Anticipating twin–twin transfusion syndrome in monochorionic twin pregnancy. Is there a role for nuchal translucency and ductus venosus blood flow evaluation at 11–14 weeks?

A Study of Multiple Deliveries in Portugal: Indications of an Iberian Peninsula Pattern

Information on multiple deliveries with regard to Portugal is scarce. Based on data provided by the Portuguese Institute of Statistics (INE), the rates for double and triple deliveries were calculated since 1930. The results obtained show for twins a uniform temporal pattern up to the 1970s. At this time rates decreased, but later they gradually recovered, reaching their maximum level in 2010. For triplets, the highest rates occurred between 1999 and 2002. For the period 1988–2011, the rates of multiple deliveries were related to a set of variables recorded in the INE database on live births. Significant differences (p < .001) between simple and multiple deliveries were obtained for maternal age, parity and marital status. Considering the year when the delivery occurred, significant differences (p < .001) persisted for maternal age regardless of the year. For the type of mating, significance was consistently found since the year 2002 (either by using the marital or the cohabitation criteria), and for parity since 2003. With regard to territorial variation, throughout seven periods between 1930 and 2011, the rates among the 20 administrative Portuguese territories, including the two insular districts of Açores and Madeira, were mostly stable for twinning rates, with a minimum level in 1970–1989. Regarding triplets, the greatest inter-district variation was found after 1980. The results of the Portuguese study on multiple deliveries are interpreted in the context of the Iberian Peninsula based on findings reported for Spain.

The Role of Ultrasound in Multiple Pregnancy

The advances in reproductive technologies have changed the demographics of multifetal pregnancies. In the first trimester, ultrasound allows to diagnose the number of multiples, chorionicity and amnionicity, the presence or absence of nuchal translucency, early growth discordance, severe malformations and the origin of activities and contacts between multiples. In the second and third trimester, the opportunity to examine the cervix by transvaginal ultrasound should not be missed to detect the risk of premature delivery. Ultrasound is essential for the early grading and treatment of twin-to-twin transfusion syndrome (TTTS), the diagnosis of malformations and growth disturbances. Doppler velocimetry has proven to be able to reduce perinatal mortality in twin pregnancies. Finally, ultrasound is used for the detection of the position of multiples and the decision of the optimal route of delivery. This is of main importance in delayed interval delivery and expectant management of multifetal pregnancies and early cervical dilatation.

Ductus Venosus: A Love Story of 14 Years

Ductus venosus is a tiny vessel with a central role in fetal circulation. Combining B-mode with color and pulsed Doppler is feasible to identify this vessel and evaluate the blood flow waveform at 11 to 13 weeks. The higher prevalence of abnormal A-wave in fetuses with abnormal karyotype and/or cardiac defects turned DV evaluation into a useful marker for chromosomal abnormalities and cardiopathies. Even when combined with nuchal translucency (NT) or biochemical markers, DV blood flow evaluation contributes to an increase in sensitivity and reduces false-positive rate. Abnormal ductal flow is also related to a worse fetal and perinatal outcome. In monochorionic twin pregnancies, in addition to NT measurement at 11 to 14 weeks, the Doppler assessment of DV blood flow increases relevantly the performance of screening for those at higher risk of developing twin-to-twin transfusion syndrome. This story of 14 years surely contributed to change the way first trimester screening is being implemented.

Screening for twin-twin transfusion syndrome at 11-14 weeks of pregnancy: the key role of ductus venosus blood flow assessment

OBJECTIVES

A discrepancy in crown-rump length (CRL) and/or nuchal translucency thickness (NT) between monochorionic twins has been found to be associated with an increased risk of twin-twin transfusion syndrome (TTTS). As one of the most plausible mechanisms for increased NT is hemodynamic imbalance and cardiac dysfunction, indirectly manifested by abnormal blood flow in the ductus venosus (DV), we aimed to clarify the role of DV blood flow assessment in identifying those monochorionic twins more prone to develop TTTS.

METHODS

We present 99 cases of monochorionic diamniotic twin pregnancies in which CRL, NT and DV blood flow were evaluated at 11-14 weeks' gestation.

RESULTS

Discrepant values of CRL were not predictive of TTTS development. Intertwin NT discrepancy >or= 0.6 mm had a sensitivity of 50.0% and a specificity of 92.0%. The presence of at least one abnormal blood flow waveform in the DV was associated with a relative risk for developing TTTS of 11.86 (95% CI, 3.05-57.45), with a sensitivity of 75.0% and a specificity of 92.0%. The combination of abnormal DV blood flow with NT discrepancy >or= 0.6 mm yielded a relative risk for the development of TTTS of 21 (95% CI, 5.47-98.33).

CONCLUSIONS

Both intertwin discrepancy in NT and abnormal flow in the DV in monochorionic twins may represent early manifestations of hemodynamic imbalance between donor and recipient. In these pregnancies, in addition to NT measurement at 11-14 weeks, the Doppler assessment of DV blood flow significantly increases the performance of screening for those at risk of developing TTTS.

Search for hemodynamic compromise at 11–14 weeks in monochorionic twin pregnancy: Is abnormal flow in the ductus venosus predictive of twin–twin transfusion syndrome?

BACKGROUND AND OBJECTIVES

Twin-twin transfusion syndrome is a devastating complication of monochorionic twin pregnancies. The presence of increased nuchal translucency thickness (NT) in one of the monochorionic twins has been associated with an increased risk of developing this syndrome. One of the most plausible mechanisms for increased nuchal translucency is heart failure, indirectly manifested by abnormal blood flow in the ductus venosus. We aimed to clarify the pathophysiology of increased NT found more frequently in monochorionic twins prone to develop twin-twin transfusion syndrome.

DESIGN

We present 50 cases of monochorionic twin pregnancies in which nuchal translucency thickness was measured and ductus venosus blood flow evaluation was performed at 11-14 weeks of gestation.

RESULTS

Whenever the fetuses of a twin pregnancy were found to have discrepant nuchal translucency thickness measurements and abnormal flow in the ductus venosus was found in the fetus with increased nuchal translucency thickness, twin-twin transfusion syndrome eventually developed. Progression to twin-to-twin transfusion syndrome was not observed in the twins displaying no intertwin difference in nuchal translucency thickness measurements and it was not observed in those with discrepant nuchal translucency thickness but normal flow in the ductus venosus of both fetuses. In the two cases which developed twin-to-twin transfusion syndrome, fetoscopic laser coagulation of the vascular anastomoses was successfully carried out at 18 weeks and normalization of the venous return was recorded.

CONCLUSIONS

Both increased nuchal translucency and abnormal flow in the ductus venosus in monochorionic twins may be early manifestations of haemodynamic imbalance between donor and recipient. The combined evaluation of both parameters in monochorionic twin pregnancies may constitute an effective method for identifying those at risk of developing twin-to-twin transfusion syndrome.

Ductus venosus Doppler velocimetry in the first trimester: a new finding

OBJECTIVES

To establish reference curves for ductus venosus blood flow velocities during the first trimester and compare them with previously published curves.

METHODS

This was a cross-sectional and retrospective study performed between January 1998 and January 2003. The following inclusion criteria were used: singleton pregnancy, velocity measurements taken when the crown-rump length (CRL) was between 34 and 84 mm, absence of fetal anomalies, full-term pregnancy and newborn birth weight appropriate for gestational age. The following variables of the ductus venosus were measured: peak velocity during ventricular systole (S-wave) and diastole (D-wave), nadir during atrial contraction in late diastole (A-wave), time-averaged maximum velocity (TAMXV) and pulsatility index for veins (PIV).

RESULTS

A total of 843 fetuses were included. The mean CRL was 62 (range, 34-84) mm. The S-wave, D-wave, TAMXV and PIV were normally distributed, and logarithmic transformation was performed to achieve a normal distribution for the A-wave. S-wave, D-wave and A-wave and TAMXV increased with CRL. PIV increased up to a CRL of 63 mm and decreased thereafter. Regression analysis revealed a significant quadratic relationship between PIV and CRL.

CONCLUSIONS

S-wave, D-wave, A-wave velocities and TAMXV in the ductus venosus increase with CRL between 34 and 84 mm. The reference range for PIV has a biphasic pattern, with an initial non-significant increase up to a CRL of 63 mm and a fall thereafter.

Timely diagnosis of twin-to-twin transfusion syndrome in monochorionic twin pregnancies by biweekly sonography combined with patient instruction to report onset of symptoms

OBJECTIVES

To assess the value of serial ultrasound examinations together with patient instructions to report the onset of symptoms in achieving timely detection of twin-to-twin transfusion syndrome (TTTS) in a cohort of monochorionic diamniotic twin pregnancies, and to evaluate sonographic TTTS predictors.

METHODS

Timely detection of TTTS was defined as diagnosis before severe complications of TTTS occurred, such as preterm prelabor rupture of membranes, very preterm delivery (24-32 weeks of pregnancy), fetal hydrops, or intrauterine fetal death. During a 2-year period, a prospective series of 23 monochorionic twin pregnancies was monitored from the first trimester until delivery. At least every 2 weeks we performed ultrasound and Doppler measurements (nuchal translucency thickness, presence of membrane folding, estimated fetal weight, deepest vertical pocket, bladder filling, and Doppler waveforms of the umbilical artery, ductus venosus and umbilical vein). Measurements of TTTS cases were compared with those of non-TTTS cases matched for gestational age. Furthermore, patients were informed about the symptoms caused by TTTS, and instructed to consult us immediately in case of rapidly increasing abdominal size or premature contractions.

RESULTS

In all four TTTS cases, the diagnosis was timely. At the time of diagnosis, one case was at Quintero Stage 1, two at Quintero Stage 2, and one at Quintero Stage 3. Two of the TTTS cases became apparent after the patients' feeling of rapidly increasing girth. The identification of TTTS predictors was successful with respect to one parameter: isolated polyhydramnios in one sac, without oligohydramnios in the other, preceded the ultimate diagnosis of TTTS in two of the four TTTS cases. All other ultrasound measurements of TTTS cases, prior to the diagnosis of TTTS, were within the range of measurements of non-TTTS cases.

CONCLUSION

Biweekly ultrasound examinations, with special attention to the amniotic fluid compartments of both fetuses, combined with detailed patient instructions to report the onset of symptoms resulted in timely diagnosis of all TTTS cases and appears to be a safe program for monitoring monochorionic twin pregnancies.

Hypothesis: The Placental ‘Steal’ Phenomenon – A Possible Hazard of Amnioreduction

The twin-twin transfusion syndrome (TTTS) complicates approximately 15% of monochorionic twin pregnancies. Severe TTTS is associated with poor neonatal outcome and a relatively high rate of neurological abnormalities. Some studies have suggested this outcome to be more severe in cases treated by amnioreduction. In this paper we present a hypothesis that radical amnioreduction performed after 24 weeks of gestation might cause a shift of blood from the fetus into the placenta. This could explain some of the severe neurological outcomes, such as hypoxic ischemic brain damage, seen in these cases.

The clinical evaluation and pregnancy outcome of euploid fetuses with increased nuchal translucency

This review aims to address the systematic work-up and counseling throughout pregnancies with increased nuchal translucency (NT) in euploid fetuses. Original articles from peer-reviewed English-language journals between 1997 and 2003 were studied. They all included descriptions of pregnancy outcomes of euploid fetuses with increased NT. Eleven studies reporting on the pregnancy outcome of 2128 euploid fetuses with increased NT (> or = 3 mm or > or = 95 centile) were retrieved by our literature search. A statistical analysis was conducted for assessing the consistency of effects across studies. The chi2 tests were applied to verify the homogeneity of the results from different series. A significant difference was found between the studies even when the results were analyzed separately according to various NT cutoff levels (i.e. > or = 3 mm, > or = 3.5-4 mm, and > or = 95 centile). These discrepancies suggest that those studies are significantly different and therefore, cannot be combined for meta-analysis. Of all the reported series, 2.2-10.6% of the fetuses have miscarried and 0.5-15.8% ended in perinatal death. There was an overall rate of 0.5-12.7% neurodevelopmental problems, and 2.1-7.6% of the malformations which were undiagnosed before birth. Importantly, 70-90% fetuses had normal outcomes. A detailed two-step anomaly scan including midgestation fetal echocardiography should be part of perinatal management of pregnancies with increased fetal NT. Data on relevant family history and persistence of nuchal edema provide additional relevant information for planning pregnancy management.