HKCOG Guidelines November 2006 Guidelines On
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Number 11 Part II HKCOG Guidelines November 2006 Guidelines On Management of Multiple Pregnancies: Part II published by The Hong Kong College of Obstetricians and Gynaecologists A Foundation College of Hong Kong Academy of Medicine 1 AIM rather than the percentage of the discordance. Part II of the guideline aims to examine the specific antenatal complications related to ii. Single intrauterine fetal demise (IUFD) particular types of twin pregnancies, the timing and the mode of delivery, the intrapartum The cause of intrauterine death and the management of vaginal deliveries of twins, and gestational age are the two main the controversy of delayed interval delivery of determining factors in the clinical decision the second twin in very preterm gestation. of delivery or expectant management. 2 SPECIFIC ANTENATAL The decision to deliver the pregnancy or to COMPLICATIONS RELATED adopt expectant management in case of TO THE TYPE TO TWINS single IUFD in DC pregnancies depends on the cause of the intrauterine fetal death and a. Dichorionic (DC) twins: the gestational age. As the placentas are separate, there is no worry of damage to the i. Discordant fetal growth surviving twin due to hypotensive or embolic phenomena, as in the case of monochorionic (MC) pregnancies. If the The indication for delivery should take into cause of the intrauterine fetal death is consideration of the fetal well-being(s), the unlikely to result in problem of the gestational age and serial growth velocity surviving twin or the gestational age is in case of discordant fetal growth. remote from term, expectant management is appropriate and the neonatal outcome is In multiple pregnancies, discordance in fetal usually good 3. Although maternal growth is calculated by dividing the disseminated intravascular coagulopathy difference in the estimated weights of the 1 after IUFD is a potential risk, it is extremely fetuses by the weight of the larger fetus . In rare 4. DC pregnancies, some form of difference in the fetal size can be normal as both fetuses b. Monochorionic diamniotic (MCDA) twins: may have different genetic make-up, especially if both still have normal parameters for the gestational age. It has i. Twin-twin transfusion syndrome been shown that the risk of fetal death begins to increase progressively when the Monochorionic pregnancies should weight discordance exceeds 25% 2. Hence, be monitored closely with ultrasonography it appears logical to offer close fetal for development of TTTS. surveillance if the discordance exceeds 20- 25% 1. Discordant fetal growth can be due Twin-twin transfusion syndrome (TTTS) is to different genetic growth potentials, a severe condition that complicates up to 5 structural anomaly of one fetus, or an 15% of all MCDA pregnancies . It is unfavourable placental implantation. The believed to occur as the result of indication for delivery should take into uncompensated arteriovenous anastomoses consideration of the fetal well-being(s), the in the placenta, leading to a net flow of 6 gestational age and serial growth velocity blood from one twin to the other . The HKCOG GUIDELINES NUMBER 11 – Part II (November 2006) donor twin is usually anaemic, growth mainly due to acute hypotensive episode at restricted and oliguric with oligohydramnios; the time of the fetal demise 15. The risks of whereas the recipient twin is usually perinatal mortality and serious neurological plethoric, polyuric with polyhydramnios and impairment among survivors have been may develop congestive heart failure and reported in 30% and 10-20% of cases fetal hydrops. It can occur at any time respectively 3, 16. If single IUFD occurs after during pregnancy but severe cases which successful fetoscopic laser therapy for present before 26 weeks are associated with TTTS, the risk of damage to the surviving high risks of perinatal mortality and twin is lower 17. The best management of handicap among the survivors 7-9. Untreated, single IUFD in MC pregnancies remains the perinatal mortality is up to 90% 5. unknown. Immediate delivery of the surviving twin in this circumstance may not Prenatal diagnosis of TTTS is based on prevent the occurrence of neurological sonographic features of inter-twin blood complications 15. Gestational age appears to flow discordance, including polyhydramnios be a logical guide to the decision on (≥8cm vertical pocket) and a full bladder delivery. If it is remote from term, expectant due to polyuria in the recipient, and severe management with close maternal and fetal oligo- or anhydramnios (≤1 or 2cm vertical surveillance is advised. If neonatal survival pocket) in the donor with small or absent is likely, immediate delivery might be a bladder filling 10, 11. Discordant fetal growth better option to avoid any possible late co- is commonly seen in TTTS but is not an twin sequelae, although some early damage essential diagnostic feature. As it only might have already occurred. Neonatal occurs in MC pregnancies, the diagnosis of cranial ultrasound is recommended after chorionicity in early pregnancy is important. delivery. Great discrepancy in the nuchal translucency thickness 8, inter-twin iii. Twin reversed arterial perfusion sequence membrane folding 12 and disparity in fetal size in MC pregnancy 13 might be early The choice of treatment for TRAP depends signs of TTTS in the first trimester. Even if on the size and growth of the acardiac twin the first trimester scan is normal, regular and the cardiovascular status of the pump ultrasonography at ~2 weeks’ interval twin. between 16 and 26 weeks is advised 10. If TTTS is suspected, patient should be Acardiac anomaly in one of the twins, referred to a specialized fetal medicine also known as twin reversed arterial centre for prompt assessment. perfusion sequence (TRAP), is a rare complication unique to MC pregnancies. The main treatment options for TTTS The reported incidence is 1 in 100 MC twins include fetoscopic laser coagulation of the and 1 in 30 monozygotic triplets 18, 19. The communicating placental vessels and serial primary malformation is the lack of a well- amniodrainage. Fetoscopic laser therapy is defined cardiac structure in one twin (the technically more demanding and should be acardiac twin), which is kept alive by its performed in specialized fetal medicine structurally normal co-twin (the pump twin) centres 14. It has been shown in a through a superficial artery-to-artery randomized trial to offer higher survival rate placental anastomosis 18. The perinatal and better neurological outcome among mortality of the pump twin is over 50%, survivors during the first 6 months of life mainly due to high output heart failure or for TTTS diagnosed before 26 weeks of preterm birth 19. The diagnosis is by gestation, compared with amniodrainage 11. ultrasound. Care must be taken in not Serial amniodrainage, on the other hand, is mistaking TRAP as single missed abortion technically simpler. It should be offered in in a multiple pregnancy and colour situations when laser therapy is technically Doppler should help in establishing the difficult or not available, or when TTTS is correct diagnosis. Treatment modalities diagnosed after 26 weeks 5. include conservative treatment with ultrasound surveillance, medical treatment ii. Single intrauterine fetal demise for heart failure of pump twin, interruption of the vascular connection by intrafetal Single IUFD in MC pregnancies carries ablation and cord occlusion. The choice significant risks to the surviving co-twin. depends on the prognostic indicators, including the size and growth of the In MC pregnancies, single IUFD poses a acardiac twin and the cardiovascular status significant risk to the surviving co-twin, of the pump twin 20. 2 HKCOG GUIDELINES NUMBER 11 – Part II (November 2006) c. Monochorionic monoamniotic (MCMA) Because of the high perinatal mortality, twins: prophylactic delivery by caesarean section at 32 to 34 weeks is recommended 27, 28. Monoamniotic twining occurs in only 1% of monozygotic twins but is associated with 10-20 % of perinatal mortality 21, 22. In 3 TIMING OF DELIVERY FOR addition to problems related to MC UNCOMPLICATED MULTIPLE pregnancies, this type of twining is also PREGNANCIES associated with specific complications, including conjoined twins and cord accident Delivery should be considered at 38 and 34-36 secondary to cord entanglement. weeks of gestation for twins and triplets respectively if still not delivered by then. i. Conjoined twins The perinatal mortality for twin pregnancies Accurate prenatal diagnosis of conjoined starts to rise at 37-38 completed weeks of gestation, compared with 40-41 weeks twins by ultrasonography is possible in the 29, 30 first trimester. in singletons . By 39 weeks, the prospective risk of fetal death in twins also outweighs the 30 Conjoined twins are a rare complication of risk of neonatal death . Therefore, for monoamniotic twining, with an incidence of uncomplicated twin pregnancies, delivery should around 1: 55,000 pregnancies 23. Accurate be considered at 38 completed weeks of prenatal diagnosis is possible in the first gestation if there is no onset of labour. Similarly, the prospective risk of fetal death in triplets trimester and allows better counseling of the 30 parents regarding the management options. exceeds the risk of neonatal death at 36 weeks . Sonographic findings include features of It is generally considered appropriate to deliver monoamnionicity, inseparable fetal bodies triplets between 34- 36 weeks since the fetal and skin contours, and an unchanged lung is rather mature and the huge gravid uterus relative position of the fetuses 24. It is also usually causes significant maternal discomforts important to note that both false-positive by this gestation. and false-negative cases of conjoined twins have been reported when the diagnosis is 25 4 MODE OF DELIVERY made before 10 weeks of gestation . Repeated ultrasound examination for a. Twins confirmation of the diagnosis between 11- 14 weeks is advised. The condition carried 25 Vaginal delivery is an appropriate mode of very poor prognosis .