With the development of assisted reproductive technology and the increase in the number of elderly pregnant women, the incidence of twin pregnancies is increasing year by year. Twin pregnancy has become an important cause of miscarriage, preterm birth, birth defects and increased perinatal morbidity and mortality. However, there is no definite epidemiological data on twin pregnancies in China, and there is a lack of evidence-based guidelines for the diagnosis and management of twin pregnancies in China. For this reason, the Fetal Medicine Group of the Perinatal Medicine Branch of the Chinese Medical Association and the Obstetrics and Gynecology Group of the Obstetrics and Gynecology Branch of the Chinese Medical Association have organized national experts to discuss and prepare this guideline. The guidelines are mainly based on a review of important foreign literature on twin pregnancy, combined with the current situation of clinical practice in China, and with reference to the 2011 Royal College of Obstetricians and Gynaecologists (RCOG), 2011 French Society of Obstetrics and Gynaecology, 2014 American College of Obstetricians and Gynaecologists, and 2006 Hong Kong Society of Obstetricians and Gynaecologists. This guideline summarizes some of the currently accepted or near-accepted opinions in the academic community and provides a recommendation level for reference.
The grades of evidence-based medicine indicated in this guideline: Grade Ia evidence: from randomized controlled meta-analysis literature; Grade Ib evidence: from at least 1 randomized controlled study; Grade IIa evidence: from at least 1 rigorously designed non-randomized controlled study; Grade IIb evidence: from at least 1 rigorously designed experimental study; Grade III evidence: from at least 1 well-designed, non-experimental descriptive study, such as Correlational analysis studies, comparative analysis studies, or case reports; Level IV evidence: from expert committee reports or the experience of authoritative experts.
The classification of recommendation levels marked in this guideline: Level A: supported by good and coherent scientific evidence (supported by randomized controlled studies, such as Level I evidence); Level B: supported by limited or incoherent literature (lack of randomized studies, such as Level II or III evidence); Level C: based mainly on expert consensus (such as Level IV evidence); Level E: empirical findings, empirical recommendations for clinical practice, lacking scientific literature support .
This guideline is divided into 3 parts: the first part focuses on the standardization of antenatal examination during pregnancy, gestational monitoring, prevention of preterm delivery and choice of delivery method for twin pregnancies; the second part focuses on the management of special problems of twin pregnancies; the third part focuses on a series of expert consensus on the diagnosis and treatment of complex multiple pregnancies that are still controversial.
It is hoped that this guideline will serve as a guide for future multicenter epidemiological studies of twin pregnancies in China, standardize the diagnosis, treatment and referral process of twin and even multiple pregnancies, and standardize the intrauterine treatment of complicated multiple pregnancies. This guideline is not a mandatory standard, nor can it include and address all issues in twin pregnancies. This guideline will be refined and updated as new evidence-based medical evidence becomes available.
I. Determination of twin fetal chorionicity
Question 1: How to determine the chorionicity of twin pregnancies?
(1) If a twin pregnancy is detected by ultrasonography in early or mid pregnancy (6-14 weeks of gestation), the determination of chorionicity should be performed and the relevant ultrasound images should be preserved (recommended grade B).
(2) If there is difficulty in determining chorionicity, prompt referral to a regional prenatal diagnosis center or fetal medicine center is required (recommended grade E). The majority of dizygotic twins are dichorionic bimniotic twins, whereas monochorionic twins evolve into bimniotic bimniotic twins or monochorionic bimniotic twins, depending on the time of division; if division occurs later, monochorionic monoamniotic twins or even conjoined twins are formed. Therefore, monochorionic twins are monozygotic twins, whereas dichorionic twins are not necessarily dizygotic twins. The risk of brain damage to the surviving fetus if one of the fetuses dies in utero is due to the characteristics of the anastomosing branch of the placenta. The risk of brain damage to the surviving fetus if one of them dies in utero. Therefore, the diagnosis of chorionicity is essential for the evaluation and management of twin fetuses during pregnancy. The risk of intrauterine fetal death in monochorionic twin pregnancies is 3.6 times higher than in dichorionic twins, and the risk of miscarriage before 24 weeks of gestation is 9.18 times higher (level of evidence IIa).
At 6 to 9 weeks of gestation, chorionicity can be determined by the number of gestational sacs. From 10 to 14 weeks of gestation, chorionicity can be determined by the morphology of the amniotic-placental junction between the twin fetuses. The amniotic membrane of single chorionic twin fetuses is separated from the placenta in a “T” sign, while the fusion of the fetal membranes of double chorionic twins is interspersed with placental tissue, so the fusion of the placenta shows a “double fetal peak” (or “λ” sign). (or “λ” sign). The “twin fetal peaks” or “T” sign is not easy to determine in the middle of pregnancy, and the chorionicity can only be determined by the number of separated placentas or the sex of the fetus. If there are two placentas or different sexes, then it is a double chorionic twin; if two fetuses share one placenta with the same sex, and there is a lack of ultrasound data in early pregnancy, chorionicity can be very difficult to determine. In the past, chorionicity was determined by the thickness of the amniotic membrane separation, but the accuracy was not good. If the diagnosis of chorionicity is unclear, it is recommended to treat the pregnancy as a single chorionic twin (evidence level IIa or IIb).
II. Prenatal screening and prenatal diagnosis of twin pregnancies
Question 2: How to perform prenatal aneuploidy screening and screening for twin structures in twin pregnancies?
(1) Ultrasound screening at 11-13 weeks of gestation +6 can assess the risk of Down syndrome in the fetus by detecting nuchal translucency (NT) and can detect some severe fetal anomalies early (recommended grade B).
(2) Screening for Down’s syndrome in twin pregnancies using midtrimester biochemical serology alone is not recommended (recommended grade E).
(3) Ultrasound screening for twin fetal structures is recommended at 18 to 24 weeks of gestation. The quality of structural screening is easily affected by the fetal position of the twin fetuses, and structural screening including the fetal heart can be performed in stages according to the gestational weeks in hospitals where available (recommended grade C).
For twin chorionic twin pregnancies, 11-13 weeks of gestation +6 twin NT tests combined with fetal nasal bone, venous catheter, and tricuspid regurgitation have a detection rate of up to 80% for Down syndrome, which is similar to the screening results for singleton pregnancies. For single chorionic twins, the risk of Down syndrome should be calculated for 1 fetus (using the average of the maximum head-rump length and NT). For dichorionic twins, the risk of Down’s syndrome should be calculated independently for each fetus, since most are dizygotic twins (level of evidence IIa or IIb).
In the literature, the detection rate of Down syndrome in mid-pregnancy serologic screening for singleton and twin pregnancies is 60-70% and 45%, respectively, with a false-positive rate of 5% and 10%, respectively. Because of the low detection rate and high false-positive rate of twin gestation screening, the use of serologic indicators alone for aneuploidy screening in twin pregnancies is not currently recommended. The probability of fetal structural abnormalities in twin pregnancies is 1.2 to 2.0 times higher than in singleton pregnancies. In dizygotic twin pregnancies, the probability of fetal anomalies is similar to that of monozygotic pregnancies; whereas in monozygotic twins, the incidence of fetal anomalies increases 2 to 3 times. The most common malformations are cardiac malformations, neural tube defects, facial developmental abnormalities, gastrointestinal developmental abnormalities, and abdominal wall clefts. Early prenatal diagnosis of some severe fetal structural anomalies, such as anencephaly, cervical hydrocele and severe cardiac anomalies, can be made when fetal NT testing is performed early in pregnancy (level of evidence IIb).
Ultrasound structural screening for twin pregnancies is recommended at 18 to 24 weeks of gestation and no later than 26 weeks. Twin pregnancies are more difficult to screen because the quality of structural screening is easily affected by the fetal position. Medical institutions that have the means to do so can perform structural screening including fetal heart in separate sessions according to the gestational weeks and refer to regional prenatal diagnostic centers (evidence level III or IIb) promptly if suspicious abnormalities are found.
Question 3: How to perform cytogenetic diagnosis of twin fetuses?
【Expert opinion or recommendation】 (1) For pregnant women with indications for cytogenetic screening, prompt prenatal diagnostic counseling should be given (recommendation level E).
(2) The rate of fetal loss associated with invasive prenatal diagnostic operations is higher in twin pregnancies than in singleton pregnancies. Referral to a prenatal diagnostic center capable of performing intrauterine intervention is recommended (recommended grade B).
(3) For dual chorionic twins, both fetuses should be sampled. In monochorionic twins, usually only one of the fetuses should be sampled; however, in the presence of structural abnormalities in one fetus or severe disparity in size and development in both fetuses, both fetuses should be sampled separately (recommended grade B).
The indications for chromosomal testing in twin fetuses are similar to those for singleton pregnancies. It is important to note that the probability of Down syndrome in monozygotic twins is similar to that in monozygotic twins, whereas the probability of chromosomal abnormality in 1 of the dizygotic twins is 2 times higher than that of monozygotic pregnancies in the same age group. It has been suggested that the risk of Down’s syndrome in dizygotic twin pregnancies at age 32 years is similar to that in singleton pregnancies at age 35 years. Prenatal diagnostic counseling for twin pregnancies needs to be individualized and a decision made by both partners. Chorionic villus sampling or amniocentesis may be performed in twin pregnancies. One study showed that amniocentesis resulted in a 1.6% rate of twin fetal loss by 24 weeks of gestation and chorionic villus puncture resulted in a 3.1% rate of twin fetal loss by 22 weeks of gestation. Because of the subsequent management involved after detection of 1 fetal abnormality (e.g., selective reduction), cytogenetic testing of twin fetuses should be performed at a diagnostic prenatal center with the capacity to perform intrauterine fetal interventions. Prior to amniocentesis or chorionic villus sampling, each fetus should be marked (e.g., placental position, fetal sex, point of umbilical cord insertion, fetal size, presence of anomalous features, etc.). Identification of the amniotic cavity in which a particular fetus is located by intra-amniotic injection of indocyanine is not recommended. Sampling of 2 amniotic cavities is recommended for early chorionic villous indistinctness, or for monochorionic twin fetuses in which 1 fetus has structural abnormalities and the 2 fetuses have large differences in body mass (level of evidence IIb).
III. Monitoring of twin fetuses during pregnancy
Question 4: How to perform gestational monitoring of twin chorionic villus twins?
Expert opinion or recommendation】 Dual chorionic villus twins require more antenatal visits and ultrasound monitoring than singleton fetuses and require experienced physicians to manage this high-risk pregnancy during pregnancy (level of recommendation B).
Twin pregnancies should be managed as high-risk pregnancies. At least 1 prenatal visit per month in the middle of pregnancy is recommended. Since twin pregnancies have a higher rate of gestational complications than singleton pregnancies, it is recommended that the number of antenatal visits be increased appropriately in the late stages of pregnancy. Ultrasound assessment of fetal growth and development and cord blood flow Doppler testing should be performed at least once a month. It is recommended to increase the number of ultrasound assessments of the fetus in late pregnancy as appropriate to facilitate further detection of possible differences in twin fetal growth and development and to accurately assess the intrauterine health status of the fetus. Iron deficiency anemia is more common in twin pregnancies with increased gestational requirements for calories, protein, trace elements and vitamins (Level of Evidence IIb).
Question 5: How to perform gestational monitoring of monochorionic twin pregnancies?
(1) Gestational monitoring of single chorionic villus and double amniotic sac twins requires close cooperation between obstetricians and ultrasonographers. If abnormalities are detected, early referral to a qualified prenatal diagnostic center or fetal medicine center is recommended (recommendation level B).
(2) On the basis of well-informed information, monitoring of monochorionic monoamniotic sac twin fetuses in late pregnancy should be intensified, and termination of pregnancy should be done when appropriate (recommended grade C).
Because of the high rate of perinatal disease and mortality, ultrasound examination is recommended at least every 2 weeks starting at 16 weeks of gestation. The examination is performed by an experienced sonographer and the evaluation includes the growth and development of the twin fetuses, amniotic fluid distribution and fetal umbilical artery flow and, if appropriate, fetal middle cerebral artery flow and venous ductal flow. Due to the unique nature of monochorionic twins, some serious complications of monochorionic twins such as TTTS, selective intrauterine growth restriction (sIUGR) and one of the twin malformations may produce a poor pregnancy outcome. A comprehensive assessment of maternal and fetal risk in an experienced fetal medicine center is recommended, taking into account the patient’s wishes, cultural background and economic conditions to develop an individualized treatment plan (Level of Evidence IIb).
Monochorionic monoamniotic sac twin fetuses may have intertwined umbilical cords in the early and middle stages of pregnancy, resulting in a high fetal mortality rate. Antenatal visits need to adequately inform the pregnant woman of the risk of unpredictable fetal death. Regular ultrasound examinations are recommended to assess fetal growth and Doppler flow and, at the appropriate gestational weeks, to detect early signs of fetal distress by electronic monitoring of the fetal heart. For this type of twin birth, delivery at a medical center with some competence in prematurity diagnosis and management is recommended. Cesarean section is the recommended mode of delivery. Termination of pregnancy at 32-34 weeks of gestation is recommended in order to minimize the risk to the fetus during the continuation of the pregnancy and to promote fetal lung maturation before termination of pregnancy.
IV. Diagnosis, prevention and treatment of preterm delivery in twin pregnancies
Question 6: What is the relationship between obstetric history and clinical symptoms and preterm labor?
[Expert opinion or recommendation] Previous history of preterm labor is closely associated with the occurrence of preterm labor in twin pregnancies (recommendation grade B).
Michaluk et al. conducted a retrospective analysis of 576 twin pregnancies with a history of singleton preterm delivery and found that preterm delivery (<37 weeks of gestation) occurred in 309 cases (53.6%). Multifactorial analysis showed that previous history of preterm delivery was an independent risk factor for preterm delivery in twins (OR=3.23, 95% CI: 1.75-5.98) and was not associated with the timing of previous preterm delivery (level of evidence IIa).
Question 7: Can cervical length measurement predict preterm birth?
Expert opinion or recommendation] Transvaginal cervical length measurement and transvaginal detection of fetal fibronectin can be used to predict the occurrence of preterm labor in twin pregnancies, but there is no evidence to suggest which method is more advantageous (level of recommendation B).
Most authors agree that a cervical length of <25 mm in twin gestation at 18-24 weeks of gestation is the most desirable predictor of preterm delivery. Some scholars also suggest that in asymptomatic twin pregnancies, routine assessment of the risk of preterm labor by transvaginal ultrasound monitoring of cervical length, detection of fetal fibronectin and monitoring of contractions is not recommended. Most domestic scholars advocate measuring cervical length at the same time as ultrasound structural screening at 18 to 24 weeks of gestation.
Question 8: Can bed rest reduce the incidence of preterm labor in twin pregnancies?
There is no evidence that bed rest and inpatient observation improve the outcome of twin pregnancies (recommendation level A).
Several meta-analyses have shown that bed rest and contraction monitoring do not reduce the rate of preterm delivery and neonatal intensive care unit (NICU) admission in twin pregnancies without high-risk factors. In contrast, for those with cervical dilatation >2 cm, inpatient monitoring reduced the preterm birth rate and increased neonatal birth mass, but did not significantly reduce the NICU admission rate. A study of 2,422 pregnant women at risk of preterm delivery (844 of whom had twin pregnancies) found no statistically significant difference in the rate of preterm delivery with daily and weekly nurse care, and an increase in the number of visits with daily nurse care and an increase in the use of preterm delivery medications (evidence level Ia or IIa).
Question 9: Can cervical cerclage prevent the occurrence of preterm birth in twin pregnancies?
There is no evidence that cervical cerclage prevents preterm delivery in twin pregnancies (level of recommendation B).
The risk of preterm delivery in pregnant women with short cervix in twin pregnancies monitored by ultrasound was twice as high as in those without shortened cervix even after completion of cervical cerclage.Miller et al. observed 176 pregnant women with twin pregnancies, of whom 76 had cervical cerclage and 100 were controls.Multifactorial regression analysis showed no significant association between cervical cerclage and gestational week of delivery, while a history of previous preterm delivery or multiple births Elective cervical cerclage in pregnant women may improve pregnancy outcomes (Level of evidence IIb).
Question 10: Can progesterone prevent the occurrence of preterm birth in twin pregnancies?
Expert opinion or recommendation] Progestin preparations, whether administered vaginally or intramuscularly, do not change the outcome of preterm birth (level of recommendation B).
Senat et al. conducted a randomized controlled study of asymptomatic twin pregnancies with a cervical length <25 mm at 24 to 31 weeks of gestation. The time from dosing to delivery was 51 (36-66) d in the study group and 45 (26-62) d in the control group after 2 weeks of intramuscular progestin treatment, with no statistically significant difference between the 2 groups. A multicenter study of 671 pregnant women with progressive shortening of the cervix in twin pregnancies found that the cervix shortened by 1.04 mm per week in those using progestin compared to 1.11 mm in the control group, with no statistically significant difference between the 2 groups; therefore, there was no significant association between cervix shortening and progestin application (level of evidence IIa or III).
Question 11: Is the method of promoting fetal lung maturation in twin pregnancies different from that in single pregnancies?
Expert opinion or recommendation] In twin pregnancies with a high risk of preterm delivery, glucocorticoid fetal lung maturation therapy can be administered in the same way as in singleton pregnancies (recommendation level C).
In the 2010 RCOG guidelines, it was stated that a single course of glucocorticoids applied to singleton pregnancies at high risk of preterm delivery before 34 weeks + 6 weeks of gestation reduces the incidence of respiratory disease, necrotizing small bowel colitis, and intraventricular hemorrhage in preterm infants, but there is no evidence to support this for twin pregnancies. The NIH recommends that in twin pregnancies with a high risk of preterm delivery within 1 week, glucocorticoid treatment for fetal lung maturation may be administered as for singleton pregnancies if not contraindicated. There is no evidence to support the need for repeat dosing for fetal lung maturation in twin pregnancies. A retrospective analysis of neonatal outcomes in 88 pregnancies with single-dose glucocorticoids and 42 pregnancies with twin preterm births treated with 2 doses of glucocorticoids found no difference in the incidence of neonatal respiratory distress syndrome (NRDS) between the 2 groups and therefore did not support repeat dosing in twin pregnancies ( Evidence level IV or III).
Question 12: Can contraction inhibitors prevent the occurrence of preterm delivery in twin pregnancies?
Similar to singleton pregnancies, the use of contraction inhibitors in twin pregnancies may extend the gestational cycle for a shorter period of time to allow for fetal lung maturation and intrauterine transit (level of recommendation B).
Similar to singleton pregnancies, the use of contraction inhibitors in twin pregnancies may extend the gestational cycle for a shorter period of time to allow for fetal lung maturation and intrauterine transit. Several meta-analyses have demonstrated the fetal neuroprotective effect of magnesium sulfate in pregnant women born prematurely at <32 weeks of gestation, in both single and twin pregnancies, reducing the incidence of neonatal cerebral palsy. There is no definite conclusion about the timing and specific application dose of magnesium sulfate, and individualized protocols need to be developed according to the patient's contractions, the purpose of treatment and maternal-fetal monitoring (Level of evidence Ia).
V. Mode of delivery and gestational week of delivery in twin pregnancies
Q13: How to choose the mode of delivery in twin pregnancies?
(1) The mode of delivery for twin pregnancies should be determined based on chorionicity, fetal orientation, maternal history, pregnancy complications and complications, cervical maturity and intrauterine fetal condition, etc., and an individualized plan should be formulated.
(2) In view of the differences in medical conditions between hospitals at different levels in China, physicians should fully communicate with patients and their families to make them understand the possible risks and management options during vaginal delivery of twin fetuses, the immediate and long-term risks of cesarean delivery, weigh the pros and cons, make individualized analysis, and decide on the delivery method together (recommendation level E).
In the 2013, Twin Birth Study Collaborative Group multicenter study, 1,398 pregnant women with 1 fetal head position and 32 to 38 weeks of gestation +6 twins were randomized into a planned cesarean delivery group and a planned vaginal delivery group. The elective cesarean group was planned for surgical delivery at 37 weeks +5 to 38 weeks +6. The cesarean delivery rate was 90.7% in the planned cesarean group compared with 43.8% in the planned vaginal delivery group, with no statistically significant difference in poor perinatal prognosis between the 2 groups (2.2% and 1.9%, respectively; P=0.49). Therefore, there is no evidence to support that planned cesarean delivery improves perinatal prognosis (level of evidence Ia).
Question 14: Does chorionic villus performance influence the choice of delivery method in twin pregnancies?
[Expert opinion or recommendation] Vaginal trial of labor is an option for single chorionic villus double amniotic sac twins and double chorionic villus double amniotic sac twins without comorbidities. For monochorionic mono-amniotic sac twins, cesarean section is recommended (recommendation grade B).
In a 2011 retrospective study of 465 uncomplicated monochorionic twins, the success rate of vaginal trial of labor was 77%, the incidence of stillbirth during the trial was 0.8%, and the perinatal mortality rate after 37 weeks of vaginal delivery was 0.7%. The perinatal mortality rate was 0.7%. The incidence of NRDS increases with elective cesarean delivery before 36 weeks of gestation. Monochorionic twins have an anastomotic branch of interplacental vascular traffic, and the rate of acute twin transfusion during labor is 10%. Intensive monitoring during labor is needed, especially for small fetuses, to be alert for fetal distress due to insufficient placental perfusion or umbilical cord factors. The incidence of cord entanglement in single chorionic villus single amniotic sac twins is high and sudden intrauterine death due to cord entanglement may occur throughout the pregnancy including the perinatal period, so cesarean section is recommended for termination of pregnancy (level of evidence IIa).
Question 15: How to decide the optimal gestational week for delivery of twin pregnancies?
(1) It is recommended that delivery should be considered at 38 weeks of gestation for twin chorionic twins without complications or comorbidities (level of recommendation B).
(2) Delivery of single chorionic villus twin fetuses without complications or comorbidities can be monitored closely until 37 weeks of gestation (recommendation grade B).
(3) The recommended gestational week of delivery for monochorionic monoamniotic sac twins is 32-34 weeks, or the gestational week of delivery can be delayed according to the condition of the mother and fetus (recommended grade C).
(4) Complex twin pregnancies (e.g. TTTS, sIUGR and twin anemia-polycythemia sequence) require an individualized delivery plan for each pregnancy and fetus (recommendation level C).
The choice of gestational week of delivery for twin chorionic twin pregnancies is debated, with a recommended range of 38 to 39 weeks + 6. The evidence-based medical rationale is mainly derived from fetal or neonatal complications, with less information focusing on maternal complications. Studies have shown that the risk of intrauterine fetal death increases after 38 weeks of gestation, with an RR of 2.116 (95% CI: 1.693 to 2.648) for the risk of intrauterine fetal death by 39 weeks of gestation. The RCOG 2008 clinical guideline suggests that delivery of a single chorionic villous double amniotic sac twin should be planned at 36 to 37 weeks of gestation unless there are other indications for early termination; the American College of Obstetricians and Gynecologists 2014 clinical guideline recommends delivery at 34 to 37 weeks of gestation +6. A 2012 multicenter study of 1,001 twin pregnancies (200 of which were singleton) was conducted. A 2012 multicenter study retrospectively analyzed 1,001 twin pregnancies (200 monochorionic and 801 bimniotic twin pregnancies) and found that perinatal mortality was 3% in monochorionic bimniotic twins compared with 0.38% in bimniotic bimniotic twins; the incidence of intrauterine fetal death after 34 weeks of gestation was 1.5% in monochorionic bimniotic twins but not in bimniotic bimniotic twins.
The rate of perinatal disease was 41% in monochorionic bipamniotic twins delivered before 34 weeks of gestation and 5% in those delivered between 34 and 37 weeks of gestation (P < 0.01), supporting the view that monochorionic bipamniotic twins without comorbidities can maintain pregnancy until 37 weeks of gestation (level of evidence IIa).
Complex twins (e.g. TTTS, sIUGR and twin anemia-polycythemia sequence signs) also have a higher rate of fetal loss in late gestation, a higher rate of medically induced preterm delivery and a poorer perinatal prognosis. There is a lack of clinical studies with large samples, and individualized delivery plans need to be developed for each pregnancy and its fetus. Twin pregnancies are eligible for vaginal delivery, and cervical ripening and induction of labor can be performed if the patient makes a well-informed choice. The specific methods of cervical maturation and induction of labor are similar to those for singleton pregnancies (Level of Evidence III).
Question 16: Does the fetal orientation of a twin fetus affect the choice of delivery method?
(Expert opinion or recommendation) Vaginal delivery may be considered in cases of dichorionic twin pregnancies where the first fetus is cephalic (recommendation level B) based on well-informed consent.
During a twin delivery, about 20% of the second fetuses have a change in fetal position. Therefore, if a vaginal trial of labor is planned, the obstetrician needs to be prepared to assist vaginally and perform a cesarean section on the second fetus, regardless of fetal orientation (Level of Evidence Ia).
Vaginal delivery should be considered in pregnancies with a double chorionic twin and a first fetus that is cephalic first [32]. If the first fetus is cephalic previa and the second fetus is non-cephalic, the first fetus is at greater risk of requiring vaginal assistance or cesarean delivery for the second fetus after vaginal delivery. If the first fetus is breech-first, it is prone to cord prolapse when rupture of the membranes occurs, whereas if the second fetus is cephalic-first, there is a risk of cephalic strangulation of both fetuses, which may relax the indication for cesarean delivery.
A multicenter retrospective study with a large sample of cases published in 2014 showed that after vaginal delivery of twin fetuses with a non-cephalic second fetus, the rate of second fetus cesarean delivery was 6.2%, which was significantly higher than 0.9% for the second fetus in cephalic position, and the proportion of neonates with a 5-min Apgar score <7 was mildly higher (16.0% and 11.4%, respectively, OR=1.42), but neonates in the 2 groups The differences in mortality, stillbirth rate, and NICU admission were not statistically significant. Therefore, the fetal orientation of the second fetus is not the main basis for the choice of delivery method when vaginal delivery is planned for twin pregnancies (level of evidence IIa).
Question 17: What are the issues to be considered in vaginal delivery of twin pregnancies?
Expert opinion or recommendation] Vaginal delivery of twin pregnancies should be performed in a level II or III hospital with an experienced obstetrician and midwife to observe the labor process. A neonatologist should be present during delivery to handle the newborn. An electronic monitor that can monitor both fetuses at the same time should be available to closely monitor the fetal heart rate during labor. In addition, bedside ultrasound equipment should be available in the delivery room to further evaluate the fetal birth pattern and previa of each fetus after delivery. Preparation for emergency cesarean delivery and management of severe postpartum hemorrhage is needed during labor (Level of Evidence III).
Question 18: What is the management of delayed delivery in twin pregnancies?
Expert opinion or recommendation] The risk of severe maternal and fetal infection during delayed delivery of twin pregnancies requires detailed information to patients and their families about the advantages and disadvantages of the risk and careful decision making (level of recommendation C).