• 1.
  

  a) T b) F c) F d) F e) T

Ultrasound determination of chorionicity is best achieved in the first trimester of pregnancy using the Lambda (λ) and T signs. ‘λ’ or ‘twin peak’ sign refers to the classical appearance of the inter-twin membrane at its placental attachment. In cases of dichorionic placentation, the presence of a triangular tissue projection extending from the base of the inter-twin membrane gives the latter a characteristic appearance of the Greek letter ‘λ’. This projection is produced by extension of chorionic villi into the inter-chorionic space of the twin membrane at the point where it encounters the chorion and placenta of the co-twin. In cases of monochorionic placentation, the lack of tissue projection into the inter-twin membrane prevents the formation of λ sign and the inter-twin membrane inserts perpendicularly into the placental plate. These two signs are mutually exclusive in twins with a single placental mass. Although highly predictive of dichorionic placentation in the first trimester of pregnancy, the λ-sign gradually disappears during the second trimester of pregnancy, limiting its predictive accuracy.

• 2.
  

  a) F b) F c) F d) T e) T

Because no clinically validated twin formulae for fetal growth in the first trimester are available, it has been questioned if singleton CRL charts should be used to date twin pregnancies. Martins et al. showed no significant difference between CRLs of twins and singletons between 7 and 10 weeks of gestation, whereas Wisser et al. showed a maximum discrepancy of 1.6 days between twins and singletons. When comparing the CRL of the smaller and larger twin with that of singleton pregnancies, Salomon et al. and Chaudhuri et al. reported that the CRL of the smaller twin was closest to the actual gestational age, whereas Dias et al. found no significant difference between both smaller and mean CRL in twins with that of singleton gestations. A difference in twin CRLs is a common finding in twin gestations and it is not related to chorionicity and seems to reflect a physiological variation rather than a pathological condition. A policy of dating twin pregnancy according to the smaller CRL would minimise parental anxiety about apparent reduced growth in the first trimester. Reduced fetal growth, however, might be linked with chromosomal or structural abnormalities, and it is difficult to be confident whether the small twin is normally or pathologically small during the early stages of pregnancy. A policy of dating by using the larger CRL may be more effective because it is relatively infrequent for a twin to be pathologically large. This policy, however, may exaggerate the relative smallness of the other twin and may increase the parental anxiety. Dating by the mean CRL may be a reasonable alternative, limiting the parental anxiety without compromising accuracy.

• 3.
  

  a) F b) T c) F d) T e) F

A variety protocols for labelling twins have been used by different units and even individual operators. These include fetal presentation, sac position, and placental site. The lack of consistency in labelling predisposes to errors in twin identification. Identifying each fetus by the position of its placenta is of limited value as placental positions change with advancing gestation; however, this technique cannot be used with twin pregnancies where the placenta is either monochorionic or fused dichorionic. Antenatal determination of fetal sex is difficult in early pregnancy and is of no value in same-sex twin pregnancies. The position of each twin relative to the maternal cervix is often used to label twin pregnancies; however, the position of either fetus relative to the cervix can change considerably, especially in early pregnancy, thus limiting the clinical applicability of this method. A recent study proposed a consistent method of twin identification throughout pregnancy based on the relationship between the gestational sac and maternal cervix. In this study, at the 11–14-week ultrasound assessment, the fetus contained in the gestational sac closest to the internal orifice was designated as Twin 1. The relative orientation of the fetuses to each other was then defined as either lateral (left/right) or vertical (top/bottom). Lateral fetal orientation was associated with an inter-twin membrane running vertically along the longitudinal axis of the uterus, whereas vertical fetal orientation was associated with an inter-twin membrane running horizontally across the longitudinal axis of the uterus. The reproducibility of this method is likely to be good because position of the gestational sac relative to the cervix remains constant throughout pregnancy, allowing an objective differentiation between the two fetuses. Interestingly, 16% of the twins changed presentation when the scan orientation was compared with the birth order, and this change in twin order was significantly higher for twins delivered by caesarean section compared with those delivered vaginally.

• 4.
  

  a) F b) T c) F d) F e) T

Discordance in CRL is a factor commonly taken into consideration in counselling parents about the outcome of the pregnancy, and different thresholds have been investigated. The role of CRL discordance in predicting the outcome in twin pregnancies, however, is still conflicting, with different studies reporting contrasting results. The largest study exploring the role of CRL discrepancy detected at the time of the 11–14 weeks scan shows that inter-twin CRL discordance is independent of chorionicity, and is not a particularly good predictor of early fetal loss, perinatal loss, birth weight discordance, or preterm birth once chromosomal or structural abnormalities and twin-to-twin transfusion syndrome are excluded. In this study, chorionicity, abnormal nuchal translucency, nuchal translucency discordance and small CRL were not independently associated with the occurrence of an adverse fetal outcome. Although surprising, this finding can be explained on the basis of the peculiar pathophysiology of fetal growth in twin pregnancies. The uterine milieu is usually able to supply the metabolic demands of both twins during the second and early third trimester, until about 28–32 weeks, after which twin growth usually diverges from that of singletons. Some evidence shows that even in cases of severe discordant growth, the utero-placental unit supplies 50–75% more than that for the average singleton gestation. This suggests that delayed growth in one twin during the first trimester is unlikely to occur as the result of dysfunction in the utero-placental unit.

• 5.
  

  a) T b) F c) T d) F e) F

Diagnosis of TTTS is usually made in the second trimester of pregnancy, and the Quintero staging system is widely used. Several investigators have attempted to correlate first-trimester ultrasound findings, such as crown–rump length and nuchal translucency discrepancy with the early prediction of TTTS. Lewi et al. found that discrepancy in CRL and amniotic fluid volume increased the risk of developing TTTS later in gestation, but other studies have failed to corroborate this association. Sebire et al. were the first to investigate the role of nuchal translucency in predicting TTTS, and found that the presence of a nuchal translucency above the 95th centile for singleton pregnancy had a positive predictive value of 38% and a negative predictive value of 91% for future development of TTTS. Kagan et al. found that a discordance in nuchal translucency of 20% of more had a detection rate of 52% for severe TTTS for a false positive rate of 20%. Several investigators have reported similar results although others have failed to find a strong association between TTTS and abnormal nuchal translucency. Matias et al. reported that an abnormal flow in the ductus venosus in at least one fetus between 11 and 14 weeks of gestation resulted in a relative risk of 11 for the developing of TTTS, with a sensitivity of 75% and a specificity of 92%, and that a combination of inter-twin nuchal translucency discordance 0.6 mm or greater, and an abnormal flow in the ductus venosus increased this relative risk up to 21. Maiz et al. found that the occurrence of TTTS increased from 15% to 30% if a reversed a-wave was present in one of the fetuses and reduced to 10% if the ductus venosus flow was normal in both fetuses at 11–13 weeks. A recent study found that a discrepancy in CRL of 0.71 mm or more at 11–14 weeks had a sensitivity of 92% and specificity 76% for the detection of this condition. It is biologically plausible that the imbalance in placental sharing for selective intrauterine growth restriction is evident from early pregnancy, and is manifested as discrepant CRL measurements. In contrast, the vascular imbalances characteristic of TTTS may not cause discrepant early growth, although the haemodynamic compromise of the recipient may manifest as increased nuchal translucency, nuchal translucency discordance, or abnormal flow pattern in the ductus venosus. The transient nature of nuchal translucency enlargement, however, precludes its reliability in predicting TTTS, thus limiting its use as a screening test.

• 6.
  

  a) T b) T c) F d) T e) F

Although it remains debatable, first-trimester loss is not known to result in an adverse outcome for the co-twin. However, sIUFD in the second and third trimester can be associated with substantial risk in the co-twin. Owing to shared placental circulation, monochorionic pregnancies are at increased risk of ‘back-bleed’ from the surviving fetus into the dead fetus. Monochorionic twins had five times higher odds of co-twin demise after sIUFD compared with dichorionic twins (OR 5.24, 95% CI 1.75 to 15.7; P < 0.05). The risk of fetal death in dichorionic pregnancies with selective IUGR approximates that of IUGR singleton pregnancies; therefore, it has been recommended that IUGR in dichorionic pregnancy be managed similarly to singleton pregnancies. Type II selective IUGR (persistent absent or reversed end-diastolic flow in the umbilical artery Doppler) has been associated with a severe fetal deterioration rate of up to 90% and carries the worst prognosis compared with type I and III. A recent systematic review showed no significant difference between the preterm delivery rate of monochorionic and dichorionic survivors (odds ratio 1.1, 95%; CI 0.34 to 3.51; P = 0.9).

• 7.
  

  a) F b) T c) F d) T e) F

A systematic review has shown that the rate of neurodevelopmental impairment after single IUFD was 26% in monochorionic pregnancies and 2% in dichorionic pregnancies, leading to an odds ratio of 4.81 (95% CI 1.39 to 16.6; P < 0.05), which is over four times higher risk. It has been shown that neonatal survivors have less brain abnormality when their twin suffered sIUFD after vascular occlusion treatment than in neonatal survivors whose twin suffered sIUFD spontaneously; this supports the concept that vascular occlusion treatment protects the survivor twin from neurological morbidity. For dichorionic pregnancies, a conservative approach is advocated, and delivery is not indicated before 38 weeks gestation unless there is another obstetric indication. For monochorionic pregnancies, a conservative approach should be implemented when sIUFD occurs before 34 weeks and it is thought that ischaemic brain damage in the survivor occurs during or soon after the death of the co-twin, thus immediate delivery would only add to complications of prematurity. Studies have shown that cavitating lesions in the brain of a survivor twin appear two or more weeks after sIUFD; therefore, a MRI brain should be carried out at least 3 weeks after sIUFD. Risk of pre-eclampsia and other hypertensive disorders are increased after sIUFD; thus, these women need regular blood-pressure monitoring and urinalysis for proteinuria. In addition, there is a theoretical risk of disseminated intravascular coagulation; therefore, monitoring of maternal coagulation and platelets is advocated.

• 8.
  

  a) F b) F c) T d) F e) F

The symptoms of discordant amniotic fluid volume and discordant growth may well be caused by an unequally shared placenta. This may already be suspected when a discordant CRL is seen in the first trimester. The relatively large amount of fluid in the sac of the larger twin, however, does not typically fit this picture, and as the Quintero staging with its cut-off of 8 cm to define polyhydramnios was described for pregnancies of at least 16 weeks, an early TTTS could well present like this. Officially, Quintero Stage I warrants a deepest pocket of less than 2 cm and of more than 8 cm. Complicated monochorionic twin pregnancy, suspected to develop either selective fetal growth restriction or twin–twin transfusion syndrome (TTTS) is correct, as both severe types of pathology or even a combination of the two can develop from this situation. No estimated fetal weight is given, and no umbilical artery Doppler measurements are described. The deepest pocket of more than 6 cm before 16 weeks is considered by some centres to be sufficient to call this TTTS, although there is no consensus on this. It is likely that the smaller twin has a more marginally located cord insertion than the other twin, but this is not a diagnosis. The discrepancies are too large for physiological variation.

• 9.
  

  a) F b) F c) T d) F e) F

In singletons, this way of measuring the umbilical artery pulsality index is commonly performed and, in dichorionic twins, this is a way to make sure that the correct fetus is assessed. The typical Doppler patterns in monochorionic twins are caused by the vascular anastomoses, and the strongest effects are to be expected close to the placental surface. The angle should be as close to zero as possible as this increases the reliability of diagnosing absent end diastolic flow. An angle of more than 30° may falsely suggest the presence of absent end diastolic flow. A sample volume that is too large will distort the waveforms. The sample volume should just enclose the lumen of the artery.

• 10.
  

  a) F b) F c) F d) F e) T

Although signs of cardiac overload seem to be associated with a worse prognosis, expectant management leads to demise in 30–85% of cases. Even without signs of decompensation, sudden demise often occurs. The size and the growth rate may have some predictive value towards prognosis, but intervention in all cases seems to have the highest chance of survival. There is general consensus that signs of heart failure, such as a low a-wave in the ductus venosus, are a good reason to offer intervention. Robust signs of cardiac compromise such as cardiomegaly and DV waveform abnormalities are sufficient to guide clinical management in TRAP. Fetal echo may be interesting for research purposes only. Given the poor performance of predictive parameters, and the fact that sudden acute death is not uncommon, early intervention in all TRAP cases seems to be the preferred management.

• 11.
  

  a) F b) T c) T d) T e) F

Maternal pregnancy-related complications in multiple pregnancies are increased. The incidence of pregnancy-induced hypertension and anaemia are doubled. An increased incidence of labour dystocia, uterine atony, operative deliveries, postpartum haemorrhage and postnatal depression also occurs. A fivefold increase in neonatal mortality occurs after twin births compared with singletons and the risk becomes more in higher-order births. Prematurity is the main cause of neonatal morbidity, and is seen in almost one-half of all multiple pregnancies. Seventy-eight per cent of triplets and 48% of twins require neonatal admission compared with 15% of singletons. Mean gestational age for twins, triplets and quadruplets is 35, 33 and 29 weeks, respectively.

• 12.
  

  a) T b) T c) T d) F e) T

Overwhelming observational data indicate a significant reduction in the multiple pregnancy rate after DET compared with triple embryo transfer, with similar pregnancy rates in both groups. Elective single-embryo transfer is the most effective way of reducing multiple pregnancies. Because of concerns about a lower rate of pregnancies after fresh single-embryo transfer, the acceptability has been lower in worldwide practice. Evidence suggests that pregnancy rates after fresh single-embryo transfer compared with DET are lower. Multiple pregnancy rates are significantly reduced after single-embryo transfer. Recent evidence, however, suggests similar cumulative pregnancy rates after fresh single-embryo transfer and frozen cycles compared with DET. For optimising single-embryo transfer outcomes, an effective cryopreservation programme is essential. Evidence suggests that cumulative pregnancy rates after fresh single-embryo transfer with subsequent frozen cycles are similar to DET, with the advantage of lower multiple pregnancy rates.

• 13.
  

  a) F b) F c) T d) F e) T

TTTS does not present clinically in the first trimester. This may be because fetal urine only becomes the main component of amniotic fluid when fetal urine production becomes established from 16 weeks gestation, and the main feature of TTTS is polyhydramnios–oligohydramnios sequence secondary to increased urine production in the recipient and decreased urine production in the donor. Some have suggested that early pre-clinical signs of TTTS may present in the first-trimester scan, such as nuchal translucency discordance, crown–rump length discordance or abnormal ductus venosus waveforms. Studies of these parameters, however, have shown low sensitivity and variable specificity, and screening in the first trimester is not advised. Limited published evidence suggests fetal abnormality detection rates in twins, and triplet pregnancies are no different compared with singletons. Inter-twin membrane folding and liquor discordance have been shown to be good predictors of TTTS, but with poor specificity; therefore, it is recommended that frequency of scans is increased if they are present. No published evidence is available to guide how often and when screening scans for growth restriction in multiple pregnancy should be carried out. The NICE guideline found no studies supporting screening routinely with umbilical artery Doppler blood flow for fetal growth restriction.

• 14.
  

  a) F b) T c) F d) T e) F

No evidence has been published on the value of sexual abstinence in twin and triplet pregnancies. A systematic review of 21 studies concluded that transvaginal cervical length at 20–24 weeks’ gestation is a good predictor of spontaneous preterm birth in asymptomatic women with twin pregnancies. A National Institute of Health and Clinical Excellence guideline reviewed all published literature on cervical length and prediction of preterm labour, and found that the best cut-off at 20–24 weeks in twin pregnancy was 25 mm. A Cochrane systematic review of seven RCTs evaluating hospitalisation and bed rest in twin and triplet pregnancies to reduce preterm delivery found no evidence to support this intervention. A systematic review and meta-analysis of individual patient data of five RCTs of vaginal progesterone to prevent preterm delivery in pregnancy with a short cervix found that it reduced preterm delivery in singletons, but no such effect in twins. Cervical cerclage has not been found to be effective in twin or triplet pregnancies.

• 15.
  

  a) T b) F c) F d) F e) T

Maternal mortality in multiple pregnancy has been shown to be more than double than that of singleton pregnancies. Women with multiple pregnancies are at higher risk of haemorrhage antenatally and postpartum, but no published evidence supports routine supplementation of iron, folic acid, or both. Gestational diabetes results from relative insulin insufficiency secondary to the diabetogenic effect of placental hormones (e.g. human placental lactogen, progesterone and cortisol). The larger placental mass of multiple pregnancy increases the amount of these placental hormones, and therefore theoretically the risk of developing gestational diabetes. A RCT of specialist care (by midwives) in the UK showed no reduction in postnatal mental health problems. Other limited studies of various packages of specialist care have not evaluated the effect on postnatal mental health. Hypertensive disorders can present earlier and be more severe in twin pregnancy given the fact that there are two or more placental masses and they are placental diseases.

• 16.
  

  a) F b) F c) T d) F e) F

Most monochorionic twins will have an uneventful pregnancy, TTTS affecting only 12% of the monochorionic diamniotic pregnancies. TTTS is rare in monoamniotic twins. An imbalance of amniotic fluid amounts is the clinical manifestation of twin–twin transfusion and not its cause. The cause of TTTS is a shift of blood volume through placental vascular anastomoses, almost universally present in monochorionic placentas. Fetoscopic laser coagulation offers the best survival rates and neurological outcomes, and is thus considered the treatment of choice for severe TTTS. After 20 weeks’ gestation, the cut-off value for polyhydramnios in severe TTTS is 10 cm DVP. Otherwise, gestational age-related ranges of amniotic fluid in monochorionic twin pregnancies are not considered as cut-offs, as many stable moderate or stage I TTTS would be unnecessarily treated. Although anaemia in the donor twin and polycythaemia in the recipient twin is present in twin anaemia-polycythaemia sequence, which may be considered as a special form of twin-to-twin transfusion, the concept of TTTS involves a shift of blood volume through placental anastomoses without haemoglobin differences.

• 17.
  

  a) F b) T c) F d) T e) T

After week 20, the cut-off for severe polyhydramnios related to severe TTTS is 10 cm. This represents a typical case with moderate TTTS not yet fulfilling the criteria for fetoscopic laser therapy. At weekly follow ups, this pregnancy may remain stable or even regress to more balanced amniotic fluid amounts. If worsening occurs by entering stage I or higher stages, laser therapy may be offered. In the second case, the recipient twin has an advanced heart failure and it cannot be expected that the polyhydramnios will increase further and above 10 cm. Although the criteria for laser therapy are not strictly fulfilled, the procedure represents probably the last chance for this twin pair. Not all cases will progress from stage I to higher stages. Although this matter is currently still under investigation, and cases should indeed be followed up weekly, the natural course of TTTS can remain stable at stage I until a more advanced gestational age. An arrested or reversed end-diastolic flow in the umbilical artery of the donor twin implies an increased risk for intrauterine death after laser therapy. Fetoscopic laser coagulation can no longer protect the surviving twin, as volume shifts may already have lead to hypotensive hypoxic encephalopathy during the event of intrauterine death of its co-twin.

• 18.
  

  a) T b) F c) T d) F e) T

The insertion line of the inter-twin membrane is an important landmark, and vessels crossing this line are suspicious for ones running to the vascular equator. Sometimes anastomoses are located in the donor’s amniotic cavity, and laser coagulation has to be carried out through the membrane. All anastomoses have to be coagulated, irrespective of their flow direction or diameter. Especially, thin arterio-venous anastomoses that have been missed during the initial procedure may cause twin anaemia polycythaemia sequence during the remaining course of the pregnancy. On ultrasound examination immediately before the procedure, it is important to identify the placental area where the vascular equator may be expected. It is important to localise cord insertions and the site of the stuck twin. After selective coagulation of the anastomoses at the vascular equator, all coagulation sites are connected by a continuous coagulation line, which reduces the risk for extremely thin patent anastomoses, which may otherwise be missed (Solomon technique). Almost universally, arteries cross over veins and their colour can be distinguished during fetoscopy.

• 19.
  

  a) F b) T c) T d) F e) F

As in singleton pregnancies, cervical length shows a continuous reduction between 10 and 40 weeks. In contrast to singleton pregnancies, where the risk for preterm birth increases exponentially when the cervix is less than 15 mm, the cut-off for high risk in twin pregnancies is 25 mm, apparently because a longer cervix is needed to counteract the increased uterine activity during pregnancy. A recent meta-analysis showed that a cervical length of 25 mm or shorter was associated with 26% risk for birth before 28 weeks; in contrast, a longer cervix was associated with only 1.4% risk for birth before 28 weeks and about 65% chance for term birth. Cervical length, however, is a continuous variable and setting fixed cut-offs unavoidably introduces some degree of oversimplification. This happens because the risk increases exponentially after a certain point of shortening and because fixed cut-offs are clinically intuitive. Fetal fibronectin can be used in twin as in singleton pregnancies; however, a recent meta-analysis has shown that it has limited accuracy in the prediction of preterm birth, especially for outcomes other than birth before 32 weeks. A shifting trend has taken place towards screening in pregnancy as early as possible, preferably in the first trimester. In the case of cervical length, data on singletons are conflicting, and no studies have yet been conducted in twins.

• 20.
  

  a) F b) F c) F d) F e) T

As in singleton pregnancies, most women presenting with symptoms of preterm labour will not eventually deliver preterm. In fact, about 80% of cases in twins will not deliver within the next week and 60–70% will not deliver before 34 weeks. Published data on the prediction of preterm birth in twin pregnancies with symptoms of preterm labour are limited, and they are characterised by considerable heterogeneity. Two meta-analyses on the predictive performance of cervical length and fetal fibronectin have shown that both tests have limited accuracy, as they do not significantly change pre-test probabilities for preterm birth. Therefore, evidence-based recommendations for the use of these tests in this setting cannot be made presently. Available data are limited, especially for the most clinically relevant outcomes of birth within 48 h and 7 days from presentation, and it seems that the measurement of cervical length has only a minimal accuracy in predicting birth before 34 weeks. Although data show significant heterogeneity, cervical length measurement is a valid test in asymptomatic women and the area under the curve is around 80% for most cut-offs and outcomes. On the other hand, in symptomatic women cervical length has only a minimal accuracy in predicting birth before 34 weeks, as the positive and negative likelihood ratios are only 1.2 and 0.67, respectively. The main strength of fetal fibronectin is its high negative predictive value. In the case of twins, and keeping in mind that positive- and negative-predictive values are affected by the prevalence of the condition in question, a negative fetal fibronectin is associated with less than 2% risk of birth within 1 week.

• 21.
  

  a) F b) F c) F d) F e) F

Progesterone treatment in unselected twin pregnancies does not reduce the rate of preterm delivery before 34 weeks. In women with singleton pregnancies and a short cervical length at 20–23 weeks’ gestation, treatment with vaginal progesterone was been found to reduce the risk of delivery before 33 weeks of gestation by about 45%. In women with singleton pregnancies and a history of previous preterm delivery, progesterone treatment also significantly reduced the rate of perinatal complications. Results from singleton pregnancies, however, cannot be directly transferred to multiple pregnancies. More than 10 randomised-controlled trials of progesterone treatment in twin pregnancies have now been published, and none of these trials have found any effect of progesterone. In fact, the odds ratio of delivery before 34 weeks in twin pregnancies was 1.0 (95% CI 0.9 to 1.2). High-risk twin pregnancies (i.e. with a history of prior preterm delivery or short cervical length) have been less extensively studied, but again progesterone treatment does not seem to increase gestational length. Progesterone does not reduce perinatal mortality or perinatal morbidity in unselected twin cohorts. In high-risk twin pregnancies (i.e. women with a short cervix before 24 weeks’ gestation), there may be an effect on perinatal morbidity, but insufficient data are available to recommend this treatment outside randomised-controlled trials.

• 22.
  

  a) T b) T c) T d) F e) F

Progesterone may be administered intramuscularly as 17-α-hydroxyprogesterone caproate (17-OHPC), orally as natural progesterone, or vaginally as natural progesterone (gel or pessary). Intramuscular progesterone is administered once a week, and the dosage is 200–250 mg. Increase in dosage to 500 mg a week has not altered the effect of progesterone. Vaginal progesterone is given daily, in a dose of 90–400 mg a day. Oral progesterone treatment does have a large first-pass hepatic metabolism. At present longer-term harmful effects of progesterone treatment in infants born to mothers treated with progesterone is not indicated. Up to 2013, however, longer-term studies have only examined infants up to the age of 4 years for 17-OHPC and until 18 months for vaginal progesterone. Further longer-term follow-up studies are needed. Studies suggest that progesterone treatment increases the risk of intrahepatic cholestasis. One study found an increased risk of gestational diabetes in women treated with progesterone during the second- and third-trimester of pregnancy, but subsequent studies, including a meta-analysis, have not replicated this finding.

• 23.
  

  a) T b) T c) F d) F e) F

In a meta-analysis that included relatively sparse data from twin pregnancies, the rate of preterm birth before 35 weeks was 75.0% in the cerclage group compared with 36.0% in the control group. The total number of pregnancies included in the meta-analysis was 49, resulting in a wide confidence interval for the relative risk of preterm birth (relative risk 2.2; 95% CI 1.2 to 4.0). Similarly, perinatal mortality was higher in women with twin pregnancies who had a cervical cerclage compared with a control group without any surgical intervention (22.9% v 6.0%). This resulted in a relative risk of 2.7 (95% CI 0.8 to 8.5). Data on women with twin pregnancies and a short cervical length are sparse, but a small retrospective study suggested that emergency cerclage may reduce the rate of preterm delivery in women with a short cervix. The cervical cerclage technique is no more difficult to perform in twins.

• 24.
  

  a) F b) T c) F d) T e) F

A cervical pessary closes the cervical canal tightly, thus protecting the mucus plug, providing support to the cervix, and also changing the angle of the cervical canal to become more acute. If the cervical canal angle does not change with insertion of a pessary, as estimated by magnetic resonance imaging, this may be associated with preterm delivery. In a large randomised-controlled trial in singleton pregnancies, insertion of the Arabin pessary reduced the rate of preterm delivery from 27% to 6%. The effect has been investigated in several other randomised-controlled trials in singleton and twin gestations, but results are not yet available. The preliminary data from a Dutch, multicentre, randomised-controlled trial, however, showed no reduction in preterm delivery rate before 32 weeks (9% v 12%) nor before 37 weeks of gestation (54% v 57%). The cervical pessary may have a place in the treatment of women with a short cervical length, but this remains to be investigated in properly designed randomised-controlled trials. In the one randomised-controlled trial of twin pregnancies thus reported, no difference was found in the rate of adverse perinatal outcome between women treated with a cervical pessary and controls. In fact, 42 women (11%) in the pessary group and 42 women (11%) in the control group delivered at least one child with an adverse neonatal outcome. Again, in women with short cervical length at 16–20 weeks, there may be an effect as the rate of adverse neonatal outcome was 10% in the group treated with a pessary compared with 25% in the group without treatment. There do not appear to be any significant adverse maternal effects associated with cervical pessary use.

• 25.
  

  a) F b) T c) T d) F e) F

‘Term’ should still be calculated at 40 weeks after the last menstrual period even though delivery is recommended at an earlier gestation. Stillbirth rates are much higher for twin pregnancies compared to singletons after 38 weeks. Optimal time of delivery is controversial, as a balance needs to be made between still birth rate, which is increased, and respiratory distress syndrome, but most would advocate delivery at 38 weeks. Sixty per cent of first twins present in a cephalic position.

• 26.
  

  a) T b) F c) F d) F e) F

This is correct, and is the main finding of the Twin Birth Study which showed no difference in the primary outcome of twins in whom vaginal birth was planned compared with those in whom lower segment caesarean section was planned. In the Twin Birth Study no difference was found in maternal outcome between the groups. The risk of caesarean birth for the second twin in the Twin Birth Study was 4%, and in most studies it is less than 10%. In the Twin Birth Study no association was found of the primary outcome with either parity or chorionicity.

• 27.
  

  a) F b) F c) F d) F e) T

In the Twin Birth Study the position of the second twin was not related to primary outcome. External cephalic version is less than successful at achieving vaginal birth of the second twin than breech extraction with or without intravenous therapy. This has been found to be true in all comparative studies and in the Twin Birth Study. In about 20% of cases, the second twin will change position after the first is delivered. In the Twin Birth Study the mean Twin–Twin delivery interval was 5 minutes. Data from the Twin Birth Study showed that adverse outcome for the second twin is not prevented by Caesarean Section.

• 28.
  

  a) F b) F c) T d) F e) T

Delivery room delivery is advised against as the position of the second twin changes frequently and rapidly (20%). Although lower segment caesarean section is uncommon, it may be urgent and time may be saved if delivery takes place in the operating theatre with all staff available. Continuous monitoring is required to ensure that each twin is being monitored separately. Urgent breech extraction or vacuum, which is not uncommon, requires analgesia. The rate is less than 10% in most studies. Contractions often diminish after delivery of the first twin and need augmentation.

• 29.
  

  a) T b) T c) T d) F e) T

Outcome of twin pregnancy is largely determined by whether they share a single placenta or not. Zygocity is much less important unless parents are carriers of a genetic syndrome. Twin to twin transfusion syndrome (TTTS) and selective fetal growth restriction are known complications of MCDA twins and they are due to vascular anastomoses in the placenta and unequal placental sharing respectively. MCDA twins could be borne with large inter-twin haemoglobin difference without features of TTTS and this entity is described as twin anemia-polycythemia sequence (TAPS). TAPS usually presents in late pregnancy during labour or post Laser therapy for TTTS. Birthweight discordance >25% is an independent predictor of pregnancy outcome in both MCDA and DCDA twins.

• 30.
  

  a) F b) T c) T d) F e) T

Perinatal mortality and morbidity of twins almost equal that of 41 weeks singleton pregnancy. Therefore, delivery should be considered for uncomplicated DCDA after 38 weeks. MCDA twins carry higher risk of still births than DCDA, this difference is statistically significant throughout pregnancy and therefore, frequent antenatal fetal monitoring is justifiable in MCDA twins. However, risk of stillbirth in MCDA at 34 and 37 week is not different. Therefore, preterm delivery at 34 weeks for MCDA is not justified.