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• W1576897035 abstract "Twins have a more complicated intrauterine journey than do singletons. Also, their management is complicated because the interests of both twins have to be taken into account at all times. Moreover, in monochorionic pairs, there is the added risk of the shared circulation that can cause transfusion imbalances and makes their wellbeing interrelated. Due to artificial reproductive technologies, we now encounter more twin pregnancies than ever before. Most twin pregnancies resulting from assisted conception are dizygotic and thus dichorionic. Nevertheless, the risk of monozygotic cleavage is increased after assisted conception and these monozygotic twins are more likely to have a monochorionic placenta1. As such, about 1 in 20 twin pregnancies following assisted conception will be monochorionic. Ultrasound plays a key role in the surveillance of twin pregnancies. The first-trimester scan is of paramount importance for determination of chorionicity, risk assessment for chromosomal anomalies and detection of major structural anomalies. Simply diagnosing a twin pregnancy is insufficient; chorionicity should always be specified and it is of paramount importance to identify the high-risk monochorionic twin pregnancy early. There is general consensus that monochorionic twin pregnancies should benefit from fortnightly scans to detect twin–twin transfusion syndrome (TTTS); this complicates 1 in 10 monochorionic pairs, mostly in the previable period between 16 and 26 weeks, and is diagnosed by measuring the deepest vertical amniotic fluid pockets. Timely detection of TTTS is necessary because invasive fetal therapy may salvage one or both twins2. Additionally, expert opinion recommends the inclusion of middle cerebral artery (MCA) peak systolic velocities (PSV) in the routine follow-up of monochorionic twins, in order to detect twin anemia-polycythemia sequence (TAPS). This condition occurs in 1 in 25 monochorionic twin pairs, mostly in the viable period after 26 weeks, and is diagnosed by measuring the MCA-PSV (< 0.8 in the recipient and > 1.5 multiples of the median in the donor). Timely detection of TAPS and intrauterine treatment or elective preterm birth may prevent a number of late intrauterine fetal deaths which presumably would have remained unexplained3, 4. In addition to identifying complications of the shared circulation, the purpose of sonographic follow-up is to detect poor growth and structural anomalies, both of which occur more commonly in monochorionic twin pregnancies. Dichorionic twin pregnancies are usually scanned every 4 weeks, primarily to detect poor growth and structural anomalies. The convenient aspect of scanning twin pregnancies is that one essentially looks for discordance (in growth, Doppler recordings, amniotic fluid and anatomy) and the presence of two fetuses means that each one can serve as the other's control. The downsides of scanning twins are that it is time-consuming and, more often than not, visualization is hampered by intrauterine crowding. As in singleton pregnancies, cervical length measurement is the most important predictor of preterm birth in twins and a cervical length < 25 mm is useful to decide whether or not a symptomatic patient should receive steroids and tocolysis5. Since there is no proven useful intervention that prolongs pregnancy or alters outcome, routine cervical length measurement at mid-gestation is not as yet recommended. From 32 weeks onward, biophysical profile score and fortnightly growth checks may help to confirm fetal wellbeing and determine the optimal time of birth in monochorionic as well as dichorionic pregnancies. Evidence as well as expert opinion suggest that uncomplicated monochorionic twin pregnancies are best delivered at 36–37 weeks and uncomplicated dichorionic twins at 37–38 weeks because, at these time points, intrauterine mortality of twin pregnancies equals that of post-term singleton pregnancies6-8. Finally, during the second stage of labor and after delivery of the first twin, the availability of a bedside scanning machine is practical to determine the position of the second twin and to assist with internal or external version if necessary. So, from the first trimester up to the time of birth itself, ultrasound examination plays an indispensable role in fetal surveillance and in optimizing the outcome of twin pregnancies. Just as twin pregnancies keep many obstetricians busy, so it is fitting that a substantial proportion of this month's journal should be dedicated to papers dealing with their management. Three papers are from the Southwest Thames Obstetric Research Collaborative (STORK) multiple pregnancy cohort, which comprises more than 2000 twin pregnancies that have been followed from the first trimester over the past 10 years9-11. The first paper9 demonstrates that, in the absence of structural or chromosomal anomalies, the crown–rump length (CRL) difference is only a weak predictor of mortality; the main predictor of adverse pregnancy outcome is whether the twins share a single placenta, thereby underlining the importance of correctly determining chorionicity in the first trimester. Most previous series that observed an association between CRL discordance of > 10–11% with mortality prior to 24 weeks did not exclude anomalies in their analysis and the excess early loss in the discordant group is probably explained largely by the presence of anomalies. As such, Harper and coworkers, in a retrospective cohort study also published in the current issue12, report higher rates of fetal loss prior to 20 weeks and of structural anomalies when CRL discordance > 11%. However, they did not ascertain the presence of anomalies in the pregnancies with early demise, and it is likely that, had this correction been made, the association would have been lost. Both series9, 12 clearly show CRL discordance not to be a particularly good predictor of death in twin pregnancy. Indeed, in twin pregnancies, miscarriage and preterm birth are the most common causes of death, and differences in CRL are not expected to predict these outcomes. Furthermore, fetal positioning may prevent accurate measurement of CRL and thus assessment of true discordance. On the other hand, the results from these two series do not imply that large differences in CRL do not matter and can be ignored safely. As rightly proposed by Harper et al.12, discordant twins deserve detailed follow-up scans, since most anomalies will not be visible in the first trimester. Only in the absence of anomalies can parents be reassured that the risk of death is probably not much higher than that for pregnancies in which both twins start with similar CRL. In dichorionic twins a difference in CRL may simply reflect differences in genetic growth potential. However, monochorionic twins have the same genetic constitution and an early size discrepancy can thus never be entirely normal. Early-onset discordant growth is usually a manifestation of unequal placental sharing or an early transfusion imbalance, or more rarely a discordant genetic or chromosomal syndrome. In fact, several studies13-15 have shown an increased risk of early fetal loss and growth discordance in monochorionic pregnancies with discordant CRL. A second paper from the STORK cohort10 highlights the increased risks of monochorionic compared with dichorionic twin pregnancy, with a 10-fold higher loss rate from 14 to 24 weeks and still a three-fold higher loss rate after 24 weeks. Additionally, an encouraging finding is that loss prior to 24 weeks has decreased significantly over the past 10 years, from 8.9% in the first to 4.9% in the second 5-year periods, which suggests that increased surveillance and adequate treatment by invasive prenatal surgery are starting to pay off. Unfortunately, no such improvement was observed after 24 weeks, with loss rates of 3.6% and 2.3% during the first and second 5-year periods, respectively. Late intrauterine demise is particularly regrettable because the neonatal care unit becomes a viable alternative to the monochorionic placenta. It would be interesting to examine if routine measurement of the MCA-PSV to detect TAPS decreases the number of late deaths, although this would be difficult to assess as the risk of death is considerably lower after 24 weeks. The third STORK series published in this issue11 proposes a birth-weight discordance of > 25% to be the best cut-off to predict perinatal loss. This differs from the recent ESPRiT cohort, that included neonatal morbidity as well as mortality and corrected for gestational age at birth, and which proposed 18% as the optimal threshold to identify growth-discordant twins at risk for adverse outcome16. Moreover, in contrast to the STORK data, the ESPRiT cohort clearly demonstrated an increased risk of adverse outcome in discordant monochorionic twin pregnancies as compared to their dichorionic counterparts. In fact, adverse perinatal outcome of growth-discordant dichorionic twin pregnancies was similar to that of concordant monochorionic twin pairs. A strength of the STORK cohort is that it also demonstrated estimated fetal weight discordance of > 25% to be the best predictor of perinatal mortality. All series concur that growth discordance is a better predictor than is being small-for-dates. In monochorionic twins in particular, growth discordance in the absence of growth restriction confers an added risk of perinatal morbidity17, which supports the concept that discordant growth in monochorionic twins should always be considered as pathological, even if both grow appropriately. It seems prudent, once a discordance of 20% is reached, to check for additional signs of poor growth, such as abnormal Doppler or amniotic fluid volumes. In dichorionic twins, like in singletons, demise of one fetus is usually predicted by a progressive worsening of Doppler studies and biophysical profile score. In growth-discordant monochorionic twins diagnosed in the first half of pregnancy, demise is often difficult to predict because of the influence of the shared circulation on Doppler parameters. At present, severe oligohydramnios seems to be the best predictor of demise in discordant monochorionic twin pairs with abnormal umbilical artery Dopplers in the smaller twin18. Nevertheless, better parameters are necessary to distinguish the growth-discordant monochorionic twin at risk of demise from the discordant pair that will do well until birth. The topic of the diagnosis of growth restriction in twin pregnancy brings us nicely to the study by Odibo and coworkers19, which advocates the use of twin-specific growth charts as being better at predicting intrauterine demise. The use of twin-specific growth charts has so far failed to gain widespread acceptance, mainly because of the fear that they may create a false sense of security that being small is normal for a twin pregnancy. Interestingly, up to about 36 weeks, the 10th percentile is actually higher in twins, whereas after 36 weeks it becomes progressively lower than in singletons. This apparent overgrowth in twins prior to 32 weeks was also suggested by an earlier publication20. The same paper also documented a progressive decrease in growth velocity from 34 weeks onwards, so that at 38 weeks the average twin will be growth restricted according to singleton standards20. It will be interesting to see how well the twin charts perform in comparison with or in addition to growth discordance to predict adverse outcome. The advantage of using growth discordance is that it is independent of the kind of growth chart used. Also, the area under the curve of birth-weight discordance to predict perinatal mortality (0.72) seems better than that of the customized twin charts to predict intrauterine demise (0.55). Further studies are necessary to compare the accuracy of growth assessed by twin-specific charts to that of birth-weight discordance in the prediction of pregnancy outcome. The paper by DeKoninck et al.21 presents a monochorionic twin-specific reference chart for deepest vertical pocket measurements. The purpose of the paper is not so much to recommend this chart for use in clinical practice but rather to provide a scientific basis for the gestational-age-specific Eurofoetus cut-off to define polyhydramnios in TTTS (> 8 cm prior to 20 weeks, > 10 cm after 20 weeks). In contrast, across the Atlantic, a fixed cut-off of > 8 cm is used throughout gestation. The use of the more stringent European cut-off is especially relevant in early-stage TTTS. Up to a third of cases classified as Stage I TTTS according to the USA criteria would not be considered as TTTS in Europe and would therefore not undergo fetoscopic laser surgery22. The last twin paper of this issue is by van den Bos and coworkers23, who report 67% survival and 12% neonatal morbidity in a series of 131 selective reductions in complicated monochorionic twin pregnancies. They used several techniques, including laser or umbilical cord coagulation as well as intrafetal laser or radiofrequency ablation. Survival was significantly lower if the procedure was performed prior to 18 weeks. Two previous large series24, 25, using only bipolar coagulation, also reported higher loss rates when this was performed prior to 18 weeks, due to increased fetal demise in one24 and increased miscarriage rates in the other25. In the current series, the increased loss with early intervention did not seem to be related to preterm premature rupture of membranes (PPROM). Also, in this series, cord coagulations prior to 18 weeks were performed with a 1-mm embryoscope, which is significantly smaller than the 3.3-mm entry used to perform bipolar cord coagulation. It is probable that, in this series, the higher loss rate associated with early reductions was due either to more severe disease, necessitating early reduction, or to a reduced efficiency of laser coagulation to achieve complete arrest of flow. Regardless of the exact mechanism involved, it is generally recommended that selective reduction is best delayed (if possible) until after 18 weeks, the exception being in the case of twin reversed arterial perfusion (TRAP) sequence, when treatment is generally performed early. As for all invasive procedures, PPROM, miscarriage and severe preterm birth were an important cause of perinatal death and morbidity. PPROM is definitely the Achilles' heel of every invasive procedure and less invasive treatment options should be explored. As such, radiofrequency ablation may seem a better technique due to its smaller (1.4 mm) instrument size. However, the largest series on this topic26 reported a significantly lower survival rate with radiofrequency ablation (70%) compared to bipolar coagulation (88%), especially in the management of twins with discordant anomalies (33% vs 85%). Although radiofrequency ablation is technically a simple technique and comparable to chorionic villus sampling, it appears that, for indications other than TRAP sequence, the circulatory confinement is not as reliable as that produced by bipolar cord coagulation, thereby increasing the risk of double intrauterine demise. In summary, ultrasound plays an indispensable role in the surveillance of twin pregnancies from the first trimester until delivery. Monochorionic twins have the highest risk of death, especially prior to viability, and dedicated monitoring as well as access to invasive prenatal therapy appear to have reduced early fetal loss rates by increasing survival in cases of TTTS and severe early discordant growth. Expert opinion recommends the inclusion of MCA-PSV measurements in the routine follow-up of monochorionic twins in the latter half of pregnancy, which may prevent some of the late, previously unexplained, stillbirths due to TAPS. It is also expected that better sonographic predictors will become available to identify those growth-discordant monochorionic pregnancies at increased risk of intrauterine demise. These cases may be offered prenatal therapy to protect the appropriately growing twin against the risks of perimortem exsanguination. Unfortunately, all prenatal intervention entails a high risk of PPROM, miscarriage or severe preterm birth. Therefore, the development and implementation of non-invasive methods, such as high-intensity focused ultrasound, would be a tremendous improvement. Since miscarriage and severe preterm birth are the most common cause of death in twins in general, an effective intervention is eagerly awaited so that routine cervical length measurement can truly reduce overall perinatal mortality in twins. Finally, no matter how gratifying and fascinating it is to look after twin pregnancies, it is hoped that more widespread use of single embryo transfer by our fertility colleagues will contain the current twin pandemic." @default.
• W1576897035 created "2016-06-24" @default.
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• W1576897035 date "2013-05-28" @default.
• W1576897035 modified "2023-09-25" @default.
• W1576897035 title "Management of twin pregnancies: where do we go from here?" @default.
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• W1576897035 cites W1966474099 @default.
• W1576897035 cites W1973327553 @default.
• W1576897035 cites W1974345749 @default.
• W1576897035 cites W1989381360 @default.
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• W1576897035 cites W2038964647 @default.
• W1576897035 cites W2051253134 @default.
• W1576897035 cites W2072318318 @default.
• W1576897035 cites W2125418089 @default.
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