The amniotic fluid index in normal human pregnancy

Perinatal outcome and amniotic fluid index in the antepartum and intrapartum periods: A meta-analysis

OBJECTIVE

Our purpose was to perform a meta-analysis of studies on the risks of cesarean delivery for fetal distress, 5-minute Apgar score <7, and umbilical arterial pH <7.00 in patients with antepartum or intrapartum amniotic fluid index >5.0 or <5.0 cm.

STUDY DESIGN

Using a MEDLINE search, we reviewed all studies published between 1987 and 1997 that correlated antepartum or intrapartum amniotic fluid index with adverse peripartum outcomes. The inclusion criteria were studies in English that associated at least one of the selected adverse outcomes with an amniotic fluid index of </=5.0 cm versus >5.0 cm. Contingency tables were constructed for each study, and relative risks and standard errors of their logs were calculated. Fixed-effects pooled relative risks were calculated for groups of studies that were homogeneous, whereas random-effects pooled relative risks were calculated for significantly heterogeneous groups of studies.

RESULTS

Eighteen reports describing 10,551 patients met our inclusion criteria. An antepartum amniotic fluid index of </=5.0 cm, in comparison with >5.0 cm, is associated with an increased risk of cesarean delivery for fetal distress (pooled relative risk, 2.2; 95% confidence interval, 1.5-3.4) and an Apgar score of <7 at 5 minutes (pooled relative risk, 5.2; 95% confidence interval, 2.4-11.3). An intrapartum amniotic fluid index of </=5.0 cm is also associated with an increased risk of cesarean delivery for fetal distress (pooled relative risk, 1.7; 95% confidence interval, 1.1-2.6) and an Apgar score <7 at 5 minutes (pooled relative risk, 1.8; 95% confidence interval, 1.2-2.7). A poor correlation between the amniotic fluid index and neonatal acidosis was noted in the only study that examined this end point. More than 23,000 patients are necessary to demonstrate that the incidence of umbilical arterial pH <7.00 is 1.5 times higher among those with oligohydramnios in labor than among those with adequate amniotic fluid index (alpha = 0.05; beta = 0.2)

CONCLUSIONS

An antepartum or intrapartum amniotic fluid index of </=5.0 cm is associated with a significantly increased risk of cesarean delivery for fetal distress and a low Apgar score at 5 minutes. There are few reports linking amniotic fluid index and neonatal acidosis, the only objective assessment of fetal well-being. A multicenter study with sufficient power should be undertaken to demonstrate that a low amniotic fluid index is associated with an umbilical arterial pH <7.00.

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?

Effect of fetal presentation on the amniotic fluid index

OBJECTIVE

The aim of this study was to determine whether the amniotic fluid index differs according to whether a fetus is in breech or cephalic presentation.

STUDY DESIGN

Between January 1995 and April 1996 the amniotic fluid index was measured both immediately before and after attempted external cephalic version. Amniotic fluid indexes were measured by a senior obstetric resident or attending physician. Preprocedure amniotic fluid indexes and change in amniotic fluid index after successful and failed external cephalic version were compared with unpaired and paired Student t tests, respectively. P <.05 was considered statistically significant.

RESULTS

Thirty consecutive women between 36 and 40 weeks' gestation with breech presentations were evaluated before undergoing an attempt at external cephalic version. The preprocedure amniotic fluid index was not different (P =.61) between women who had success (12.1 cm) and failure (11.4 cm) of attempts at external cephalic version. Successful external cephalic version was associated with a statistically significant increase (P <.0001) in amniotic fluid index with respect to gestations with a persistent breech presentation (3.14 vs -0.35).

CONCLUSION

Successful version from a breech to a cephalic presentation resulted in a significant increase in the amniotic fluid index. This should be considered when a breech presentation with a low normal amniotic fluid index is evaluated. Presentation of the fetus should be considered in evaluating amniotic fluid index distribution curves.

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.

Perinatal risks associated with borderline amniotic fluid index

OBJECTIVE

Our purpose was to determine whether a borderline amniotic fluid index observed during antepartum testing confers a significant risk of adverse perinatal outcome.

STUDY DESIGN

We conducted a retrospective review of all patients entering antepartum testing at Los Angeles County-University of Southern California Women's and Children's Hospital during a 4-month period beginning January 1, 1996. Women with singleton pregnancies who underwent antepartum testing within 1 week of delivery and who were delivered at our institution were identified for our study. An amniotic fluid index >5 and <10 cm was defined as "borderline" and an amniotic fluid index of 10 to 24 cm was considered normal. Markers of adverse perinatal outcome included intrapartum fetal distress, 5-minute Apgar score <7, meconium-stained amniotic fluid, and intrauterine growth restriction.

RESULTS

There was a 2-fold increase in the incidence of adverse perinatal outcome among the women with borderline amniotic fluid index in comparison with control subjects with normal amniotic fluid volume. This difference reflected a 4-fold increase in the incidence of fetal growth restriction among women with a borderline amniotic fluid index.

CONCLUSIONS

A borderline amniotic fluid index observed in antepartum testing is associated with an increased risk of intrauterine growth restriction and overall adverse perinatal outcome. These observations suggest that borderline amniotic fluid index merits twice-weekly antepartum testing.

Application of a semiautomatic boundary detection algorithm for the assessment of amniotic fluid quantity from ultrasound images

The aim of this study was to develop a computer-assisted method to evaluate amniotic fluid volume (AFV). This was done by automatically detecting the boundaries of the amniotic fluid portion in 2-D ultrasonographic images. The study population consisted of 36 low-risk patients that were selected at random from a healthy population undergoing routine pregnancy follow-up. For each patient, images of the four quadrants of the uterus were digitized into a PC. The amniotic fluid portion in each ultrasonographic image was automatically detected, and its area was calculated. Its area was also manually determined by an expert physician (R. T.). The areas automatically detected by the algorithm were highly correlated with the areas manually delimited by the expert: r2 = 0.9722 (p < 0.01). The areas calculated by the program provide a good measure for the areas determined by the expert and may, therefore, be used for calculating the actual amniotic fluid volume.

Insights into the pathogenesis and natural history of fetuses with multicystic dysplastic kidney disease

To better delineate the natural history of multicystic displastic kidney disease (MCDKD) and provide insights into the pathogenesis of this condition, we report our experience in 102 prenatally detected cases. MCDKD is most commonly an incidental finding on prenatal ultrasound examination. The abnormality may be unilateral (76 per cent) or bilateral (24 per cent). In unilateral cases, abnormality of the contralateral kidney is common (33 per cent). Associated non-renal abnormalities occur frequently with both unilateral (26 per cent) and bilateral (67 per cent) MCDKD, and increase the risk for an abnormal chromosome study. Males are more likely to be affected than females with a ratio of 2.4:1, but females are twice as likely to have bilateral MCDKD and associated non-renal abnormalities, and four times more likely to have an abnormal chromosome study. We suggest that the option of chromosomal analysis should be discussed with all patients diagnosed with MCDKD in their fetus, if there is bilateral renal involvement or if an associated non-renal abnormality is present. Unilateral MCDKD without associated renal or non-renal abnormalities was not associated with an abnormal chromosome study, and resulted in favourable outcomes. While unilateral MCDKD, lack of associated anomalies, normal chromosome study and adequate amniotic fluid are all reassuring findings, a complete neonatal urologic work-up should be performed in all newborns. We believe the evaluation should include voiding cystourethrography to rule out vesicoureteral reflux. Our findings allow more precise counselling of patients regarding prognosis, and subsequent management of the fetus found to have MCDKD.

Ultrasound and fetal diagnosis of perinatal infection

Prenatal ultrasound can aid the clinician in evaluation of the patient with a suspected in utero TORCH infection, particularly toxoplasmosis, syphilis, and CMV. Demonstration of characteristic ultrasound findings in the high risk patient has a high predictive value for fetal infection and also may have prognostic significance. The sonologist should understand the limitations of ultrasound, discuss them with the patient, and document the discussion in the medical record. Patients should be counseled that ultrasound is not a sensitive test for fetal infection and that a normal fetal anatomy survey cannot predict a favorable outcome. In the low-risk patient, fetal infection should be considered when multiple organ system anomalies, fetal growth restriction, placental enlargement, or abnormalities of amniotic fluid volume are demonstrated.

The fetal outcome in pregnancies with isolated reduced amniotic fluid volume in the third trimester

Our aim was to assess the outcome of pregnancies where oligohydramnios, defined by a published gestational reference range for amniotic fluid index, was the only abnormal finding at third trimester scan, and all other ultrasound parameters including biometry were within normal limits at initial scan. A retrospective case-control study was performed at The Liverpool Maternity Hospital. 103 pregnancies with reduced amniotic fluid index in the third trimester and apparently normal fetal growth profile ultrasonographically were identified from ultrasound reports throughout 1993. Pregnancies in the third trimester with normal amniotic fluid index on index scan were also identified from these reports and 103 were matched for parity, gestational age at delivery, mode of onset of labour, presentation at labour and medical conditions. Exclusion criteria were ruptured membranes, fetal abnormalities, estimated fetal weight below the fifth centile at index scan and multiple pregnancies. The outcome criteria were birthweight, Apgar scores at delivery, induction and emergency delivery for fetal reasons and admission to Neonatal Intensive Care Unit. Statistical analysis was performed by Fisher's exact test and Gart's odds ratio. Compared with controls, pregnancies in the reduced liquor group had a higher number of babies below the 5th centile (odds ratio 5.2, 95% confidence interval 1.6 to 22), a higher risk of induction for fetal reasons (odds ratio 34.4, 95% confidence interval 5.35 to 1425.5) and admission to Neonatal Intensive Care Unit (odds ratio 9.77, 95% confidence interval 1.3 to 432). Any observed difference in the need for emergency delivery due to fetal reasons was not clinically significant (odds ratio 2.16, 95% confidence interval 0.77 to 6.6) The definition used for oligohydramnios used in this study appears to identify a group of babies with a fourfold risk of low birthweight and a high risk of admission to the Neonatal Intensive Care Unit and induction of labour for fetal reasons. This would suggest that pregnancies with isolated oligohydramnios require some form of fetal monitoring and further prospective studies are required to determine the most appropriate method.

Prevalence of polyhydramnios in the third trimester in a population screened by first and second trimester ultrasonography

AIMS

To determine the prevalence of polyhydramnios in a routine antenatal population, in which first and second trimester ultrasound screening for fetal abnormality had been performed and to examine the outcome in these pregnancies.

METHODS

A retrospective analytical survey of all obstetric ultrasound examinations performed in a university teaching hospital over a thirty-six month period. Polyhydramnios was defined as either the measurement of a single deepest pool of liquor > 8 cm (AFV) or according to the amniotic fluid index, the sum of a four quadrant measurement > 24 cm (AFI). Using the stated definitions, polyhydramnios was diagnosed in 37 women, 16 of whom had a raised AFI. The main outcomes of interest included the mode of onset of labour and mode of delivery (rates of spontaneous and induced labour, cesarean section deliveries), birth weight, presence or absence of fetal anomalies, and the perinatal outcome.

RESULTS

The prevalence of polyhydramnios in this study is lower (0.15% AFI > 24 cm and 0.36% AFV > 8 cm) than in previous studies. The association between polyhydramnios, maternal diabetes mellitus (10.8%), fetal abnormalities (5.4%) and fetal macrosomia (10.8%) was also lower than in past reports. There was a better overall fetal outcome compared with previous studies and no perinatal deaths were seen.

CONCLUSIONS

In this study, the prevalence of polyhydramnios in the third trimester was lower than in previous studies, as well as being associated with a better prognosis. This may have been the result of a combination of several factors. These include the introduction of multi-level ultrasound screening for fetal abnormality, and the improved care of diabetic women, and mothers with rhesus iso-immunisation.

Amnioinfusion in term labor with low amniotic fluid due to rupture of membranes: a new indication

OBJECTIVE

The null hypothesis was that the use of intrapartum amnioinfusion to induce term labor because of premature rupture of membranes when labor was complicated by low amniotic fluid volume due to vaginal loss would not improve fetal heart rate patterns, decrease the incidence of operative delivery, or improve neonatal acid-base status.

STUDY DESIGN

200 term pregnancies with low amniotic fluid due to vaginal loss were randomly chosen to receive intrapartum amnioinfusion or standard obstetric care without amnioinfusion. Fetal heart rate pattern, method of delivery and neonatal acid-base status were compared with Student's t test, chi-squared analysis, Mann-Whitney U- or Fisher's exact test.

RESULTS

When amnioinfusion was used, the fetuses had lower rates of variable (74 vs. 91%, P<0.01) or late (26 vs. 58%, P<0.001) decelerations. Spontaneous deliveries were more frequent (77 vs. 59%, P<0.01) and cesarean sections less frequent (3 vs. 10%, P<0.05). Mean umbilical arterial (7.24+/-0.07 vs. 7.21+/-0.08, P<0.01) and venous (7.31+/-0.06 vs. 7.28+/-0.08, P<0.01) pH were significantly higher in newborns with amnioinfusion, and babies in this group had lower rates of neonatal acidemia of arterial (22 vs. 36%, P<0.005) or venous (13 vs. 26%, P<0.005) origin.

CONCLUSIONS

Amnioinfusion improved fetal heart rate pattern, lowered the incidence of operative delivery, and improved neonatal acid-base status in term labor complicated by low amniotic fluid due to vaginal loss.

Utilizing sonography to follow fetal growth

In utero diagnosis of fetal growth abnormalities continues to pose a clinical dilemma. Although significant advances have been made in the understanding of growth disturbances and their clinical importance, false-positive and false-negative diagnoses of IUGR and excessive fetal growth continue to affect the accuracy of antenatal diagnosis. Until more accurate methods are developed to aid in diagnosis, multiple biometric parameters should be assessed in patients either at risk for or with a suspected growth disturbance. Serial measurements obtained every 2 to 3 weeks may enhance diagnostic capabilities. Although antenatal diagnosis of IUGR has been shown to be of benefit in improving outcome, more study is needed to determine whether there is a benefit in antenatal diagnosis of macrosomia or LGA.

Clinical utility of amniotic fluid volume assessment

Abnormal amniotic fluid volume is associated with increased maternal risk and perinatal morbidity and mortality. Until the advent of ultrasonography, the invasive nature of amniotic fluid volume assessment limited its clinical utility. Refinements in quantifying the noninvasive sonographic assessment of oligohydramnios and hydramnios have improved the ability of clinicians to identify at-risk pregnancies. This article reviews the available methods of amniotic fluid volume assessment and outlines a comprehensive approach to sonographic screening and monitoring.

Amniotic fluid and the umbilical cord: the fetal milieu and lifeline

Amniotic fluid volume should be routinely assessed in every second and third trimester case. A review of amniotic fluid physiology and techniques for ultrasound evaluation of fluid volume is presented. The causes and significance of oligohydramnios and polyhydramnios are stressed. Umbilical cord abnormalities are often incidently observed at the time of amniotic fluid evaluation. The clinical significance of some common umbilical cord abnormalities such as a two-vessel cord and nuchal cord are discussed. Other, more uncommon entities such as cord mass lesions are also reviewed. Finally, the role of cord Doppler interrogation in determining fetal well-being is discussed.

Umbilical arterial flow change during hemodialysis

A pregnant woman was performed hemodialysis 3 times a week from early gestation. At 30 weeks of gestation, fetal growth and amniotic fluid volume were normal. We performed 3-hour hemodialysis 6 times a week. Cesarean section was performed at 38 weeks of gestation, she delivered a healthy neonate weighing 2575 g. During hemodialysis, we performed Doppler flow velocimetry on the umbilical artery. The resistance index revealed a remarkable decrease after 1.5 hour hemodialysis. But it recovered 3 hours of administration as well as after completion of treatment. We speculated this change in the resistance index of the umbilical artery was caused by transient maternal hypovolemia.

Amnioinfusion in labor induction of term pregnancies with premature rupture of the membranes and low amniotic fluid

OBJECTIVE

To analyze the utility of prophylactic amnioinfusion in term pregnancies with PROM and a low amniotic fluid index during labor induction.

METHOD

Forty-two women with amnioinfusion and 42 in a control group with amniotic fluid index (AFI) below 10 cm when admitted to labor induction were studied. All patients had electronic fetal heart rate and intrauterine pressure continuous monitoring. Amnioinfusion of normal saline (37 degrees C) was realized in the study group, using a continuous perfusion pump at 600 ml/h for 1 h, after which the AFI was again recorded; if this was < 15, the perfusion was continued at 180 ml/h until full cervical dilatation was achieved or until uterine baseline activity reached 20 mm Hg. The control group received identical obstetric care except in respect of amnioinfusion.

RESULT

Both groups were similar in age, primiparity, gestational age, initial AFI, interval from rupture of membranes until delivery and length of labor. The amnioinfusion of 600 ml in 1 h significantly increased the AFI (an increase of 7.2 +/- 3.9 vs. a decrease of 1.1 +/- 1.6, P < 0.01). In the amnioinfusion group, there was a significantly lower rate of cesarean deliveries (0 vs. 6, P < 0.05) and a better mean umbilical arterial pH at delivery (7.24 +/- 0.07 vs. 7.21 +/- 0.08, P < 0.05). No differences were observed in maternal or neonatal hospitalization days or infectious morbidity.

CONCLUSION

It is concluded that prophylactic amnioinfusion improves neonatal metabolic state when used in labor induction of term pregnancies with PROM and a low amniotic fluid index.

Intra- and early postpartum ultrasonography: a review. Part I

The objective of this article is to review current literature pertaining to intra- and early postpartum sonography. All the manuscripts published in the English language regarding this topic were selected from a MEDLINE search from 1966 through August 1997. Additional sources were identified through cross-referencing. Currently, intra- and early postpartum sonography may be performed for either maternal or fetal indications. Maternal indications include cervical assessment in preterm labor/rupture of membranes, assessment of the lower uterine segment, size and position of uterine fibroids, guided-placement of central venous or pulmonary artery catheters, detection of intraoperative venous air embolism, deep venous thrombosis, assist management of the third-stage of labor, postpartum hemorrhage or febrile morbidity. Fetal indications include an anatomical survey in patients presenting without prenatal care, verification of fetal presentation, estimated fetal weight, assessment of the breech-presenting fetus, external cephalic version, management of delivery of the second-twin, and internal podalic version. Doppler flow velocimetry is a useful tool in depicting both maternal and fetal intrapartum physiologic changes. We conclude that intra- and early postpartum sonography is an established versatile diagnostic and interventional-guiding modality for many obstetric conditions and should be readily available on labor and delivery suites.

Necrotizing funisitis: clinical significance and association with chronic lung disease in premature infants

OBJECTIVES

Our purpose was to analyze the clinical significance of necrotizing funisitis, an unusual type of chronic inflammation of the umbilical cord, and to determine whether necrotizing funisitis is associated with chronic lung disease in premature infants.

STUDY DESIGN

A total of 52 perinatal factors were prospectively assessed in 18 pregnant women and their fetuses in cases of chorioamnionitis at delivery occurring at 22 to 30 gestational weeks; a statistical comparison between the necrotizing funisitis group (n = 5) and the group without necrotizing funisitis (n = 18) was carried out.

RESULTS

Significant correlations were found between necrotizing funisitis and the following factors: maternal serum C-reactive protein level on admission (p = 0.014), fetal distress (p = 0.044), umbilical artery blood pH value (p = 0.037) and polynuclear neutrophilic leukocyte count at birth (p = 0.014), chronic lung disease (p = 0.035), need for dexamethasone therapy for chronic lung disease (p = 0.029), duration of oxygen supplementation (p = 0.026), and length of hospital stay (p = 0.026).

CONCLUSIONS

There was a significant association between necrotizing funisitis and development of chronic lung disease, suggesting that necrotizing funisitis is an important risk factor for the development of chronic lung disease.

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

Intrapartum oligohydramnios does not predict adverse peripartum outcome among high-risk parturients

OBJECTIVE

Oligohydramnios can be defined by an amniotic fluid index < 5th percentile for gestational age or an amniotic fluid index < or = 5.0 cm regardless of gestational age. The purpose of this prospective study was to determine whether oligohydramnios by either definition predicts accurately, in a high-risk population, the risks for cesarean section for fetal distress, Apgar score < 7 at 5 minutes, and neonatal acidosis.

STUDY DESIGN

An amniotic fluid index was obtained in 490 consecutive parturients with medical or obstetric complications and a reliable gestational age. After each delivery, an umbilical arterial blood gas analysis was obtained. Both measures of amniotic fluid index were rated as screening tests with use of sensitivity, specificity, predictive values, and receiver-operator characteristic curves.

RESULTS

The incidences of cesarean section for fetal distress and umbilical arterial pH < 7.00 were 14% and 1.8%, respectively. The 70 neonates delivered by cesarean section for distress, compared with the 420 without, had a significantly higher incidence of pH < 7.00 (8.5% vs 0.7%, p = 0.0004, relative risk 5.0, 95% confidence interval 2.9 to 8.4). Sensitivity and positive predictive values of an amniotic fluid index < 5th percentile for gestational age to predict pH < 7.00 were 0.8% and 22%, respectively, and for an amniotic fluid index < or = 5.0 cm, 0.5% and 11%, respectively. Receiver-operator characteristic curves indicate that an amniotic fluid index between 0 and 20 cm cannot predict accurately which parturients will have cesarean sections for distress or be delivered of a newborn with a low Apgar score at 5 minutes or a pH < 7.10.

CONCLUSION

Both criteria for oligohydramnios are poor predictors of adverse outcome for high-risk intrapartum patients.

Clinical assessment of amniotic fluid

Amniotic fluid volume estimation has become an integral part of fetal evaluation. Although the sonographic techniques clinically available are limited in their accuracy and predictive value, the careful performance of AFI measurements provide important and complementary clinical data on which to base management decisions in pregnancies at risk.

The accuracy of ultrasound evaluation of amniotic fluid volume in singleton pregnancies: the effect of operator experience and ultrasound interpretative technique

The objective of this study was to evaluate the effect of operator experience and ultrasound interpretation technique on the accuracy of ultrasound estimates of amniotic fluid volume. Ultrasound evaluation was carried out by an obstetric resident, a nurse sonographer, a maternal-fetal medicine fellow, and a maternal-fetal medicine staff member to subjectively estimate (visual interpretation without sonographic measurements) amniotic fluid volume in 63 pregnancies. Amniotic fluid volume was also evaluated using ultrasound measurements based on the largest vertical pocket technique, the amniotic fluid index, and the two-diameter pocket method. The accuracy of these ultrasound estimates was assessed by comparing the ultrasound results to actual amniotic fluid volume as determined by a dye-dilution technique. For analysis, amniotic fluid volumes were classified as oligohydramnios, normal, or hydramnios using established volumetric criteria for singleton pregnancies. Subjective estimates ranged from 65% to 70% correct and did not differ by operator experience except for the more accurate diagnosis of hydramnios by the maternal-fetal medicine staff. The three sonographic measurements were similar in overall accuracy (59-67%). The two-diameter pocket method was, however, significantly more accurate in identifying oligohydramnios. It appears that neither operator experience nor sonographic technique greatly affects the accuracy of ultrasound estimates of amniotic fluid volume.

Physiology of amniotic fluid volume regulation

Although there are fairly wide variations AFV normally undergoes characteristic changes across gestation in which it increases from 10-20 ml at 10 weeks gestation to average 800 ml at 24 weeks. Little change occurs from then until near term when AFV begins to decrease, and large decreases can occur in postterm pregnancies. Across gestation, 95% of AFVs are within the range of 1/2.57-2.57 times the gestational mean volume and 99% are within the range of 1/3.40-3.40 times the gestational mean. Although there are six pathways in which fluid and solutes can enter and/or leave the amniotic sac, there are only four primary pathways that contribute to AFV during late gestation. These include fetal urine and lung fluid secretion as the two primary sources of fluid, with fetal swallowing and intramembranous absorption as the two primary routes of amniotic water clearance. The intramembranous pathway also appears to be a primary source of amniotic solutes (e.g., sodium and chloride). Although fetal hypoxia has been widely believed to cause oligohydramnios, fetal hypoxic hypoxia and anemic hypoxia both appear to be associated with an increased AFV and polyhydramnios rather than oligohydramnios. It is speculated that the oligohydramnios associated with fetal hypoxia is caused by placental dysfunction in addition to the hypoxia.

Effect of fetal movement on the amniotic fluid index in diamniotic twin gestations

Fetal movement changes the size and location of amniotic fluid pockets during measurement of the amniotic fluid index. In singleton gestations, the effect of redistributing the fixed intrauterine fluid volume on the amniotic fluid index is clinically insignificant. In this study, we tested the hypothesis that the index in twin pregnancies is unaffected by fetal movement. A single examiner prospectively determined the amniotic fluid index before and after three discrete episodes of movement by both fetuses of 82 diamniotic twin pregnancies referred for obstetric sonograms between 20 and 38 weeks' menstrual age. A reliable blinded examiner provided a second post-movement measurement as a control. Data were analyzed by the paired t-test. The mean change in the amniotic fluid index after fetal movement was 2.1 +/- 0.2 cm and 3.7 +/- 0.3 cm for post-movement determinations by the same and blinded examiners, respectively (p < .001). Interobserver variation was 3.5 cm. Intraobserver variation was 1.8 cm for the first examiner and 2.2 cm for the second examiner. Therefore, interobserver and intraobserver variation can account for the observed change in the amniotic fluid index following movement of both diamniotic twins.

Transdermal nicotine replacement in pregnancy: maternal pharmacokinetics and fetal effects

OBJECTIVE

Our purpose was to measure any short-term effects that the transdermal nicotine replacement system may have in pregnancy and to verify salivary nicotine and cotinine levels during patch placement.

STUDY DESIGN

After customary smoking cessation efforts had failed, six prenatal patients between 28 and 37 weeks' gestation who smoked between one and two packs per day were enrolled in this prospective study. The patients were admitted to the General Clinical Research Center for a period of 21 hours. During hospitalization we performed maternal and fetal assessments including vital signs, biophysical profile and electronic fetal monitoring, amniotic fluid index, and umbilical artery Doppler examinations. Salivary samples for cotinine and nicotine levels were collected at standard intervals.

RESULTS

There were no measurable differences in fetal or maternal well-being. During patch use salivary nicotine levels increased as expected, to a mean value of 19.0 +/- 13.5 micrograms/L at 480 minutes. Salivary cotinine concentrations remained low (approximately 50 micrograms/L) and varied little during the 480-minute period that the patch was worn. Overall, patients were satisfied with the transdermal patches.

CONCLUSION

There were no adverse maternal or fetal effects from the transdermal nicotine replacement system over the 6-hour period. Salivary nicotine concentrations were consistent with those seen in nonpregnant adults. Surprisingly, salivary cotinine concentrations were much lower than those seen in smoking nonpregnant adults.

A randomised comparison between amniotic fluid index and maximum pool depth in the monitoring of post-term pregnancy

OBJECTIVE

To compare the impact of two different ultrasound methods for assessing amniotic fluid volume on the incidence of obstetric interventions in post-term pregnancies.

DESIGN

A prospective randomised controlled trial.

SETTING

Liverpool Women's Hospital.

PARTICIPANTS

Five hundred women with singleton, uncomplicated pregnancies with gestational age > or = 290 days.

INTERVENTIONS

Random allocation to fetal monitoring by either: 1. amniotic fluid index and computerised cardiotocography, or 2. maximum pool depth and computerised cardiotocography.

MAIN OUTCOME MEASURES

Primary: caesarean section. Secondary: the number of abnormal monitoring tests, induction of labour, intrapartum management and neonatal outcome.

RESULTS

The number of abnormal amniotic fluid indices was significantly higher than the number of abnormal maximum pool depths (10% vs 2.4%; OR 4.51, 95% CI 1.82-11.21; P = 0.0008) which resulted in more inductions for abnormal post-term monitoring in the amniotic fluid index group (14.8% vs 8.4%; OR 1.89; 95% CI 1.07-3.33; P = 0.0362) and more intrapartum electronic fetal monitoring (94.4% vs 88.4%; OR 2.21; 95% CI 1.13-4.29; P = 0.0255). There were no other statistically significant differences in outcomes related to labour and delivery, but there was a trend towards more caesarean sections in the amniotic fluid index group (18.8% vs 13.2%), in particular caesarean sections for fetal distress (8% vs 4%). There were no perinatal deaths and no statistically significant differences in perinatal outcome between the two groups.

CONCLUSIONS

Published reference ranges for amniotic fluid index overestimate the number of abnormal results in post-term pregnancies. Their use, when compared with maximum pool depth, is likely to increase the number of obstetric interventions with, as yet, an uncertain impact on perinatal mortality and morbidity. It is possible that antepartum fetal assessment in pregnancies where the risk of adverse perinatal outcome is very low may cause, rather than prevent morbidity.

Anthropometric characteristics of full-term infants: effects of varying degrees of "normal" glucose metabolism

Aim of this study was to examine the maternal-neonatal outcome and the neonatal anthropometric characteristics of a full-term mother-infant pairs group with a positive oral glucose challenge test (GCT) without gestational diabetes mellitus (GDM). Our study involved 1615 white women with singleton pregnancies who underwent universal screening for GDM in two periods of pregnancy. This population was divided into three groups according to GCT results: 1) 172 patients with abnormal GCT in both periods; 2) 391 patient with normal GCT in the early period and abnormal GCT in the late period; 3) 1052 patients with normal GCT in both periods (control group). The incidence of LGA (large for gestational age) infants was higher in Group (40.7%) and Group 2 (22.0%) respect to control group (8.3%) (p < 0.00001 and p < 0.0001 respectively) and was significantly different in the two groups (p < 0.0008). Comparison among the three groups of LGA infants showed the following results: male and female newborns of Group I were heavier than those of Group 2 and of the control group, while males and females of the control group had significantly greater length and cranial circumference means. A significant decrease in ponderal index, choracic circumference, weight/length ratio means could be seen as well as a significative increase in cranial/thoracic circumference ratio means from Group I to the control group. These data confirm the involvement of fetal development in terms of weight and anthropometric characteristics in the presence of alterations in maternal glucose metabolism which are not currently classified as gestational diabetes.

Serial amniotic fluid index in severe preeclampsia: a poor predictor of adverse outcome

OBJECTIVE

The purpose of the study was to determine the relationship between low amniotic fluid index and intrauterine growth restriction and nonreassuring fetal testing in patients with severe preeclampsia.

STUDY DESIGN

We reviewed the medical records of 136 women with severe preeclampsia managed conservatively for at least 48 hours. Patients were followed up with a daily nonstress test and amniotic fluid index. We evaluated amniotic fluid index < or = 5 cm and < or = 7 cm, measured on admission or just before delivery (i.e., final), and attempted to correlate these findings with the incidence of nonreassuring fetal testing necessitating cesarean section or the incidence of intrauterine growth restriction (birth weight < or = 10th percentile).

RESULTS

One hundred seven patients had a cesarean section, but only 42 (39%) of these were for a nonreassuring fetal heart rate tracing or a persistent biophysical profile of < or = 4, and 38 (36%) of the pregnancies resulted in infants with intrauterine growth restriction. During expectant management, the amniotic fluid index worsened for 61 (45%) patients and improved or remained the same for 75 (55%). For those with an amniotic fluid index of < or = 5 cm both on admission and at delivery, there was a significantly higher incidence of intrauterine growth restriction compared with those with an amniotic fluid index > 5 cm (p = 0.007 and p = 0.029, respectively). However, there was no association between intrauterine growth restriction and an amniotic fluid index < or = 7 cm. Moreover, there was no difference in the frequency of nonreassuring fetal heart rate testing on the basis of amniotic fluid volume (p = 0.59) or intrauterine growth restriction (p = 0.4).

CONCLUSIONS

For women with severe preeclampsia remote from term, an amniotic fluid index < or = 5 cm is predictive of intrauterine growth restriction but lacks sensitivity. There is no association between the amniotic fluid index status and frequency of cesarean section for fetal distress or nonreassuring fetal testing.

Fetal ultrasonography: normal biometric ranges in the baboon (Papio hamadryas)

Normal biometric ranges for fetal growth in a captive breeding baboon (Papio hamadryas) colony are described. Measurements include crownrump length, biparietal diameter, binocular distance, head circumference, abdominal circumference, femur length and amniotic fluid index. The pattern of fetal growth is compared with other baboon subspecies and man. The uses and limitations of such data for breeding colony management and optimum utilisation of experimentally derived data are discussed.

Transabdominal amnioinfusion in oligohydramnios at term before induction of labor with intact membranes: a randomized clinical trial

OBJECTIVE

Our purpose was to determine the effectiveness of transabdominal amnioinfusion before induction of labor in reducing the incidence of fetal distress in pregnancies with oligohydramnios at term.

STUDY DESIGN

Between June 1991 and September 1994 primiparous women with ultrasonographic evidence of oligohydramnios at term, intact membranes, and unripe cervix (Bishop score < or = 6), candidates for induction of labor with cervical or vaginal prostaglandin E2 gel, were randomly selected to receive transabdominal amnioinfusion (amnioinfused group, n = 39) or to proceed with direct labor induction (control group, n = 40). Inclusion criteria were (1) singleton gestation, (2) vertex presentation, (3) ultrasonographic estimation of fetal weight > or = 2500 gm, and (4) reactive nonstress test. Fetoneonatal outcome variables were compared between the two groups. Statistical analysis used contingency tables, Student t test, or Wilcoxon rank-sum tests, where applicable.

RESULTS

Amnioinfusion was successfully performed in 100% of the patients randomized for the procedure. The incidence of severely abnormal fetal heart rate tracings was significantly higher in the control than in the amnioinfused group (42% [17/33] vs 5% [2/37], relative risk 12.9, 95% confidence interval 2.4 to 56.4). The rate of cesarean sections performed for fetal distress was fivefold higher in the control group (25% [10/40] vs 5% [2/39], relative risk 4.9, 95% confidence interval 1.1 to 32.4). No bleeding complications or fetomaternal infectious morbidity were noticed.

CONCLUSION

Transabdominal amnioinfusion is a safe, effective option for the prevention of fetal distress in pregnancies with oligohydramnios at term with intact membranes and unripe cervix.

Ultrasonographic measurement of amniotic fluid volume in normal diamniotic twin pregnancies

OBJECTIVE

Our purpose was to determine the amniotic fluid volume in normal diamniotic twins.

STUDY DESIGN

The single amniotic fluid index for both twin members, the maximum depth and width of each twin's largest pocket, were measured every 4 to 6 weeks between 15 and 40 weeks in 91 normal diamniotic twin gestations. The two-diameter pocket in each twin was determined as its largest pocket's depth multiplied by its width. Normal twin gestations were defined as those with <20% birth weight discordance, appropriate for gestational age, no fetal anomalies, delivery at > or = 37 weeks, and normal newborns. Amniotic fluid index values, depths, and two-diameter pockets were stratified into 2-week intervals and transformed into base 10 logarithms because of their nongaussian distributions. The correlations of these measurement with gestational age were evaluated. Their means and 90%, 95%, and 98% confidence intervals were determined.

RESULTS

The amniotic fluid index changed significantly with gestational age. However, depths and two-diameter pockets did not. The amniotic fluid index rose from 15 to 24 weeks, plateaued until 36 weeks, and then declined. The 90%, 95%, and 98% confidence intervals for each twin's depth were 2.4 to 7.9, 2.1 to 8.8, and 1.9 to 10 cm, respectively (mean 4.3 cm). These respective confidence intervals for each twin's two-diameter pocket were 8 to 44, 7 to 52, and 5 to 63 cm2 (mean 19 cm2). The amniotic fluid index confidence interval curves were plotted from the log (amniotic fluid index)=0.8276 + 0.01675x-0.0000001900x4, R2=0.78, p=0.002 (where x is gestational age).

CONCLUSION

The amniotic fluid volume in normal diamniotic twin pregnancies was established ultrasonographically. Only the amniotic fluid index changed significantly with gestational age. These findings may have significance in the clinical management of twin gestation.

Accuracy of prenatal diagnosis of renal agenesis with color flow imaging in severe second-trimester oligohydramnios

OBJECTIVE

Our purpose was to examine the potential of color flow imaging to assess the presence of renal arteries in second-trimester pregnancies complicated by severe oligohydramnios.

STUDY DESIGN

Thirty-three consecutive second-trimester pregnancies referred with severe oligohydramnios were prospectively studied with high-resolution color Doppler ultrasonography to establish the presence or absence of renal arteries. Prenatal findings were correlated with the presence or absence of fetal kidneys at postmortem or postnatal examination.

RESULTS

Neither renal artery was visualized in eight fetuses; postmortem examination confirmed bilateral renal agenesis in seven and unilateral renal agenesis with a contralateral atrophic multicystic kidney in the other. Only one renal artery was seen in three; postmortem examination demonstrated unilateral renal agenesis in two fetuses and bilateral multicystic dysplastic kidneys in the other. Postmortem or postnatal evaluation confirmed the presence of both kidneys in all 22 fetuses in which both renal arteries were identified prenatally.

CONCLUSIONS

Color Doppler ultrasonography is useful in the prenatal evaluation of fetuses with severe second-trimester oligohydramnios to demonstrate the presence or absence of renal arteries. This technique should be added to the armamentarium of prenatal tests to evaluate second-trimester fetuses with severe oligohydramnios.

Nonimmune fetal hydrops: diagnosis and obstetrical management

As the incidence of Rh-isoimmunization has been decreasing with the availability of Rh immune globulin, the proportion of cases of fetal hydrops from nonimmune causes has increased. Evaluation of the fetus with hydrops requires an integrated approach, beginning with targeted ultrasound evaluation and potentially including maternal and fetal blood testing and other invasive testing. Because the list of conditions that may cause hydrops is long and continues to grow, it is often difficult to make a precise diagnosis; however, through a systematic approach, one may frequently narrow the etiology to a category of disorders and determine whether any interventions are available that are likely to be helpful in improving the outlook for the fetus.

Is polyhydramnios in an ultrasonographically normal fetus an indication for genetic evaluation?

OBJECTIVE

Our purpose was to determine the frequency of fetal chromosomal anomalies in pregnancies complicated by polyhydramnios.

STUDY DESIGN

Between Jan. 1, 1992, and July 31, 1993, an amniotic fluid index was measured prospectively in 2730 third-trimester pregnant women. Polyhydramnios was defined as an amniotic fluid index > or = 24 cm. A computer search identified all infants born with structural or chromosomal anomalies.

RESULTS

Polyhydramnios was detected in 49 of 2730 women (1.7%). The incidence of chromosomal anomalies was two in 49 (4.1%) compared with three in 2681 (0.12%) among women with normal fluid (p < 0.05). Six of the 49 newborns had structural anomalies (12.2%), whereas 48 of 2681 (1.8%) structural anomalies occurred in the control group (p < 0.05). Among study patients both fetuses with chromosomal anomalies were growth retarded; four of the six structural anomalies were associated with an amniotic fluid index > 30 cm.

CONCLUSIONS

(1) Polyhydramnios is associated with an increased incidence of congenital fetal anomalies. (2) Growth-retarded fetuses with polyhydramnios warrant genetic evaluation. (3) A genetic study is not absolutely indicated for patients with polyhydramnios and a sonographically normal fetus.

Acute maternal hydration in third-trimester oligohydramnios: effects on amniotic fluid volume, uteroplacental perfusion, and fetal blood flow and urine output

OBJECTIVE

Our purpose was to determine whether acute maternal hydration in pregnancies with third-trimester oligohydramnios (1) increases amniotic fluid index and hourly fetal urine production rate and (2) alters uteroplacental perfusion and fetal blood flow.

STUDY DESIGN

Ten women with third-trimester oligohydramnios (amniotic fluid index < or = 5 cm) and 10 controls with normal amniotic fluid volume (amniotic fluid index > 7 cm) were prospectively recruited for this study. Maternal plasma and urine osmolality, amniotic fluid index, hourly fetal urine production rate, and Doppler flow velocimetry of maternal uterine artery and fetal umbilical, descending aorta, middle cerebral, and renal arteries were determined before and after oral hydration by having the patient drink 2 L of water over 2 hours.

RESULTS

There was a significant reduction in maternal plasma (p < 0.05) and urine osmolality (p < 0.0001) in both groups after short-term oral hydration. Hydration increased amniotic fluid volume in women with oligohydramnios (mean change in amniotic fluid index 3.2 cm, 95% confidence intervals 1.1 to 5.3; p < 0.02) but not in those with normal amniotic fluid volume (mean change in amniotic fluid index -2.0, 95% confidence intervals -4.1 to +0.2). The hourly fetal urine production rate, however, did not increase in either group (mean change in hourly fetal urine production rate 3.5 ml/hr, 95% confidence intervals -11.7 to +18.7 and -6.8 ml/hr, 95% confidence intervals -2.9 to -10.7, respectively). Hydration was associated with an increase in uterine artery mean velocity in the oligohydramnios group (mean change in mean velocity 16.7 cm/sec, 95% confidence intervals 8.0 to 25.3; p < 0.006) but not in controls (mean change in mean velocity 1.2 cm/sec, 95% confidence intervals -19.7 to +22.1). There was no change in pulsatility index or in velocity in any of the fetal vessels studied in either group.

CONCLUSIONS

Short-term maternal oral hydration increases the amniotic fluid index in women with third-trimester oligohydramnios. Although the mechanism for this effect remains unclear, it could not be accounted for by fetal urination in this study but instead was associated with improved uteroplacental perfusion.

Prenatal findings in generalized amyoplasia

Amyoplasia is a rare, sporadic condition characterized by different degrees of maldevelopment of the skeletal muscles, which are replaced by fibrous and fatty tissue. In this report, we present a case of generalized amyoplasia presenting at 19 weeks' gestation. The most striking finding was the absence of fetal movements, resulting in severe multiple congenital contractures, hydrops, and polyhydramnios. At autopsy, histological examination of the skeletal muscle showed small groups of poorly developed fibres within areas of fat. This report suggests that generalized amyoplasia could be a common cause of severe forms of multiple congenital contractures, but is probably underdiagnosed at post-mortem because of inadequate examination of muscles. Definitive diagnosis is important in determining the risks of recurrence in these cases.

The impact of amniotic fluid volume assessed intrapartum on perinatal outcome

OBJECTIVE

Our purpose was to determine the value of routine intrapartum amniotic fluid volume assessment on perinatal outcome.

STUDY DESIGN

Patients admitted for labor and delivery who were ultimately delivered between January 1988 and June 1989 with a gestational age > or = 26 weeks and who had an intrapartum amniotic fluid index composed the study group. The amniotic fluid index was determined by the four-quadrant technique on admission to labor and delivery. Oligohydramnios was defined as an amniotic fluid index < or = 5 cm (n = 170), borderline oligohydramnios as an amniotic fluid index 5.1 to 8.0 cm (n = 261), and normal amniotic fluid volume as an amniotic fluid index 8.1 to 20 cm (n = 336). Nine patients with an amniotic fluid index > 20 cm were excluded from data analysis. The oligohydramnios and borderline oligohydramnios groups were compared with the normal group with regard to antenatal, intrapartum, and postpartum variables.

RESULTS

The groups had similar maternal age, parity, gestational age at delivery, and antenatal complications. Meconium-stained amniotic fluid occurred significantly less often in the oligohydramnios group compared with the normal group (relative risk 0.67, 95% confidence interval 0.49 to 0.92). However, variable decelerations occurred significantly more often in the oligohydramnios group compared with the normal group (relative risk 1.44, 95% confidence interval 1.12 to 1.87), and cesarean delivery for fetal distress also occurred significantly more often (relative risk 6.83, 95% confidence interval 1.55 to 30.4). There was no difference in Apgar scores or neonatal complications between groups. The efficacy of intrapartum-determined oligohydramnios predicting cesarean delivery for fetal distress gave a sensitivity of 78%, a specificity of 74%, a positive predictive value of 33%, and a negative predictive value of 95%.

CONCLUSION

The amniotic fluid index for detecting intrapartum oligohydramnios is a valuable screening test for subsequent fetal distress requiring cesarean delivery.

Assessment of fetal activity and amniotic fluid volume in the prediction of intrauterine infection in preterm prelabor amniorrhexis

OBJECTIVE

Our purpose was to assess fetal activity, fetal heart rate patterns, and amniotic fluid volume in the prediction of intrauterine infection in pregnancies complicated by preterm prelabor amniorrhexis.

STUDY DESIGN

A prospective study was performed on 89 patients with preterm prelabor amniorrhexis undergoing fetal blood and amniotic fluid sampling for microbiologic investigations. Within 2 hours before cordocentesis and amniocentesis, computerized fetal heart rate monitoring was carried out and ultrasonographic examination was performed for assessment of biophysical profile and amniotic fluid volume.

RESULTS

In the pregnancies with microbiologic evidence of intrauterine infection compared with those with no infection, there was a tendency for a lower biophysical profile score and amniotic fluid index and an increased fetal heart rate. However, in the majority of pregnancies with positive amniotic fluid or fetal blood cultures the results of the various tests were normal.

CONCLUSION

In pregnancies complicated by preterm prelabor amniorrhexis assessment of fetal activity and amniotic fluid volume do not provide useful prediction of intrauterine infection.

Twin-twin transfusion syndrome: intraamniotic pressure measurement in the assessment of volume reduction at serial amniocenteses

Two cases of severe twin-twin transfusion syndrome are described. In both, serial amniocenteses were followed by resolution of the disordered inter-twin haemodynamics with 4 intact term survivors. In all reports to date of aggressive reduction with or without successful outcome, volume reduction has been dictated by subjective or semiquantitative ultrasonic estimates of liquor volume. With the use of intraamniotic pressure estimation we describe a more rational basis for the removal of these large volumes of amniotic fluid.

The influence of operator transducer pressure on ultrasonographic measurements of amniotic fluid volume

OBJECTIVE

Our purpose was to study the effect of operator transducer pressure on amniotic fluid index and single deepest pool measurements and their intraobserver and interobserver variability.

STUDY DESIGN

Forty subjects in the third trimester with intact membranes were studied by two observers at three predetermined operator pressures. Pressure was measured by interfacing a flexible water-filled reservoir connected to a manometer between the maternal abdomen and the ultrasonography transducer. The amniotic fluid index and single deepest pool were measured on screen by another operator, and data were analyzed by calculating components of variance.

RESULTS

Compared with medium pressure, low pressure resulted in a 13% increase in amniotic fluid index (p < 0.001), and high pressure resulted in a 21% fall in amniotic fluid index (p < 0.001). The single deepest pool was less sensitive to pressure, with a 11% increase at low pressure (p < 0.001) and a 16% fall at high pressure (p < 0.001). Intraobserver error was 17% for amniotic fluid index and 18% for single deepest pool when operator pressure was controlled at medium pressure; this increased to 28% and 24%, respectively, when pressure was not controlled (p < 0.01). Interobserver error was consistently very low.

CONCLUSION

Both techniques are highly sensitive to the pressure applied to the maternal abdomen during scanning. The reproducibility of amniotic fluid index and single deepest pool is comparable. The use of the same observer for serial measurements of amniotic fluid index would appear to be less important than careful attention to transducer pressure.

Clinical and echographic features of in utero cardiac dysfunction in the recipient twin in twin-twin transfusion syndrome

OBJECTIVE

Fetal twin-twin transfusion syndrome (TTTS) presenting in the second trimester has been associated with almost no perinatal survival until recently, when serial drainage of amniotic fluid has improved the prognosis to 70%-80%. Most recipient twins now survive but develop cardiac dysfunction. The study was undertaken to evaluate the abnormal echocardiographic features and clinical complications of cardiac disease in the recipient twin of TTTS.

DESIGN

Antenatal and postnatal echocardiographic and clinical observational study.

SETTING

Antenatal studies in a tertiary referral centre. Postnatal management and follow up were performed by the same paediatric cardiologist, either at the obstetric hospital or at the regional referral centre.

PATIENTS

Twin pregnancies complicated by TTTS with severe polyhydramnios diagnosed earlier than 25 weeks that proceeded until viability (n = 5).

INTERVENTION

Serial fetal echocardiography with colour Doppler. Postnatal echocardiography in the first week and between two and seven months. Serial amnioreduction was performed in all pregnancies. Digoxin treatment, pericardiocentesis, paracentesis, or laser ablation of placental anastomoses was undertaken when there was hydrops.

RESULTS

Increased cardiothoracic ratio and tricuspid regurgitation were seen in all recipient twins. High pulmonary artery velocities developed in three. One recipient twin died a week after delivery of endocardial fibroelastosis and infundibular pulmonary stenosis. Two other had balloon dilatation for pulmonary stenosis, one shortly after birth and one at four months. A further twin has apical thickening of the right ventricle at six months. The remaining recipient twin had normal echocardiographic findings at follow up.

CONCLUSION

This report characterises for the first time a cardiac disease acquired in utero in the recipient twin in pregnancies complicated by TTTS. Clinical manifestations in utero range from mild to critical pulmonary stenosis or lethal cardiomyopathy. Although perinatal prognosis seems to be related to the severity of dysfunction when first diagnosed in utero, follow up in infancy is recommended in view of the possibility of progressive pulmonary stenosis.

Direct volume measurement at midtrimester amnioinfusion in relation to ultrasonographic indexes of amniotic fluid volume

OBJECTIVE

Our purpose was to investigate the relationship between amniotic fluid volume and semiquantitative ultrasonographic assessment of amniotic fluid in the midtrimester.

STUDY DESIGN

Sixteen pregnancies between 16 and 28 weeks with minimal amniotic fluid (severe oligohydramnios or anhydramnios) and intact membranes were studied at the time of clinically indicated amnioinfusion. The amniotic fluid index and deepest pool measurement were determined before and immediately after the procedure. Correlations were sought by means of standard regression techniques with amniotic fluid volume (i.e., volume infused) on the basis of the assumption that amniotic fluid volume before amnioinfusion was effectively nil.

RESULTS

There was a significant linear relationship between amniotic fluid index and volume infused (y = 7.336 + 0.015x; R2 = 0.30, p < 0.05). However, no correlation with the deepest pool measurement technique was found (R2 = 0.11, p > 0.05).

CONCLUSION

Amniotic fluid index is preferable to deepest pool measurement in assessing amniotic fluid volume in the second trimester of pregnancy. The low variance (30%) suggests that better predictors of amniotic fluid volume are still required.