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School of Women’s and Infants’ Health, The University of Western Australia, Perth, WA, AustraliaWomen and Infants Research Foundation, Perth, WA, Australia
The purpose of this study was to evaluate the contribution of amnioreduction to the management of singleton pregnancies that are complicated by symptomatic polyhydramnios.
Study Design
Retrospective review of all singleton pregnancies that received at least 1 amnioreduction for polyhydramnios from 2000-2012 at a single obstetric unit that provides a statewide service. The indications, procedural techniques, and pregnancy outcomes were evaluated.
Results
One hundred thirty-eight women with polyhydramnios (maximal vertical pocket [MVP], ≥8 cm) had 271 amnioreduction procedures during the study period. The median gestation at the first drain was 31.4 weeks (interquartile range, 28.4–34 weeks) and a median of 1 procedure (interquartile range, 1–2 procedures) was performed per pregnancy. Sixty-three women (45.6%) required >1 amnioreduction. The median volume removed per pregnancy was 2100 mL (interquartile range, 1500–4260 mL). The median duration from the first amnioreduction until delivery was 26 days (interquartile range, 15–52.5 days). There was no significant association between gestation at delivery and the volume per procedure or total volume that was removed. Earlier gestation at first drain was associated positively with earlier gestations at delivery. In 4.1% of amnioreduction procedures (11/271 procedures), there was an unplanned preterm birth within 48 hours. The median gestation at delivery was 36.4 weeks (interquartile range, 34–38 weeks). The final diagnoses were gastrointestinal malformations (21%), idiopathic polyhydramnios (20.3%), chromosomal anomaly (15.2%), syndromic condition (13.7%), and neurologic condition (8%).
Conclusion
Amnioreduction has a useful role in the management of polyhydramnios in singleton pregnancies. Complications are uncommon, and delivery typically occurs near term.
The accuracy of ultrasound evaluation of amniotic fluid volume in singleton pregnancies: the effect of operator experience and ultrasound interpretative technique.
The severity of polyhydramnios varies, and there are several subclassifications based on either amniotic fluid index or maximal vertical pocket (MVP) to reflect this variance.
Polyhydramnios reflects a final common pathway of several obstetric events such as fetal abnormalities, placental tumors, maternal diabetes mellitus, and fetal anemia. However, in 40-50% of cases no cause is evident prenatally, and the polyhydramnios is classified as idiopathic; however, in approximately 10% of cases, an abnormity is identified after delivery.
Once a diagnosis of polyhydramnios is made and investigations for potential causes are performed, the subsequent management of the pregnancy can be problematic, particularly in severe cases, because of issues that surround maternal discomfort and the risk of preterm birth. Amnioreduction, widely used in the management of twin-twin transfusion syndrome (TTTS) in monochorionic twin pregnancies before the introduction of placental laser ablation, is an option that is available to palliate maternal symptoms and that potentially can prolong the pregnancy. Although there is a large volume of literature available on amnioreduction in TTTS,
A recent metaanalysis to evaluate the complications of amnioreduction in singleton pregnancies could identify only 4 small cases series over a 20-year period.
Given the paucity of data available on a procedure that anecdotally appears to be offered by most fetal medicine units, we retrospectively reviewed all cases of amnioreduction that were performed in singleton pregnancies in our institution during the 13-year period of 2000-2012. The aim of our study was to review the indications, procedural complications, and outcomes of singleton pregnancies that were complicated by polyhydramnios of a severity warranting amnioreduction.
Materials and Methods
This was a retrospective review of women who were referred to King Edward Memorial Hospital for Women, Perth, Western Australia, with polyhydramnios that complicated a singleton pregnancy that underwent at least 1 amnioreduction procedure between January 2000 and December 2012. Cases were identified from interrogation of the ultrasound department Radiology Information System (IMPAX; Agfa HealthCare, Mortsel, Belgium) with the use of the coding key terms amnioreduction, amniocentesis, and fetal invasive procedure. Images that were stored on the Picture Archiving and Communication System and reports of the cases that had been ascertained with this process were then reviewed manually to capture the data of those women who received an amnioreduction. The institutional fetal medicine unit database was independently searched under the key words of amnioreduction, amniodrainage, and amniocentesis to maximize case ascertainment. All identified cases were then reviewed with the use of the maternal and child medical record chart, the hospital electronic clinical information management system (iSOFT IBA Health Group, Sydney, Australia), and the Picture Archiving and Communication System IMPAX imaging system, with regard to the maternal and fetal characteristics, pregnancy outcome, and, for survivors, the short-term outcomes. Our hospital is the sole tertiary referral center for the state of Western Australia, and amnioreduction is performed at our center only. Therefore, this case series represents the experience of our entire state obstetric population over a 13-year period, during which approximately 335,000 singleton births at >20 weeks’ gestation occurred.
Joyce A, Hutchinson M. Western Australia’s mothers and babies, 2010: twenty-eighth annual report of the Western Australian Midwives’ Notification System. Department of Health. East Perth, Western Australia; Department of Health; 2012.
The investigational protocol was approved by the King Edward Memorial Hospital Institutional Ethics Committee before commencement of the study.
Our institutional protocol for the assessment of pregnancies that are complicated by polyhydramnios involves a detailed ultrasound assessment of the fetus and placenta, plus screening for red cell antibodies, diabetes mellitus, and infection. Amniocentesis is performed if the preceding investigations are suggestive of a chromosomal anomaly, infection, or other condition in which amniotic fluid analysis may be diagnostic (eg, cystic fibrosis, skeletal dysplasia). Amnioreduction was performed in women who were symptomatic from the excess amniotic fluid (eg, maternal abdominal pain, dyspnea) and with a MVP of ≥8 cm at the initial ultrasound scanning for whom the attending fetal medicine specialist believed that the procedure would benefit the pregnancy management. The decision for amnioreduction was made on a case-by-case basis.
Amnioreduction was not performed in women with a coagulation disorder and a maternal infection with the potential for perinatal transmission such as HIV and who were in active labor or for whom delivery was considered inevitable in the short-term. The amniotic fluid was sent for fetal karyotyping in all cases if this had not been performed previously and for microbiologic studies when there was potential for a congenital infection. The technique that was used for amnioreduction was uniform during the study period. All women received a premedication of intramuscular morphine and promethazine approximately 30 minutes before the amniotic fluid aspiration was conducted. After maternal positioning and identification, by ultrasound scanning, of the most suitable site for the drain, an 18-gauge spinal needle (Becton Dickinson, North Ryde, NSW, Australia) was inserted transabdominally under continuous ultrasound guidance. Transplacental needle insertion was avoided. After the collection of amniotic fluid samples, if required, the insertion needle was connected with extension tubing to an electronic vacuum pump and drainage bottle, initially a Clements Inter-Vac (BMDi TUTA Health Care Pty Ltd, North Sydney, Australia) and since 2005 a Hamou Endomat (Karl Storz Tuttlingen, Germany). The amnioreduction was performed under continuous ultrasound guidance to minimize fetal contact and to permit continuous aspiration as the uterine size altered with the reduction in volume. Amniotic fluid was removed at a rate of 100-125 mL/minute. The volume of amniotic fluid removed was dependent on the operator and the clinical situation (eg, maternal uterine activity, fetal position), but in general was restricted to no >2000-2500 mL per procedure.
Data were collected and collated for all women on maternal characteristics, ultrasound findings, cause of polyhydramnios when known, procedural information that included complications, and pregnancy outcome that included the final perinatal diagnosis. Data on the surviving children were obtained through the medical record charts and iSOFT electronic clinical management system of the sole tertiary pediatric hospital in our state.
Numeric variables are presented as median (interquartile range [IQR]) and categoric data are presented as a number (percentage). Linear regression was used to assess the relationship between total fluid volume removed and gestation at delivery outcomes with gestation at the initial amnioreduction procedure. Total fluid volume was log transformed for analysis to achieve normality of residuals. Statistical analysis was performed using IBM SPSS Statistics for Windows (version 20.0; IBM Corporation, Armonk, NY). All statistical tests were 2-sided, and a probability value of < .05 was considered statistically significant.
Results
During the study period 138 women with symptomatic polyhydramnios that complicated a singleton pregnancy underwent 271 amnioreduction procedures at our institution. The maternal and pregnancy characteristics are presented in Table 1. The median gestation at the time of the first amnioreduction was 31.4 weeks (IQR, 28.4–34 weeks; Figure 1). Most women received only 1 amnioreduction, although there was a wide range of procedural numbers (1-17) and 63 of the women (45.6%) required >1 amnioreduction (Table 1). The median volume of amniotic fluid removed per procedure was 1750 mL (IQR, 1400–2050 mL); the median volume drained per pregnancy was 2100 mL (range, 500–37,500 mL) and the median MVP at the conclusion of the amnioreduction was 5.8 cm (IQR, 4.8–6.8 cm). Delivery occurred at a median of 36.4 weeks' gestation (range, 23.2–41.2 weeks) with a median prolongation of the pregnancy from the time of the first drain until birth of 3.7 weeks (range, 0–16.1 weeks; Table 1).
Table 1Maternal and procedural characteristics (n = 138)
Fetal anomalies were the predominant reason for the severe polyhydramnios and varied from structural to functional abnormalities (Table 2). Fetal anomalies were responsible for 77.5% of the cases (107/138) and 84.9% of the amnioreduction procedures (230/271); gastrointestinal obstructive lesions were numerically the most frequent indication for amniotic fluid drainage. There were 11 cases of isolated duodenal atresia and an additional 5 cases of complicating trisomy 21; the latter cases have been classified under chromosomal anomalies. It is notable that, of the 5 cases of euploid congenital diaphragmatic hernia that required amnioreduction (4 left-sided and 1 right-sided), 4 fetuses died neonatally; only 1 fetus survived. In 22 of 138 cases (15.9%), there was no clear cause for the polyhydramnios in the perinatal period; although on longer term follow-up evaluation, 2 children had cerebral palsy (both delivered at 37 weeks’ gestation for breech presentation), and 1 child has severe sensorineural deafness caused by a connexin gene anomaly.
Table 2Cause of the cases of polyhydramnios that required amnioreduction
Complications after amnioreduction are presented in Table 3. The most common complications were preterm birth within 48 hours of an amnioreduction (4.1% of all procedures) or preterm prelabor rupture of membranes (1.1% of all procedures). The fetus had a known lethal anomaly in 5 of the 11 cases that delivered within 48 hours of an amnioreduction. Cervical length before amnioreduction was not measured routinely. There was no significant association between the gestation at first amnioreduction and the total volume removed (P = .592; Figure 2). Gestation at the first amnioreduction was associated positively with later gestation at delivery (mean effect, 3.48; 95% confidence interval, 0.69–6.27; P = .015) but at a reducing rate as gestation approached term (mean effect of squared term, –0.05; 95% confidence interval, –0.09 to –0.003; P = .038; Figure 3).
Of the 138 fetuses in this cohort, 40 have died (38.9%; Table 4). There were 16 stillbirths that comprised 12 spontaneous fetal death cases and 4 terminations of pregnancy. The reasons for the pregnancy terminations were 1 case each of Pallister Killian syndrome, bilateral intracerebral hemorrhage with hydrocephalus, fetal akinesia, and nonimmune hydrops. Neonatal death occurred in 20 cases (14.5%); 9 deaths (45%) occurred in the first 24 hours after birth because of severe respiratory compromise or planned perinatal palliative care. There were 4 late deaths that occurred at 7 weeks (bronchopulmonary dysplasia and cardiac anomaly), 10 months (short-bowel syndrome), 11 months (Miller Dieker syndrome), and 12 months (cardiac failure because of tricuspid valvular disease). We did not have the capacity to assess long-term morbidity of survivors in this study.
This series of amnioreduction procedures in singleton pregnancies that were complicated by symptomatic polyhydramnios has demonstrated 3 main features. First, there is a strong association of excessive amniotic fluid volume and adverse fetal outcomes. Most fetuses with polyhydramnios in our series had a significant structural or functional problem, and 1 in 3 died either perinatally or within the first year of life. Second, there is an apparent effectiveness of large-volume amnioreduction in prolonging gestation, which is similar to that observed with amnioreduction in TTTS.
Delivery in our cohort occurred at a median of 36 weeks' gestation, which is likely to be particularly beneficial for those fetuses who require neonatal surgery. Third, the complication rate from large-volume amnioreduction was not high, especially when considering the high risk of preterm birth that typically is associated with severe polyhydramnios.
Amnioreduction, the removal of large volumes of amniotic fluid, has long been used as a component in the management of severe polyhydramnios and is offered by most fetal medicine units. The technique has undergone progressive procedural modifications over the past 3 decades, from 1 of passive gravitational drainage through to a syringe manual aspiration technique with a 3-way tap until the current process of continuous aspiration with an electronic vacuum device. Passive gravitational drainage is a slow technique that typically does not permit the removal of large volumes of amniotic fluid and was replaced in the early 1990s in our unit by a syringe technique with a 3-way tap and manual aspiration with a 50-mL syringe. The syringe technique also does not allow rapid removal of amniotic fluid and results in significant discomfort for the operator because of the repetitive aspiration movements that are required. In the mid and late 1990s, reports appeared of the use of vacuum bottle aspiration systems for the removal of large volumes of amniotic fluid in women with polyhydramnios.
Despite some initial concerns that the rapid removal of large volumes of amniotic fluid may result in placental abruption, preterm labor, or membrane rupture,
this does not appear to be a frequent occurrence. In our series of 271 large-volume amnioreduction procedures (with volume removal rates of 100-125 mL/min), the occurrence of preterm birth within 48 hours of the procedure was 4.1%, and the occurrence of premature rupture of membranes was 1.1%. Procedural complication rates recently have been reported in a systematic review of 4 case series of amnioreduction procedures in singleton pregnancies.
Delivery within 48 hours of the procedure occurred in 1 of 47 cases (2.1%), with other outcomes difficult to quantify because of small case numbers. Given that these pregnancies are at increased risk for preterm birth and membrane rupture, it is unclear as to the precise contribution of the drainage procedure to these outcomes. We did not have access to robust data on maternal symptoms after the amnioreduction procedure, although anecdotally symptom relief was the typical maternal response.
Interestingly, there are few published series on amnioreduction in singleton pregnancies; to date, all of them have been characterized by small case numbers or combined with data from multiple pregnancies that were complicated by TTTS, where the pathophysiologic condition is quite different.
reported on 70 women who received 130 amnioreduction procedures with the use of a vacuum wound-drainage system in 2004. Within this data set were 33 women with TTTS (80/130 procedures) and 4 women with a dichorionic twin pregnancy. Thus, there were 33 women with a singleton pregnancy (47%) in the study population who received 45 drainage procedures. The mean gestation at initial drain was 31 weeks in the non-TTTS cohort, which is very similar to that in our study, and most pregnancies were complicated by fetal anomalies. There was 1 procedure-related complication in the singleton cohort that occurred at 32 weeks gestation in a woman with unexplained polyhydramnios with premature rupture of membranes within 48 hours of a 600-mL drain. In a small case series of 10 singleton pregnancies that required at least 1 amnioreduction for polyhydramnios (15 procedures in total), Piantelli et al
reported a pregnancy prolongation of 18 days (range, 0–42 days) with a median gestation at first procedure of 30 weeks and a delivery median of 32 weeks. There was a highly successful reduction in maternal symptoms in this cohort (100% resolution of dyspnea). Two women delivered after the first drainage procedure, and there was 1 placental abruption that resulted in a neonatal death. In 2013, a systematic review reported on 4 studies that were published between 1994 and 2004 and incorporated a total of 100 women.
The authors were not able to quantify individual procedural complication rates because of small numbers and failure to report all complications by all authors. The addition of our series to the obstetric literature increases the objective knowledge base of the outcomes for singleton pregnancies that are complicated by polyhydramnios severe enough to warrant amnioreduction.
Most fetuses in this cohort had a pre- or postnatally recognizable problem that would reasonably account for the severe polyhydramnios. It has been previously shown that the more severe the polyhydramnios the higher the likelihood of a fetal anomaly.
In the cases that appeared to be truly isolated at the time of neonatal discharge, 2 of 22 cases (9.1%) were diagnosed subsequently with cerebral palsy in childhood. Clearly, for women with symptomatic polyhydramnios, the likelihood of a fetal problem is high, and the chance of that problem being associated with a complicated outcome is similarly high, but not universal. While the outcome of the pregnancy was fundamentally a consequence of the primary fetal diagnosis, the prolongation of the pregnancy in those cases that required early neonatal surgery (predominantly gastrointestinal anomalies such as duodenal atresia) is likely to be beneficial in terms of anesthesia risk and postoperative care.
The strength of this study lies in the size of the study cohort, its state-wide population base, and the uniform amnioreduction protocol that is used. This was a retrospective study and thus has some obvious weaknesses, which include the absence of robust data on maternal symptoms before and after the amnioreduction procedures, variability in the amount of amniotic fluid removed per procedure, the absence of accurate information on the duration of each procedure, the deficiency of data on cervical length, and the lack of a control group. There were several medical practitioners in our unit who performed the amnioreduction procedures, both maternal fetal medicine specialists and fellows in training. We do not see this as a study weakness necessarily; indeed this practitioner variability increases the generalizability of the study to all units with the facility for amnioreduction and can reassure units that a low complication rate typically accompanies large-volume drainage of amniotic fluid in polyhydramnios.
We conclude that large-volume amnioreduction for symptomatic polyhydramnios in singleton pregnancies has a role in contemporary fetal medicine practice. The use of vacuum-assisted aspiration devices facilitates the rapid removal of large volumes of amniotic fluid with low complication rates and may prolong gestation, which could be advantageous for situations in which neonatal surgical intervention is required. There is a need for ongoing research in the clinical management of severe polyhydramnios to assess the role of medical therapies compared with amnioreduction, the predictive role of cervical length in polyhydramnios and its influence on latency from drainage until delivery, and a better definition of the capacity of amnioreduction to prolong pregnancy.
References
Magann E.F.
Chauhan S.P.
Doherty D.A.
Lutgendorf M.A.
Magann M.I.
Morrison J.C.
A review of idiopathic polyhydramnios and pregnancy outcomes.
The accuracy of ultrasound evaluation of amniotic fluid volume in singleton pregnancies: the effect of operator experience and ultrasound interpretative technique.
Joyce A, Hutchinson M. Western Australia’s mothers and babies, 2010: twenty-eighth annual report of the Western Australian Midwives’ Notification System. Department of Health. East Perth, Western Australia; Department of Health; 2012.
Cite this article as: Dickinson JE, Tjioe YY, Jude E, et al. Amnioreduction in the management of polyhydramnios complicating singleton pregnancies. Am J Obstet Gynecol 2014;211:434.e1-7.
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