Abstract
BACKGROUND:
Twin reversed arterial perfusion (TRAP) sequence is a rare condition that affects primarily monozygotic monochorionic twin pregnancies in which a normal twin acts as a pump (donor) for an acardiac recipient (perfuse) twin.
OBJECTIVE:
We report our experience over the last 13 years at a tertiary health care center.
DESIGN:
Descriptive, retrospective case series
SETTING:
Tertiary health care center
PATIENTS AND METHODS:
All TRAP cases managed between the years 2009 and 2022 at our Fetal Diagnosis and Therapy Center were included. Data recorded included demographic and clinical information which was used to generate descriptive data. Patients were managed by a multidisciplinary team with variable interventions.
MAIN OUTCOME MEASURE:
Survival of normal twin
SAMPLE SIZE:
Eight
RESULTS:
Eight pregnant women with TRAP syndrome were managed at our center during that period. One was monozygotic monochorionic and the others were monochorionic diamniotic. Median maternal age at presentation was 27 years and median gestational age at diagnosis was 23 weeks. All were diagnosed with ultrasound (US) imaging. Three were managed with bipolar ligation of the cord of the acardiac twin under general anesthesia, one US-guided (single port) and 2 fetoscopic (2 ports) with a median operative time of 39 minutes. The last five cases were managed with US-guided radiofrequency ablation (RFA) under local anesthesia, one needed 2 sessions, 1 week apart. The median duration of the RFA procedure was 23 minutes. There were no complications and all had viable normal babies born at a median of 32 weeks of gestation (6 C-section, 2 spontaneous membrane rupture).
CONCLUSIONS:
Acardiac twin cord ligation and RFA are feasible and safe options with excellent outcome for TRAP syndrome. RFA may be preferable owing to its less invasiveness under local anesthesia.
LIMITATIONS:
None, given the rarity of the disease and the study design.
CONFLICT OF INTEREST:
None.
INTRODUCTION
Twin reversed arterial perfusion (TRAP) sequence is a very rare condition that affects primarily 1-2.6% of monozygotic monochorionic twin pregnancies.1–3 It has an estimated prevalence rate of approximately 1 in 35 000 pregnancies. The normal twin acts as a pump (donor) for an acardiac recipient (perfuse) twin due to the presence of abnormal vascular anastomoses.4,5 As a result, the pump twin’s heart has to meet the demands of both twins as the acardiac twin grows. The pump twin may develop a significant strain that could lead to heart failure with its devastating consequences. The TRAP mortality rate can be as high as 52% if not treated6 and 30% of pump twins are expected to die before 16 weeks of gestation.7 We report our experience with the management of TRAP at a tertiary health care center.
PATIENTS AND METHODS
A retrospective chart review was conducted of patients referred to our center for management of TRAP over the period from April 2009 to April 2022 (13 years). Demographic and clinical data were collected and descriptive data were generated. Clinical data included gestational age at diagnosis, symptoms and signs at presentation, timing of intervention, type of intervention, and outcome.
Three methods of fetal intervention (acardiac twin cord occlusion) were used: 1) Cord ligation with bipolar coagulation under ultrasound (US) guidance (1 case): Under general anesthesia, using sterile technique, an access point on the abdomen was found with US and an 11 FR angio-catheter is inserted using the Seldinger technique under US guidance. The bipolar grasper was introduced and the cord of the acardiac twin grasped under US-guidance and occluded first with no coagulation. When blood flow ceased in the umbilical cord of the acardiac twin and the donor twin’s cord was confirmed patent, the bipolar coagulation was started to occlude the acardiac twin’s cord; 2) Cord ligation with bipolar coagulation under fetoscopic guidance (2 cases): Under general anesthesia, the above technique is utilized to insert 2 angio-catheters. Under fetoscopic guidance, the cord of the acardiac twin was occluded with bipolar coagulation under vision; 3) Radiofrequency ablation (RFA) (5 cases): RFA was done using the RF 3000TM system (Boston Scientific) with LeVeen superslim needle electrodes (Boston Scientific). The electrodes had a 17-gauge cannula and a 15-cm long by 2-cm wide expandable umbrella with 8 tines. The needle was inserted under sterile technique and local anesthesia (1% xylocaine) with US guidance. The tip was placed beside the vessels of the umbilical cord of the acardiac twin. The insertion was on the fetal side in three cases and on the placental side in the other two cases. Once the needle was positioned, the expandable tines were deployed and the energy delivered. RFA was performed by a maternal-fetal medicine specialist but interventional radiologists supervised the first two procedures to ascertain proper and accurate use of the technology and device. The entire procedure was conducted under US guidance and imaging of the normal fetus to ensure its safety. Patients were admitted usually for 1 day with US imaging the next day to ensure viability of the normal fetus and no recanalization of the obliterated vessels. Patients were then followed up at our obstetric clinics and observed for complications related to the intervention and received regular obstetric care. The study was approved by the Office Of Research Affairs at King Faisal Specialist Hospital with a consent waiver given the retrospective nature of the study and the lack of patient identification. The research was conducted ethically in accordance with the World Medical Association Declaration of Helsinki. The proposal was reviewed by the clinical research committee on human research (RAC Number is 2221229).
RESULTS
Eight pregnant women with TRAP sequence were managed at our center during that period (Table 1). All were referred from other centers for fetal intervention. Median maternal age at presentation was 27 (range, 22–33) years and median gestational age (GA) at diagnosis was 23 range, (17–27) weeks. All had a fetal echocardio-gram which showed a normal heart in pump twins in six patients; one twin had a small ventricular septal defect, and one twin had a large heart with a large umbilical vein. All were monochorionic diamniotic types except one that was monochorionic monoamniotic. All cases were large acardiac twins (abdominal circumference ratio is >50%) of the acardiac acephalus type. Three were managed with bipolar ligation of the cord of the acardiac twin under general anesthesia, one US-guided (single port) and two fetoscopic (2 ports) with a median operative time of 39 minutes. The last five cases were managed with US-guided radiofrequency ablation (RFA) under local anesthesia; one needed two sessions 1 week apart. The RFA procedure had a median duration of 23 minutes. Patients who had RFA needed 40 watt cycles for 5-10 minutes to occlude the vessels, and one that required redo of the RF needed higher energy (70 watt for 11 minutes). There were no complications and all had viable normal babies (pump twins) born at a median of 32 weeks (range, 29-38 weeks) of gestation. Six patients had C-sections (median GA, 33 weeks) and 2 had premature rupture of the membranes with vaginal delivery (GA, 31 and 32 weeks).
Table 1.
Descriptive data and outcome results.
| Patient serial number | Mother's age (years) | Gestational age at diagnosis (weeks) | Fetal intervention | Gestational age at delivery (weeks) | Mode of delivery |
|---|---|---|---|---|---|
| 1 | 26 | 18 | US-guided bipolar coagulation | 29 | Urgent C-section for oligohydramnios |
| 2 | 30 | 23 | Fetoscopic-guided bipolar coagulation | 31 | Premature rupture of membranes/vaginal delivery |
| 3 | 22 | 23 | Fetoscopic-guided bipolar coagulation | 34 | Elective C-section |
| 4 | 27 | 23 | Radiofrequency ablation | 32 | Premature rupture of membranes/vaginal delivery |
| 5 | 30 | 26 | Radiofrequency ablation | 30 | Emergency C-section for fetal distress |
| 6 | 33 | 27 | Radiofrequency ablation | 35 | Elective C-section |
| 7 | 25 | 24 | Radiofrequency ablation | 32 | Elective C-section |
| 8 | 26 | 17 | Radiofrequency ablation | 38 | Elective C-section |
DISCUSSION
TRAP sequence is a rare condition that affects monochorionic twin pregnancies; the first case was described in 1533.2 The first reported prenatal diagnostic features of the anomaly were described in 1978.8 The TRAP sequence is considered an extreme form of the more common twin-twin transfusion syndrome. Despite its rarity, the TRAP sequence gained great attention in the literature with many reports in recent decades because of the significant malformation of the acardiac twin (called a “monster” in old reports) with loss of the healthy normal twin (donor) prenatally. The etiology of the TRAP sequence is generally unknown but some theories have been offered. A defective cardiac embryo-genesis caused by abnormal genes may lead to the deformed twin and its dependency on the normal one.9 Another theory suggests that the resulting acardiac twin is secondary to a severe steal syndrome via abnormal vascular anastomoses of the placenta,10,11 which could lead to hypoxia leading to organ atrophy, including the heart.12 The latter notion was supported by a report on the autopsy of an acardiac twin showing an atrophic fetal myocardium.13 Acardiac twins are classified based on morphology8,14 and size.15 Morphologically, acardius acephalus (absent cranial and thoracic structures with malformed upper extremities) is the most common. Other types include acardius anceps (developed body but deformed cranial/facial elements), acardius amorphous (very deformed mass), and acardius acormus (some cranial structures only). This morphological classification has no prognostic value and has no impact on management. Size of the acardiac twin can be divided into small or medium (type I: abdominal circumference ratio <50%) and large (type II: abdominal circumference ratio >50%). The latter types can be divided further in subtypes “a” (no signs of heart failure in the donor twin) and “b” (signs of heart failure in the donor twin). The size of the acardiac twin is prognostic and considered one of the determinant factors for fetal intervention.
Diagnosis of TRAP sequence is usually done with US imaging where a dichorionic twin pregnancy shows morphological abnormality16 with major size (weight) discrepancy between the twins, and absent heart and other malformations of other structures in the acardiac twin. In particular, the presence of paradoxical circulation (arterial blood flow towards the twin rather than away from it) in the acardiac twin is considered pathognomonic.17 With complicated cases, polyhydramnios, signs of heart failure in the donor twin, and subcutaneous edema and fluid collection in the acardiac twin17 are detected.
TRAP sequence carries a high mortality rate (~50%) for the normal cardiac (donor) twin if untreated secondary to intrauterine congestive heart failure and prematurity due to polyhydramnios.6,7,9,15 Other reports added the possibility of growth restriction of the donor twin and secondary reversal of the blood flow towards the donor twin with deoxygenated blood.16
The primary goals in managing TRAP sequence patients are the preservation of the life of the donor twin and prevention of polyhydramnios to avoid prematurity. These two goals may limit the fetal intervention for larger acardiac twins and complicated cases (polyhydramnios and heart failure in the donor twin). Nevertheless, expectant management of TRAP sequence still carries a risk of donor twin loss without apparent complications.7 Some centers involve patients in the decision making in the absence of complications.18 Although classification of TRAP was offered to help decision making related to the intervention, the timing of intervention is widely debatable. Recently, many authors have recommended early prophylactic intervention due to the high rate of pump twin demise without alerting signs and the successful early (first trimester) interventions.18–20 Moreover, the monochorionic monoamniotic type of TRAP sequence may theoretically have a higher risk of cord entanglement that could lead to the intrauterine demise of the pump twin. This may be taken into account when contemplating a decision for this type of TRAP case and may necessitate an early fetal intervention regardless of the development of complications. Although plausible, there are no data on TRAP sequence outcome specific to monoamniotic twin pregnancies relative to cord entanglement that support early fetal intervention regardless of complications. Furthermore, data from monoamniotic twin pregnancies in general showed that the risk of cord entanglement is low after 20 weeks of gestation.21 In our series, we elected to use the bipolar coagulation of the umbilical cord of the acardiac twin without division under fetoscopic guidance (two ports) in the case of the monochorionic monoamniotic type due to the fact that the cord had a marginal insertion on the placenta and runs on its surface; hence, there was a low risk of entanglement with the cord of the donor twin.
There are many options to manage patients with the TRAP sequence, and fetal interventions have evolved over the years. Historically, medical agents were given to combat heart failure and premature labor.22,23 Amnioreduction was also offered for patients with polyhydramnios.24 Lately, disrupting the blood supply of the acardiac twin has become the mainstay of management of TRAP.9 The latter was initially (1989) performed invasively via hysterotomy, but in recent decades, more innovative, less invasive techniques have been developed. The cord of the acardiac twin has been occluded successfully with many methods including percutaneous coil embolization,25 ligation under fetoscopy,26 ultrasound-guided extracorporeal ligation,27 US-guided thrombogenic agents occlusion,28 US-guided thermocoagulation,29,30 and fetoscopic laser photocoagulation.31 US-guided intra-fetal ablation has also been introduced to disrupt blood flow to the acardiac twin. The latter includes sclerosing agents,32 laser photocoagulation,18–20 high-intensity focused US,33 and US-guided RFA.34–36 The needle-based ultrasound-guided intra-fetal options seem to be gaining popularity lately due to being relatively less invasive, with greater feasibility and improved safety at an early gestational application. These options are also of comparable, if not greater, effectiveness compared to cord occlusion options. Although more comparative studies between the intra-fetal and cord occlusion options are needed,37 recent reports are encouraging.34
Our data are retrospective for patients who were mostly diagnosed elsewhere and referred for intervention; hence, our conclusions cannot be generalized across the management scheme of TRAP. Nonetheless, the results are valid relative to the effectiveness of the management methods used and had an excellent survival rate (100%). Specifically, our experience with RFA was superb with good outcomes and no complications.
In conclusion, our data have shown that acardiac twin cord ligation and RFA are feasible and safe options with excellent outcomes for TRAP syndrome. RFA may be preferable owing to being less invasive under local anesthesia. Although our study was not designed to address the indications and timing of intervention, review of the available data in the literature and the encouraging results of fetal interventions (especially the needle-based ultrasound guided intra-fetal options) support an early intervention to maximize survival of the normal twin.
AUTHOR CONTRIBUTIONS
Saud AlShanafey, Gawaher Almutairi: collection of data; Saud AlShanafey: data analysis, drafting the manuscript and finalizing, and submission; Saud AlShanafey, Wesam Kurdi, Maha Alnemer, Maha Tulbah, Rubina Khan, Nada AlSahan, Maisoon Almugbil, Fahad AlHazzani: interpretation of data, review of manuscript
DATA AVAILABILITY STATEMENT
Data are stored on a computer that belongs to the fetal diagnosis and therapy program and managed by the director and coordinator of the program. Basic data were entered prospectively for all patients and extra data can be collected from the electronic medical records as needed. Data are secure and can only be shared if necessary with permission from the medical records department and data warehouse.
Funding Statement
None
REFERENCES
- 1.James WH. A note on the epidemiology of acardiac monsters. Teratology 1977;16:211–216 [DOI] [PubMed] [Google Scholar]
- 2.Napolitani FD, Schreiber I. The acardiac Monster. A review of the world literature and presentation of 2 cases. Am J Obstet Gynecol 1960;80:582–589 [DOI] [PubMed] [Google Scholar]
- 3.van Gemert MJ, van den Wijngaard JP, Vandenbussche FP. Twin reversed arterial perfusion sequence is more common than generally accepted. Birth Defects Res A Clin Mol Teratol 2015; 103:641–643 [DOI] [PubMed] [Google Scholar]
- 4.Lewi L, Deprest J, Hecher K. The vascular anastomoses in monochorionic twin pregnancies and their clinical consequences. Am J Obstet Gynecol 2013;208:19–30 [DOI] [PubMed] [Google Scholar]
- 5.van Gemert MJ, Ross MG, Nikkels PG, Wijngaard JP. Acardiac twin pregnancies part III: Model simulations. Birth Defects Research Part A: Clinical and Molecular Teratology. 2016. Dec;106(12):1008–15 [DOI] [PubMed] [Google Scholar]
- 6.Moore TR, Gale S, Benirschke K. perinatal outcome of forty-nine pregnancies complicated by acardiac twinning. Am J Obstet Gynecol 1990; 163:907–912 [DOI] [PubMed] [Google Scholar]
- 7.Lewi L, Valencia C, Gonzalez E, Deprest J, Nicolaides KH. The outcome of twin reversed arterial perfusion sequence diagnosed in the first trimester. American journal of obstetrics and gynecology. 2010. Sep 1;203(3):213–e1. [DOI] [PubMed] [Google Scholar]
- 8.Lehr C, Dire J. Rare occurrence of a holoacardious acephalic monster: sonographic and pathologic findings. J Clin Ultrasound 1978; 6:259–261 [DOI] [PubMed] [Google Scholar]
- 9.Van Allen MI, Smith DW, Shepard TH. Twin Reversed Arterial Perfusion (TRAP) sequence: study of 14 twin pregnancies with acardius. Semin Perinatol 1983; 7:285–293 [PubMed] [Google Scholar]
- 10.Hecher K, Ville Y, Nicolaides KH. Color Doppler ultrasonography in the identification of communicating vessels in twin-twin transfusion syndrome and acardiac twins. J Ultrasound Med 1995; 14: 37–40 [DOI] [PubMed] [Google Scholar]
- 11.Shih JC, Shyu MK, Hunag SF, Jou HJ, Su YN, Hsieh FJ. Doppler waveform analysis of the intertwin blood flow in acardiac pregnancy: implications for pathogenesis. Ultrasound in Obstetrics and Gynecology: The Official Journal of the International Society of Ultra-sound in Obstetrics and Gynecology. 1999. Dec;14(6):375–9. [DOI] [PubMed] [Google Scholar]
- 12.Sogaard K, Skibsted L, Vibeke B. Acardiac twins: pathophysiology, diagnosis, outcome and treatment. Fetal Diagn Ther 1999; 14:53–59 [DOI] [PubMed] [Google Scholar]
- 13.Driggers RW, Blakemore KJ, Bird C, Ackerman KE, Hutchins GM. Pathogenesis of acardiac twinning: clues from an almost acardiac twin. Fetal diagnosis and therapy. 2002;17(3):185–7. [DOI] [PubMed] [Google Scholar]
- 14.Pepe F, Teodoro MC, Luca C, Privitera F. Conservative management in a case of uncomplicated trap sequence: a case report and brief literature review. Journal of Prenatal Medicine. 2015. Jul;9(3-4):29. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Wong AE, Sepulveda W. Acardiac anomaly: current issues in prenatal assessment and treatment. Prenat Diagn 2005; 25:796–806 [DOI] [PubMed] [Google Scholar]
- 16.Vitucci A, Fichera A, Fratelli N, Sartori E, Prefumo F.. Twin reversed arterial perfusion sequence: current treatment options. International Journal of Women’s Health. 2020. May 28: 435–43. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Sebire N, Sepulveda W, Jeanty P,. et al. In: Nyberg D, McGahan J, Pretorius D, Pilu G, editors. Diagnostic Imaging of Fetal Anomalies. Philadelphia: Lippincott Williams & Wilkins; 2003:777–813 [Google Scholar]
- 18.Berg C, Holst D, Mallmann MR, Gottschalk I, Gembruch U, Geipel A. Early vs late intervention in twin reversed arterial perfusion sequence. Ultrasound in Obstetrics & Gynecology. 2014. Jan;43(1):60–4. [DOI] [PubMed] [Google Scholar]
- 19.Pagani G, D’antonio F, Khalil A, Papa-georghiou A, Bhide A, Thilaganathan B. Intrafetal laser treatment for twin reversed arterial perfusion sequence: cohort study and meta-analysis. Ultrasound in Obstetrics & Gynecology. 2013. Jul;42(1):6–14. [DOI] [PubMed] [Google Scholar]
- 20.Tavares de Sousa M, Glosemeyer P, Diemert A, Bamberg C, Hecher K. First trimester intervention in twin reversed arterial per-fusion sequence. Ultrasound in Obstetrics & Gynecology. 2020. Jan;55(1):47–9. [DOI] [PubMed] [Google Scholar]
- 21.Dias T, Mahsud-Dornan S, Bhide A, Papageorghiou AT, Thilaganathan B. Cord entanglement and perinatal outcome in monoamniotic twin pregnancies. Ultra-sound in Obstetrics and Gynecology: The Official Journal of the International Society of Ultrasound in Obstetrics and Gynecology. 2010. Feb;35(2):201–4. [DOI] [PubMed] [Google Scholar]
- 22.Simpson PC, Trudinger BJ, Walker A, Baird PJ. The intrauterine treatment of fetal cardiac failure in a twin pregnancy with an acardiac, acephalic monster. American journal of obstetrics and gynecology. 1983. Dec 1;147(7):842–4. [DOI] [PubMed] [Google Scholar]
- 23.Ash K, Harman CR, Critter H. TRAP sequence –Successful outcome with indomethacin treatment. Obstet Gynecol 1990;76(5 pt 2):960–962 [PubMed] [Google Scholar]
- 24.Platt LD, DeVore GR, Bieniarz A, Benner P, Rao R. Antenatal diagnosis of acephalus acardia: a proposed management scheme. American journal of obstetrics and gynecology. 1983. Aug 1;146(7):857–9. [DOI] [PubMed] [Google Scholar]
- 25.Hamada H, Okane M, Koresawa M, Kubo T, Iwasaki H. Fetal therapy in utero by blockage of the umbilical blood flow of acardiac monster in twin pregnancy. Nihon Sanka Fujinka Gakkai Zasshi. 1989. Nov 1;41(11):1803–9. [PubMed] [Google Scholar]
- 26.McCurdy CM, Childers JM, Seeds Jw. Ligation of the umbilical cord of an acardiac-acephalus twin with an endoscopic intrauterine technique. Obstet Gynecol 1993;82(suppl):708–711 [PubMed] [Google Scholar]
- 27.Foley MR, Clewell WH, Finberg HJ, Mills MD. Use of the Foley Cordostat grasping device for selective ligation of the umbilical cord of an acardiac twin: a case report. American journal of obstetrics and gynecology. 1995. Jan 1;172(1):212–4. [DOI] [PubMed] [Google Scholar]
- 28.Tan TYT, Sepulveda W. Acardiac twin: a systematic review of minimally invasive treatment modalities. Ultrasound Obstet Gynecol 2003;22:409–419 [DOI] [PubMed] [Google Scholar]
- 29.Rodeck C, Deans A, Jauniaux E.. Thermocoagulation for the early treatment of pregnancy with an acardiac twin. N Engl J Med 1998;339:1293–1295 [DOI] [PubMed] [Google Scholar]
- 30.Hecher K, Lewi L, Gratacos E, Huber A, Ville Y, Deprest J. Twin reversed arterial per-fusion: fetoscopic laser coagulation of placental anastomoses or the umbilical cord. Ultrasound in Obstetrics and Gynecology: The Official Journal of the International Society of Ultrasound in Obstetrics and Gynecology. 2006. Oct;28(5):688–91. [DOI] [PubMed] [Google Scholar]
- 31.King JR, Conturie CL, Ouzounian JG, Korst LM, Llanes A, Chmait RH. Umbilical cord occlusion via laser coagulation in monochorionic multifetal gestations before and after 20 weeks of gestation. Fetal Diagnosis and Therapy. 2017;42(1):9–16. [DOI] [PubMed] [Google Scholar]
- 32.Sepulveda W, Bower S, Hassan J, Fisk NM. Ablation of acardiac twin by alcohol injection into the intra-abdominal umbilical artery. Obstetrics & Gynecology. 1995. Oct 1;86(4):680–1. [DOI] [PubMed] [Google Scholar]
- 33.Seo K, Ichizuka K, Okai T, Dohi S, Nakamura M, Hasegawa J,. et al. Treatment of twin-reversed arterial perfusion sequence using high-intensity focused ultrasound. Ultrasound in Obstetrics & Gynecology. 2019. Jul;54(1):128–34. [DOI] [PubMed] [Google Scholar]
- 34.Ozawa K, Wada S, Muromoto J, Sugibayashi R, Wada YS, Ito Y,. et al. Long-term neurodevelopmental outcomes of the pump twin in twin reversed arterial perfusion sequence treated by radiofrequency ablation. Prenatal Diagnosis. 2021. Nov;41(12):1575–81. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 35.Cabassa P, Fichera A, Prefumo F, Taddei F, Gandolfi S, Maroldi R,. et al. The use of radiofrequency in the treatment of twin reversed arterial perfusion sequence: a case series and review of the literature. European Journal of Obstetrics & Gynecology and Reproductive Biology. 2013. Feb 1;166(2):127–32. [DOI] [PubMed] [Google Scholar]
- 36.Lee H, Bebbington M, Crombleholme TM. The North American fetal therapy network registry data on outcomes of radio-frequency ablation for twin-reversed arterial perfusion sequence. Fetal Diagn Ther 2013;33:224–229 [DOI] [PubMed] [Google Scholar]
- 37.Abdel-Sattar M, Chon AH, Llanes A, Korst LM, Ouzounian JG, Chmait RH. Comparison of umbilical cord occlusion methods: radiofrequency ablation versus laser photocoagulation. Prenatal Diagnosis. 2018. Jan;38(2):110–6. [DOI] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
Data are stored on a computer that belongs to the fetal diagnosis and therapy program and managed by the director and coordinator of the program. Basic data were entered prospectively for all patients and extra data can be collected from the electronic medical records as needed. Data are secure and can only be shared if necessary with permission from the medical records department and data warehouse.