Amniotic fluid index measured with the aid of color flow 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.

Addition of Color Doppler Sonography for Detection of Amniotic Fluid Disturbances and Its Implications on Perinatal Outcomes

OBJECTIVES

To determine whether color Doppler sonography increases the detection of pregnancies at risk for adverse outcomes.

METHODS

Participants admitted to labor and delivery with the anticipation of a vaginal delivery underwent measurements of amniotic fluid volume (AFV) using amniotic fluid index (AFI) and single deepest pocket (SDP) techniques by grayscale followed by color Doppler sonography. Oligohydramnios was defined as an AFI of less than 5 cm or an SDP of less than 2 cm. Intrapartum and perinatal outcomes were compared between participants with a diagnosis of a low AFV by grayscale and color Doppler sonography.

RESULTS

Over 42 months, 428 women were enrolled in the study. Color Doppler sonography resulted in lower AFV estimates (mean ± SD by the AFI, 10.7 ± 3.7 cm by grayscale sonography and 8.6 ± 3.6cm by color Doppler sonography; P < .0001). For the SDP, the mean AFVs were 4.6 ± 2.0 cm by grayscale sonography and 3.4 ± 1.4 cm by color Doppler sonography (P < .0001). The level of agreement between grayscale and color Doppler sonography in estimating the AFV was fair, with κ = 0.32 for the AFI and 0.28 for the SDP. Outcome measures of AFVs classified as low based on color Doppler sonography (normal by grayscale sonography) and those classified as low by grayscale sonography (low by color Doppler sonography) were compared. There was no difference in composite perinatal complications, mode of delivery, or composite neonatal complications.

CONCLUSIONS

The use of color Doppler sonography leads to the overdiagnosis of low AFVs and does not appear to increase the detection of pregnancies destined for adverse intrapartum or perinatal outcomes.

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.

Explaining the 2001–2002 Infant Mortality Increase in the United States: Data from the Linked Birth/Infant Death Data Set

The U.S. infant mortality rate (IMR) increased from 6.8 infant deaths per 1,000 live births in 2001 to 7.0 in 2002, the first increase in more than 40 years. From 2001 to 2002, IMR increased for very low birthweight infants as well as for preterm and very preterm infants. Although IMR for very low birthweight infants increased, most of the increase in IMR from 2001 to 2002 was due to a change in the distribution of births by birthweight and, more specifically, to an increase in infants born weighing less than 750 grams. The majority of infants born at less than 750 grams die within the first year of life; thus, these births contribute disproportionately to overall IMR. Increases in births at less than 750 grams occurred for non-Hispanic white, non-Hispanic black, and Hispanic women. Most of the increase occurred among mothers 20 to 34 years of age. Although multiple births contributed disproportionately, most of the increase in births at less than 750 grams occurred among singletons. Three hypotheses were evaluated to assess their possible impact on the increase in less than 750-gram births: possible changes in (1) the reporting of births or fetal deaths, (2) the risk profile of births, and (3) medical management of pregnancy. Although each of these factors may have contributed to the increase, the relative effects of these and other factors remain unclear. More detailed studies are needed to further explain the 2001–2002 infant mortality increase.

Unconditional reference values for the amniotic fluid index measurement between 26w0d and 41w6d of gestation in low-risk pregnancies

OBJECTIVE

To establish reference values for the amniotic fluid index (AFI) measurement between 26w0d and 41w6d of gestation in a Brazilian population.

METHODS

We performed a cross-sectional study with 1984 low-risk singleton pregnant women between 26w0d and 41w6d of gestation. AFI was measured according to the technique proposed by Phelan et al. Maternal abdomen was divided into four quadrants using the umbilicus and linea nigra as landmarks. Single vertical pocket in each quadrant was measured and the AFI was generated by the sum of these four values without umbilical cord or fetal parts. All ultrasound exams were performed by only two experienced examiners. AFI was expressed as median, interquartile range, mean and ranges in each gestational age (GA) interval. Polynomial regressions were performed to obtain the best fit with adjustment by the determination coefficient (R(2)).

RESULTS

Mean of AFI ranged from 14.0 ± 4.1 cm (range, 9.7-14.0) at 26w0d to 8.3 ± 4.7 cm (range, 1.9-16.5) at 41w6d, respectively. The best polynomial regression fit curve was a first-degree: AFI = 16.29-0.125*GA (R(2) = 0.01). According the scatterplot, AFI values practically did not vary with advancing GA.

CONCLUSION

Reference values for the AFI measurement between 26w0d and 41w6d of gestation in a low-risk Brazilian population were established.

Polyhydramnios: Causes, Diagnosis and Therapy

Polyhydramnios is defined as a pathological increase of amniotic fluid volume in pregnancy and is associated with increased perinatal morbidity and mortality. Common causes of polyhydramnios include gestational diabetes, fetal anomalies with disturbed fetal swallowing of amniotic fluid, fetal infections and other, rarer causes. The diagnosis is obtained by ultrasound. The prognosis of polyhydramnios depends on its cause and severity. Typical symptoms of polyhydramnios include maternal dyspnea, preterm labor, premature rupture of membranes (PPROM), abnormal fetal presentation, cord prolapse and postpartum hemorrhage. Due to its common etiology with gestational diabetes, polyhydramnios is often associated with fetal macrosomia. To prevent the above complications, there are two methods of prenatal treatment: amnioreduction and pharmacological treatment with non-steroidal anti-inflammatory drugs (NSAIDs). However, prenatal administration of NSAIDs to reduce amniotic fluid volumes has not been approved in Germany. In addition to conventional management, experimental therapies which would alter fetal diuresis are being considered.

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.