Dandy-Walker syndrome and monochorionic twins: insight into a possible etiological mechanism.

OBJECTIVE: Dandy-Walker syndrome (DWS) is a developmental malformation of the central nervous system characterized by complete or partial absence of the cerebellar vermis, the presence of a posterior fossa cyst, and ventriculomegaly. Although DWS can be seen with Mendelian and chromosomal disorders, the actual pathophysiologic mechanism responsible for the syndrome is unknown. The incidence of DWS is approximately 1-8/100,000 births. We have noted a higher than expected incidence of DWS in a population of twins referred as complicated monochorionic twins, to include twin-twin transfusion syndrome (TTTS). The purpose of this study was to assess the incidence of DWS in monochorionic twins. METHODS: The database of all patients referred with complicated monochorionic twins was queried for the diagnosis of DWS. TTTS was defined sonographically as the combined presence of a maximum vertical pocket (MVP) of >or=8 cm in the recipient and

In utero fetal oximetry via visible light spectroscopy in twin-twin transfusion syndrome.

OBJECTIVE: The purpose of this study was to assess fetal tissue venous oxygenation (StO2%) in utero during laser therapy for twin-twin transfusion syndrome via visible light spectroscopy (VLS). STUDY DESIGN: StO2% was measured in 10 donor and recipient twins at the level of the skin and placenta before and after laser therapy (SLPCV). RESULTS: Pre-SLPCV skin StO2% was significantly lower in the donor than in the recipient twin (21.6 +/- 6.2 vs 31.2 +/- 8.6, respectively; P = .01), but the difference disappeared after SLPCV. Placental surface StO2% measurements in 5 patients showed a significant increase in StO2% in the territory of the recipient (P = .04). Preoperative linear streaming as evidence of nonadmixing deoxygenated and oxygenated blood disappeared after SLPCV. CONCLUSION: In utero StO2% measurement is possible with VLS. Donor twins can have significantly less StO2% than recipient twins, but this is corrected after SLPCV. Further studies are warranted to determine the value of in utero VLS oximetry.

Fetal growth after laser therapy for twin-twin transfusion syndrome.

OBJECTIVE: The objective of the study was to compare twin weight discordance and prevalence of intrauterine growth restriction (IUGR) before laser therapy and after birth in pregnancies complicated by twin-twin transfusion syndrome (TTTS). STUDY DESIGN: Women with TTTS who underwent laser therapy with dual neonatal survivors born at least 28 days after surgery were studied. Estimated fetal weight (EFW) discordance at the preoperative sonogram and birthweight (BW) discordance were calculated. Weights below gestational age-corrected 10th percentile at sonogram and at birth for each twin were designated as IUGR. RESULTS: Among 211 women studied, the mean EFW discordance measured 26.6% and mean BW discordance was 18.4%, yielding a mean 8.2% decrease in weight discordance (P < .001). Comparing IUGR diagnoses before surgery and at birth, the recipient's proportion was unchanged (9.5% vs 7.1%, P = .353), whereas the donor's proportion decreased (64.5% vs 28.9%, P < .001). CONCLUSION: Twin weight discordance and donor fetus IUGR appear to improve after laser therapy for TTTS.

In utero laser treatment of type II vasa previa.

Vasa previa, defined as fetal vessels coursing within the membranes between the presenting part and the cervix, occurs in approximately 1:2500-5000 pregnancies. Type II vasa previa consists of fetal vessels crossing over the internal os connecting a bilobed placenta or a succenturiate lobe with the main placental mass. These vessels are prone to compression during labor or may tear when membranes rupture potentially resulting in fetal exsanguination and neonatal death. This complication could be avoided altogether if the vessels could be obliterated in utero. The purpose of this communication is to report the successful in utero laser ablation of type II vasa previa at 22.5 weeks of gestation. Subsequent ruptured membranes did not result in untoward fetal consequences. Risks and benefits of this novel procedure are discussed.

Sequential selective laser photocoagulation of communicating vessels in twin-twin transfusion syndrome.

OBJECTIVE: We have previously described the selective laser photocoagulation of communicating vessels (SLPCV) technique for the treatment of twin-twin transfusion syndrome (TTTS). Because TTTS is thought to result from a net transfer of blood from the donor twin to the recipient twin, we hypothesized that lasering the arteriovenous anastomoses from the donor to the recipient (AVDRs) first (sequential SLPCV or SQLPCV) would result in an improved hemodynamic status and decreased likelihood of intrauterine fetal demise of the donor twin (IUFD-D). MATERIALS AND METHODS: The diagnosis of TTTS was made by ultrasound showing the combined presence of a maximum vertical pocket > or = 8 cm in one sac and < or =2 cm in the other in a monochorionic/diamniotic twin pregnancy. Triplet pregnancies and monoamniotic pregnancies were excluded. Severity of TTTS was assessed using the Quintero staging system. All vascular anastomoses were endoscopically identified and classified as AVDR (AV from donor to recipient), AVRD (AV from recipient to donor), arterio-arterial (AA), or veno-venous (VV). The surgical procedure was coded as SQLPCV if all AVDRs were lasered first. Outcome measures included intrauterine fetal demise and perinatal survival. RESULTS: One hundred and ninety-three TTTS patients (137 SQLPCV, 56 SLPCV) underwent surgery from May 2003 to August 2005. Gestational age at surgery or at delivery, Stage, patent anastomoses, or persistent/reverse TTTS were not different between the groups. IUFD-D was significantly lower in the SQLPCV than in the SLPCV group (7.3% vs 21.4%, respectively, p = 0.005). Dual perinatal survival was significantly higher in the SQLPCV than in the SLPCV group (73.7% vs 57.1%, respectively, p = 0.02), although the incidence of at least one survivor was not different between the groups (90.5% vs 87.5%, respectively). Logistic regression showed SQLPCV, but not placental location, operating time or number of anastomoses to be significantly associated with a decreased likelihood of IUFD-D (p = 0.007). CONCLUSION: SQLPCV is associated with a decreased likelihood of IUFD-D and an increased rate of dual survivors compared to SLPCV. SQLPCV represents both an anatomical and functional surgical approach to the laser treatment of twin-twin transfusion syndrome.

The role of laser surgery in dissecting the etiology of absent or reverse end-diastolic velocity in the umbilical artery of the donor twin in twin-twin transfusion syndrome.

OBJECTIVE: This study was undertaken to gain insight on the cause of absent or reverse end-diastolic velocity (AREDV) in the umbilical artery (UA) of the donor twin by analysis of individual placental mass and vascular anastomoses in patients with twin-twin transfusion syndrome (TTTS) treated with laser. STUDY DESIGN: TTTS patients who successfully underwent selective laser photocoagulation of communicating vessels (SLPCV), 16 and 26 weeks' gestation, with both twins born alive and complete Doppler and placental data were considered eligible for the study. Doppler examination of the UA was performed before and 24 hours after SLPCV. Abnormal UA Doppler findings were defined as persistent AREDV. Pre- and post-SLPCV UA Doppler results yielded the following 4 groups: (1) normal-normal; (2) normal-abnormal; (3) abnormal-normal; and (4) abnormal-abnormal. The types of vascular anastomoses were categorized during surgery. Individual placental territory (IPT) was defined as individual placental weight divided by total placental weight x 100. RESULTS: There were 132 cases in group 1 and no patients in group 2. AREDV resolved in 78% (28/36) of patients (group 3) and remained unchanged in 22% (8/36) (group 4). The mean IPT-donor in group 4 was significantly smaller than in group 1 (P = .015). Patients with preoperative AREDV (groups 3 and 4) were more likely to have artery-to-artery anastomoses (P = .002). However, AREDV resolved in 57% (16/28) patients without artery-to-artery anastomoses. CONCLUSION: Preoperative AREDV may result from a small IPT, placental vascular anastomoses, or both. AREDV resulting from a small IPT may have a similar cause to that of singletons, and may be inferred by lack of postoperative resolution. Resolution of AREDV after SLPCV implies the presence of an adequate IPT and removal of donor hypotension.

Surgical management of twin reversed arterial perfusion sequence.

OBJECTIVE: The purpose of this study was to review our experience in the management of twin reversed arterial perfusion sequence to derive management recommendations. STUDY DESIGN: All patients with twin reversed arterial perfusion sequence who were seen for consultation between 1993 and 2004 were studied. Criteria for umbilical cord occlusion included abdominal circumference of the twin reversed arterial perfusion fetus that was more than or equal to the pump twin, polyhydramnios (maximum vertical pocket > or = 8 cm), abnormal Doppler studies or hydrops of the pump twin, or monoamniotic twins. Various surgical and access techniques for umbilical cord occlusion were used as they were developed. RESULTS: Seventy-four patients with twin reversed arterial perfusion sequence were studied. Sixty-five patients were considered surgical candidates, of which 51 patients underwent umbilical cord occlusion attempt. The overall perinatal survival for surgical candidates who had umbilical cord occlusion was 65% (33/51 patients) versus 42.9% (6/14 patients) for the surgical candidates who did not undergo umbilical cord occlusion (P = .1). However, perinatal outcomes in surgical patients were significantly better than expectantly treated surgical candidates if the dividing membrane was not disrupted purposely (22/28 patients; 78.5%; P = .02). Surgery within the sac of the twin reversed arterial perfusion fetus was feasible in 23.5% of patients and was associated with no incidence of premature rupture of membranes, with 83% perinatal survival, and with a significantly greater gestational age at delivery (36 weeks). There were no significant differences in perinatal outcome relative to the specific surgical technique that was used. CONCLUSION: Surgical management of twin reversed arterial perfusion sequence is indicated in high-risk patients. The surgical approach and the surgical technique should be tailored to the specific clinical presentation, preferably by performing the surgery within the sac of the twin reversed arterial perfusion sequence fetus and avoiding disruption of the dividing membrane.

Stage-based treatment of twin-twin transfusion syndrome.

OBJECTIVE: The purpose of this study was to compare the outcomes of patients with twin-twin transfusion syndrome who were treated with either serial amniocentesis or selective laser photocoagulation of communicating vessels according to disease severity (stage). STUDY DESIGN: Centers that were experienced in the treatment of twin-twin transfusion syndrome were invited to share stage-based perinatal outcome data. All patients met basic standard sonographic criteria for twin-twin transfusion syndrome (polyhydramnios maximum vertical pocket, > or =8 cm; oligohydramnios maximum vertical pocket, < or =2 cm). Gestational age at first treatment was <27 weeks of gestation. RESULTS: Three centers submitted stage-based data, for a total of 173 patients (serial amniocentesis, 78 patients from all 3 centers) and 95 selective laser photocoagulation of communicating vessels (1 center). The distribution of patients by stage was similar in the two groups. Successful pregnancy outcome (at least 1 surviving infant) was correlated inversely with stage in the serial amniocentesis but not in the selective laser photocoagulation of communicating vessels group and was significantly lower in the serial amniocentesis (66.7%) than in the selective laser photocoagulation of communicating vessels group (83.2%). Neurologic morbidity was related directly to stage in the serial amniocentesis group but not in the selective laser photocoagulation of communicating vessels group and was significantly higher in the serial amniocentesis (24.4%) than in the selective laser photocoagulation of communicating vessels (4.2%) group. Intact neurologic survival (at least 1 surviving infant without neurologic morbidity) was significantly lower in the serial amniocentesis group than in the selective laser photocoagulation of communicating vessel group (51.3% vs 78.9%), particularly in stage III and stage IV (23.5% vs 72.7% in stage IV). Patients who were treated with selective laser photocoagulation of communicating vessels were 2.4 times more likely to have at least one survivor than those treated with serial amniocentesis. CONCLUSION: Our study suggests a relationship between perinatal morbidity and mortality rates and stage in serial amniocentesis but not in selective laser photocoagulation of communicating vessel-treated twin-twin transfusion syndrome patients. These findings could be used to tailor the treatment of twin-twin transfusion syndrome. A clinical trial to confirm these results is being organized by our research groups.

Placental types and twin-twin transfusion syndrome.

OBJECTIVE: The purpose of this study was to assess the value of a proposed classification of monochorionic placenta in reference to twin-twin transfusion syndrome. STUDY DESIGN: The placentas from laser-treated patients with twin-twin transfusion syndrome and from uncomplicated monochorionic pregnancies that were delivered between January 1997 and December 2000 were included in the study. Placentas were classified as type A (no anastomoses), type B (only deep anastomoses), type C (only superficial anastomoses), and type D (deep and superficial anastomoses). The number and type of anastomoses were documented in each placental type. The severity of twin-twin transfusion syndrome was assessed in stages, as previously described. The relationship between placental types and the development and severity of twin-twin transfusion syndrome was determined. RESULTS: One hundred thirty-one placentas were examined. Twin-twin transfusion syndrome developed in 0% (0/4 placentas) of type A, in 100% (85/85 placentas) of type B, in 5.6% (1/18 placentas) of type C, and in 79.17% (19/24 placentas) of type D placentas. An average of 4.17 (range, 1-11) vascular anastomoses was found. The mean number of superficial anastomoses was not different between patients with twin-twin transfusion syndrome and patients with no twin-twin transfusion syndrome (1.6 vs 1.71, respectively; P =.69, Student t test). The presence or absence of superficial anastomoses was not associated with differences in the severity of twin-twin transfusion syndrome. CONCLUSION: This classification represents a practical approach to the surgical pathologic assessment of vascular anastomoses in monochorionic placentas, with a strong clinical correlation. It also allows for the clarification of the relationship between superficial anastomoses and twin-twin transfusion syndrome.