester amniotic fluid assessment and diagnosing oligohydramnios.

Amniotic Fluid Volume Assessment: Eight Lessons Learned

Actual AFV can be determined by a dye-dilution technique or be directly measured at cesarean. This allows investigators to correlate estimated and actual AFVs. Lessons learned by assessing the relationship of estimated to actual AFVs. 1) Ultrasound estimates normal actual AFVs well, but abnormal AFVs poorly. 2) Quantile regression is a better statistical methodology to create a normal AFV curve across pregnancy. 3) There is no difference in the accuracy of the subjective (visualization without measurements) compared with the objective (visualization with measurements) technique in identifying normal and abnormal AFVs. 4) Color Doppler use leads to the over-diagnosis of oligohydramnios. 5) Intravenous hydration increases actual AFVs. 6) The estimation of AFV can be done with the transducer held perpendicular to the floor or perpendicular to the uterine contour. 7) The single deepest pocket should be used for identifying low AFVs. 8) The AFI should be used for identifying high AFVs.

Antepartum Fetal Surveillance: ACOG Practice Bulletin, Number 229

The goal of antepartum fetal surveillance is to reduce the risk of stillbirth. Antepartum fetal surveillance techniques based on assessment of fetal heart rate (FHR) patterns have been in clinical use for almost four decades and are used along with real-time ultrasonography and umbilical artery Doppler velocimetry to evaluate fetal well-being. Antepartum fetal surveillance techniques are routinely used to assess the risk of fetal death in pregnancies complicated by preexisting maternal conditions (eg, diabetes mellitus) as well as those in which complications have developed (eg, fetal growth restriction). The purpose of this document is to provide a review of the current indications for and techniques of antepartum fetal surveillance and outline management guidelines for antepartum fetal surveillance that are consistent with the best scientific evidence.

Pharmacological treatment in pregnant women with moderate symptoms of coronavirus disease 2019 (COVID-19) pneumonia

OBJECTIVE

Pregnant women with moderate symptoms of COVID-19 are at risk for progressing to severe or critical illness. While there are limited data on the management of severe COVID-19 during pregnancy, information on pharmacological treatments of moderate COVID-19 is lacking. We report clinical outcomes of pregnant women hospitalized due to moderate COVID-19 illness treated with a 5-day course of remdesivir, antibiotics, and/or glucocorticoids.

MATERIALS AND METHODS

Case series of pregnant women hospitalized with moderate symptoms of COVID -19 pneumonia at two INOVA Health System hospitals from April 1 to December 31, 2020. Primary outcome was clinical recovery (breathing on ambient air and/or hospital discharge) on hospital day 7 (HD7). Cox regression analysis was performed to evaluate which variables were associated with the primary outcome.

RESULTS

Out of 748 pregnant women with confirmed infection by reverse transcriptase polymerase chain reaction, 35 were hospitalized due to moderate symptoms of COVID-19 pneumonia (median gestational age 29 weeks). There was no maternal death. Seventeen patients received remdesivir within 48 hours of hospitalization: 15 remained with moderate symptoms and 2 (who also received glucocorticoids) had progressed to critical COVID-19 at remdesivir initiation; all 17 women in this group achieved clinical recovery on HD7. Seven women received remdesivir >48 hours following admission after they began treatment with glucocorticoids ± antibiotics and worsened to severe or critical disease; they all required supplemental oxygen on HD7. Eleven women were treated with antibiotics ± glucocorticoids but no remdesivir; on HD7, 3/11 achieved clinical recovery. Clinical recovery was significantly different among treatment groups; p < 0.001. When analyzing only women who remained with moderate symptoms at pharmacological treatments initiation, all 15 on remdesivir and only 3 of 11 on antibiotics achieved clinical recovery on HD7; p < 0.001. Delaying remdesivir for >48 hours after admission (HR 2.32, 95% CI 1.45-4.16) and >4-day duration of symptoms prior to hospitalization (HR 1.65, 95% CI 1.27-3.50) had an inverse association with clinical recovery. Incidental oligohydramnios was seen in 3/24 (12.5%) of women within 5 days of completing remdesivir treatment. Elevated transaminases was prevalent in women treated with remdesivir (8/24, 33.3%).

CONCLUSION

In our cohort, prompt initiation of remdesivir in pregnant women hospitalized with moderate symptoms of COVID-19 pneumonia within 48 hours of admission prevented worsening and allowed a fast clinical recovery by HD7. Deferring remdesivir for >48 hours after hospitalization and duration of symptoms >4 days before admission were independently associated with delayed clinical recovery and longer hospital admission. Ultrasound evaluation of the amniotic fluid in patients recovering from COVID-19 hospitalization should be considered.

Diagnostic utility of maximum vertical pocket versus amniotic fluid index in assessing amniotic fluid volume for the prediction of adverse maternal and fetal outcomes: a systematic review and meta-analysis

Objective: To compare the utility of maximum vertical pocket versus amniotic fluid index for predicting adverse perinatal outcomes.Methods: Systematic review of randomized clinical studies comparing these two ultrasound techniques and random-effects meta-analysis to quantify a range of perinatal outcomes.Result: Six studies with 4278 women were eligible. Use of the maximum vertical pocket reduced the rate of diagnosis of oligohydramnios (pooled relative risk 0.38; 95% confidence interval 0.27, 0.53). Use of the maximum vertical pocket was associated with significantly lower rates of non-reassuring fetal heart tracing, cesarean delivery for fetal distress, and induction of labor for oligohydramnios. There were no differences in the rates of cesarean delivery, presence of meconium, umbilical artery pH <7.1, 5-minute Apgar score <7, or admission to the neonatal intensive care unit.Conclusion: The use of maximum vertical pocket is associated with a lower rate of pregnancy intervention without any worsening of adverse pregnancy outcomes.

No. 197a-Fetal Health Surveillance: Antepartum Consensus Guideline

OBJECTIVE

This guideline provides new recommendations pertaining to the application and documentation of fetal surveillance in the antepartum period that will decrease the incidence of birth asphyxia while maintaining the lowest possible rate of obstetrical intervention. Pregnancies with and without risk factors for adverse perinatal outcomes are considered. This guideline presents an alternative classification system for antenatal fetal non-stress testing to what has been used previously. This guideline is intended for use by all health professionals who provide antepartum care in Canada.

OPTIONS

Consideration has been given to all methods of fetal surveillance currently available in Canada.

OUTCOMES

Short- and long-term outcomes that may indicate the presence of birth asphyxia were considered. The associated rates of operative and other labour interventions were also considered.

EVIDENCE

A comprehensive review of randomized controlled trials published between January 1996 and March 2007 was undertaken, and MEDLINE and the Cochrane Database were used to search the literature for all new studies on fetal surveillance antepartum. The level of evidence has been determined using the criteria and classifications of the Canadian Task Force on Preventive Health Care (Table 1).

SPONSOR

This consensus guideline was jointly developed by the Society of Obstetricians and Gynaecologists of Canada and the British Columbia Perinatal Health Program (formerly the British Columbia Reproductive Care Program or BCRCP) and was partly supported by an unrestricted educational grant from the British Columbia Perinatal Health Program. RECOMMENDATION 1: FETAL MOVEMENT COUNTING: RECOMMENDATION 2: NON-STRESS TEST: RECOMMENDATION 3: CONTRACTION STRESS TEST: RECOMMENDATION 4: BIOPHYSICAL PROFILE: RECOMMENDATION 5: UTERINE ARTERY DOPPLER: RECOMMENDATION 6: UMBILICAL ARTERY DOPPLER.

Amniotic Fluid: Technical Update on Physiology and Measurement

OBJECTIVE

OUTCOMES: EVIDENCE: A MEDLINE and KFINDER search was used to identify relevant articles, with review of bibliography identified article including Cochrane reviews and recent review articles.

VALUES

The evidence collected was reviewed by the Diagnostic Imaging Committee of the Society of Obstetricians and Gynecologists of Canada. The recommendations were made according to the guidelines developed by The Canadian Task Force on Preventative Health Care (Table 1).

BENEFITS, HARMS AND COSTS

Amniotic fluid assessment by ultrasound has become an integral part of fetal assessment in modern obstetrics. Abnormalities of fluid volume result in obstetrical intervention and further investigations. In Canada, there are no standard definitions of fluid volume estimation, nor a standard approach to assessing fluid. Multiple randomized trials have suggested that using a Single Pocket Estimation technique (rather than the multi pocket assessment approach known as the amniotic fluid index), will result in fewer obstetrical interventions without any increase in adverse outcomes. Recent literature suggests that there are detectable, modest changes in amniotic fluid that can occur within an hour or two of normal physiological maneuvers. This may account for the variability and inconsistent results from repeated assessments within a short period of time which can lead to confusion and generate further testing. This article hopes to describe the limitations of amniotic fluid assessment, promote a standard method of amniotic fluid assessment, and propose a common set of definitions to be used to describe amniotic fluid volume.

SUMMARY STATEMENTS

RECOMMENDATION.

Mise à jour technique sur la physiologie et l'évaluation du liquide amniotique

OBJECTIF

RéSULTATS: SOURCES DES DONNéES PROBANTES: Nous avons effectué une recherche sur MEDLINE et Kfinder pour trouver des articles pertinents, puis avons examiné les bibliographies des articles retenus, notamment des revues Cochrane et des articles de revue récents.

VALEURS

Les données recueillies ont été analysées par le Comité d'imagerie diagnostique de la Société des obstétriciens et gynécologues du Canada. Les recommandations ont été classées selon les critères établis par le Groupe d'étude canadien sur les soins de santé préventifs (Tableau 1). AVANTAGES, DéSAVANTAGES ET COûTS: En obstétrique moderne, l'évaluation du volume de liquide amniotique par échographie fait partie intégrante de l'évaluation fœtale. Toute anomalie donne lieu à une intervention obstétricale et à des examens approfondis. Au Canada, il n'existe aucune définition normalisée associée à l'estimation du volume de liquide amniotique ni aucune approche d'évaluation uniforme. Plusieurs essais randomisés semblent indiquer que l'évaluation de poche unique, plutôt que de plusieurs poches (indice de liquide amniotique), diminue les interventions obstétricales sans augmenter l'incidence de résultats indésirables. La littérature récente laisse croire que des changements légers, mais détectables du liquide amniotique peuvent survenir une heure ou deux suivant des manœuvres physiologiques normales, ce qui pourrait expliquer la variabilité et le manque de cohérence des résultats d'évaluations répétées en peu de temps et ainsi créer de la confusion et donner lieu à d'autres examens. Le présent article vise à décrire les limites de l'évaluation du volume de liquide amniotique, à promouvoir une méthode d'évaluation normalisée et à proposer un ensemble commun de définitions. DéCLARATIONS SOMMAIRES: RECOMMANDATION.

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.

Single deepest vertical pocket or amniotic fluid index as evaluation test for predicting adverse pregnancy outcome (SAFE trial): a multicenter, open-label, randomized controlled trial

OBJECTIVE

To determine whether the amniotic fluid index (AFI) or the single deepest vertical pocket (SDP) technique for estimating amniotic fluid volume is superior for predicting adverse pregnancy outcome.

METHODS

This was a multicenter randomized controlled trial including 1052 pregnant women with a term singleton pregnancy across four hospitals in Germany. Women were assigned randomly, according to a computer-generated allocation sequence, to AFI or SDP measurement for estimation of amniotic fluid volume. Oligohydramnios was defined as AFI ≤ 5 cm or the absence of a pocket measuring at least 2 × 1 cm. The diagnosis of oligohydramnios was followed by labor induction. The primary outcome measure was postpartum admission to a neonatal intensive care unit. Further outcome parameters were the rates of diagnosis of oligohydramnios and induction of labor (for oligohydramnios or without specific indication), and mode of delivery.

RESULTS

Postpartum admission to a neonatal intensive care unit was similar between groups (4.2% (n = 21) vs 5.0% (n = 25); relative risk (RR), 0.85 (95% CI, 0.48-1.50); P = 0.57). In the AFI group, there were more cases of oligohydramnios (9.8% (n = 49) vs 2.2% (n = 11); RR, 4.51 (95% CI, 2.2-8.57); P < 0.01) and more cases of labor induction for oligohydramnios (12.7% (n = 33) vs 3.6% (n = 10); RR, 3.50 (95% CI, 1.76-6.96); P < 0.01) than in the SDP group. Moreover, an abnormal cardiotocography was seen more often in the AFI group than in the SDP group (32.3% (n = 161) vs 26.2% (n = 132); RR, 1.23 (95% CI, 1.02-1.50); P = 0.03). The other outcome measures were not significantly different between the two groups.

CONCLUSIONS

Use of the AFI method increased the rate of diagnosis of oligohydramnios and labor induction for oligohydramnios without improving perinatal outcome. The SDP method is therefore the favorable method to estimate amniotic fluid volume, especially in a population with many low-risk pregnancies. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

A comparison between amniotic fluid index and the single deepest vertical pocket technique in predicting adverse outcome in prolonged pregnancy

OBJECTIVE

to compare perinatal outcome in induced postterm pregnancies with normal amniotic volume and in patients with prolonged pregnancy undergone induction for oligohydramnios, evaluated by two different ultrasonographic methods.

METHODS

amniotic fluid volume was measured, using Single Deepest Vertical Pocket (SDVP) and Amniotic Fluid Index (AFI), in 961 singleton uncomplicated prolonged pregnancies. In 109 of these patients, hospitalization was planned for induction of labor, during or after 42 weeks of gestation, for oligohydramnios, postterm pregnancy and other indications in 47, 51 and 11 cases, respectively. Perinatal outcome included: rate of caesarean section, fetal distress, non reassuring fetal heart tracing, presence of meconium, umbilical artery pH < 7.1, Apgar score at 5 minutes < 7, admission to neonatal intensive care unit (NICU).

RESULTS

oligohydramnios was diagnosed in 4.89% of cases, when at least one of the two methods was used. A reduced AFI and SDVP value identified 4.47% and 3.75% of cases, respectively, even if without statistical difference. No statistical differences were reported in perinatal outcomes in postterm versus prolonged pregnancies with oligohydramnios, also in relation to the two different ultrasonographic methods.

CONCLUSIONS

oligohydramnios is more frequently diagnosed using AFI than SDVP, consequently determining a higher rate of induction of labor. Moreover, perinatal outcome in prolonged induced pregnancies is not affected by oligohydramnios.

Effect of maternal hydration on the amniotic fluid volume during maternal rest in the left lateral decubitus position: a randomized prospective study

OBJECTIVES

The purpose of this study was to evaluate the effect of maternal hydration on amniotic fluid volume during maternal rest in the left lateral decubitus position.

METHODS

Pregnant women (n = 79) with an amniotic fluid index between 6 and 24 cm and a singleton uncomplicated pregnancy at 35 to 40 weeks' gestation were randomized into hydration and control groups. Starting 30 minutes before the measurements, the hydration group drank 250 mL of water at 15-minute intervals (1000 mL/h). After the initial amniotic fluid index measurements, the women in both groups were instructed to rest in the left lateral decubitus position, and the measurements were repeated at 15, 30, 45, 60, 75, and 90 minutes.

RESULTS

The amniotic fluid index increased at each interval in both groups. Although each amniotic fluid index value was higher than the preceding one, only the 15- and 30-minute values in the left lateral decubitus position alone and the 15-, 30-, and 45-minute values in the left lateral decubitus position with maternal hydration were significantly higher than the preceding measurements (P < .05). A similar increase in the amniotic fluid volume was present 15 minutes after assuming the left lateral decubitus position in both groups. However, after 30 minutes, the women in the left lateral decubitus position without maternal hydration needed another 60 minutes for a significant amniotic fluid index increase, whereas the women with maternal hydration needed only another 45 minutes for a significant increase.

CONCLUSIONS

Maternal rest in the left lateral decubitus position with hydration and maternal rest in the left lateral decubitus position alone caused similar increases in the estimated amniotic fluid volume at 15 minutes. However, after 30 minutes, the amniotic fluid volume increased more rapidly in the group with hydration.

Correlation between the duration of maternal rest in the left lateral decubitus position and the amniotic fluid volume increase

OBJECTIVES

The purpose of this study was to show the relationship between amniotic fluid volume changes and the duration of maternal rest in the left lateral decubitus position.

METHODS

Pregnant women (n = 34) with an amniotic fluid index between 6 and 24 cm and an uncomplicated singleton pregnancy at 35 to 40 weeks' gestation were included in the study. After the initial amniotic fluid index measurements, the women were instructed to rest in the left lateral position, and the measurements were repeated at 15, 30, 45, 60, 75, and 90 minutes.

RESULTS

The amniotic fluid index increased at each sequential interval. Although each amniotic fluid index value was higher than the preceding one, only the 15- and 30-minute values were significantly higher than the preceding measurements (P < .001; P < .01, respectively). At the beginning of maternal rest in the left lateral position, 15 minutes of rest was sufficient to create significant changes (P < .001). However, after 30 minutes of rest, an additional 45 minutes was needed to create a significant amniotic fluid index increase (P < .01). The curve describing the amniotic fluid index increases caused by maternal rest resembled a saturation curve, and the maximum increase in the amniotic fluid volume was projected to be achieved approximately at the end of the second hour of the rest period.

CONCLUSIONS

The correlation between the duration of maternal rest and amniotic fluid volume changes is not linear. However, maternal rest in the left lateral decubitus position significantly increases the amniotic fluid volume, particularly in the first 30 minutes (maximum increase in the first 15 minutes).

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.

Management of oligohydramnios in pregnancy

The finding of oligohydramnios in pregnancy is problematic. The various mechanisms that control amniotic fluid, the inability to precisely measure and quantify the amount, and the relevance of a "decreased" amount of fluid make the management of this finding unclear. Given the limited amount of data, the single deepest vertical pocket may be a better method than the amniotic fluid index to define oligohydramnios. A large prospective study is needed to develop the most optimal management recommendations, especially for idiopathic oligohydramnios at or near term.

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.

Antenatal fetal assessment: contraction stress test, nonstress test, vibroacoustic stimulation, amniotic fluid volume, biophysical profile, and modified biophysical profile--an overview

Antenatal fetal assessment was introduced into the United States in the 1970s. The initial antepartum test, the oxytocin challenge test, later renamed as the contraction stress test, became the gold standard for fetal surveillance. Its labor intensive requirements and contraindications made it inapplicable to some high-risk pregnancies. Other testing schemes were developed subsequently, the nonstress test and its alternative, vibroacoustic stimulation, the semiquantitative assessment of amniotic fluid volume, the biophysical profile and its modified version, the modified biophysical profile. This article is a brief critical review of these testing methods and focuses on the following: (1) physiologic bases; (2) testing methodologies; (3) supportive evidence from randomized controlled and observational trials; and (4) areas needing further investigation.

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.

Biophysical profile for fetal assessment in high risk pregnancies

BACKGROUND

A biophysical profile (BPP) includes ultrasound monitoring of fetal movements, fetal tone and fetal breathing, ultrasound assessment of liquor volume with or without assessment of the fetal heart rate. The BPP is performed in an effort to identify babies that may be at risk of poor pregnancy outcome, so that additional assessments of wellbeing may be performed, or labour may be induced or a caesarean section performed to expedite birth.

OBJECTIVES

To assess the effects of the BPP when compared with conventional monitoring (CTG only or MBPP) on pregnancy outcome in high-risk pregnancies.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (October 2007), CENTRAL (The Cochrane Library 2006, Issue 4), MEDLINE (1966 to November 2006), EMBASE (1974 to November 2006) and CINAHL (1980 to November 2006).

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials involving a comparison of fetal BPP with other forms of antepartum fetal assessment in women with high-risk pregnancies.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed eligibility, quality and extracted data.

MAIN RESULTS

We included five trials, involving 2974 women. Most trials were not of high quality. Although the overall incidence of adverse outcomes was low, available evidence from randomised controlled trials does not support the use of BPP as a test of fetal wellbeing in high-risk pregnancies. We found no significant differences between the groups in perinatal deaths (relative risk (RR) 1.33, 95% confidence interval (CI) 0.60 to 2.98) or in Apgar score less than seven at five minutes (RR 1.27, 95% CI 0.85 to 1.92). Combined data from the two high-quality trials suggest an increased risk of caesarean section in the BPP group RR 1.60, 95% CI 1.05 to 2.44, n = 280, interaction test P = 0.03. However, the number of participating women was relatively small (n = 280). Therefore, additional evidence is required in order to be definitive regarding the efficacy of this test in high-risk pregnancies. Furthermore, the impact of the BPP on other interventions, length of hospitalisation, serious short-term and long-term neonatal morbidity and parental satisfaction requires further evaluation.

AUTHORS' CONCLUSIONS

At present, there is insufficient evidence from randomised trials to support the use of BPP as a test of fetal wellbeing in high-risk pregnancies.

A comparison of 3 criteria of oligohydramnios in identifying peripartum complications: a secondary analysis

OBJECTIVE

The objective of the study was to ascertain the diagnostic accuracy of 3 criteria of oligohydramnios in identifying 4 peripartum complications.

STUDY DESIGN

The 3 definitions of oligohydramnios were amniotic fluid index (AFI) 5.0 cm or less and AFI <5% for gestational age (GA) using nomograms by Moore and Cayle or Magann et al. Likelihood ratio (LR) and guidelines by the Evidence-Based Medicine Working Group were used in the secondary analysis of previously published reports. AFI obtained during antepartum and intrapartum periods were analyzed separately.

RESULTS

The 95% confidence intervals for the prevalence of oligohydramnios using the 3 criteria are significantly different in the antepartum or intrapartum analysis. The LR was <6 for ante- and intrapartum AFI to identify cesarean delivery for nonreassuring fetal heart rate tracing, Apgar score 3 or less at 5 minutes, umbilical arterial pH <7.00, and newborns' weight 5% or less for GA.

CONCLUSION

The 3 criteria for determining the adequacy of amniotic fluid are not fungible, and they are not useful diagnostic tests for identifying peripartum complications because LR is <10.

The ultrasound estimation of amniotic fluid volume in diamniotic twin pregnancies and prediction of peripartum outcomes

OBJECTIVE

To determine ultrasonic estimations of amniotic fluid in diamniotic twins across gestation using the single deepest pocket (SDP) technique and correlate volumes to intrapartum and neonatal outcomes.

STUDY DESIGN

Prospective observational study using diamniotic dichorionic and diamniotic monochorionic pregnancies. Intrapartum and neonatal outcomes were evaluated.

RESULTS

Between April 2004 and April 2006, 299 women were recruited. There was no significant relationship between SDP and gestational age. Statistically significant differences by SDP groups (for low, normal, and high volumes) include preterm delivery (P = .043; 56, 62, and 86%), abnormal labor tracing (P = .013; 5, 8, and 27%), fetal labor intolerance (P = .026; 6, 9, and 27%), Apgar scores at 5 minutes (P = .028; 17, 10, and 27%) and any neonatal complications (P = .002; 28, 21, and 55%).

CONCLUSION

The SDP is constant between 17 and 37 weeks. Fetal labor intolerance and adverse neonatal outcomes are greater in a twin with hydramnios.