Objective
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.
Polyhydramnios, the presence of excessive amniotic fluid volume, has a reported prevalence of 1-2%. It has been defined variously, typically based on ultrasound criteria, as an amniotic fluid index >25 cm, maximal vertical pocket ≥8 cm, or the visual assessment of increased amniotic fluid volume by a sonographer. 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. There is a recognized association of polyhydramnios and adverse pregnancy outcomes that include perinatal death, fetal abnormality, and preterm birth.
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, there are much fewer data published on amnioreduction in singleton pregnancies. 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. 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 ).
| Variable | Measure |
|---|---|
| Maternal age, y a | 32 (27–35.5) |
| Parity, n a | 1 (1–2) |
| Male sex, n | 76 (55.1%) |
| Gestation at first amnioreduction, wk a | 31.4 (28.4–34) |
| Median amnioreduction per pregnancy, n a | 1 (1–2) |
| Volume removed per pregnancy, mL a | 2100 (1500–4260) |
| Gestation at delivery, wk a | 36.4 (34–38) |
| Interval first drain-delivery, wk a | 3.7 (2.1–7.5) |
| Cesarean delivery | 72 (52.2%) |
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.
| Condition | Total, n (%) a | Amnioreduction, n (%) b |
|---|---|---|
| Fetal abnormality | 107 (77.5) | 230 (84.9) |
| Gastrointestinal | 29 (21) | 58 |
| Tracheoesophageal fistula | 9 | |
| Duodenal atresia | 11 | |
| Meconium peritonitis | 6 | |
| Chromosomal | 21 (15.2) | 36 |
| Trisomy 21 | 10 | |
| Trisomy 18 | 4 | |
| Syndromes | 19 (13.7) | 49 |
| Noonan | 4 | |
| Charge | 3 | |
| Beckwith | 2 | |
| Costello | 2 | |
| Neurologic | 11 (8) | 29 |
| Fetal akinesia | 4 | |
| Myotonic dystrophy | 2 | |
| Respiratory | 8 (5.8) | 19 |
| Congenital diaphragmatic hernia | 5 | |
| Congenital cystic adenomatoid malformation | 2 | |
| Nonimmune hydrops | 6 (4.3) | 10 |
| Cardiac | 5 (3.6) | 11 |
| Skeletal | 4 (2.9) | 5 |
| Achondroplasia | 2 (1.4) | |
| Tumors | 4 (2.9) | 13 |
| Sacrococcygeal teratoma | 2 | |
| Placental | 2 (1.4) | 7 (2.6) |
| Chorioangioma | 2 | |
| Infection | 1 (0.7) | 1 (0.37) |
| Parvovirus | 1 | |
| Idiopathic | 28 (20.3) | 33 (12.2) |
| Diabetes mellitus | ||
| Type 1 | 3 | 3 |
| Type 2 | 3 | 4 |
| True idiopathic | 22 | 26 |
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