INTRODUCTION — Twin pregnancies are at increased risk of late stillbirth and intrapartum complications, such as fetal heart rate abnormalities and complications related to malpresentation or placentation. This topic will review issues related to the birth of diamniotic twins, such as timing and route of delivery, fetal monitoring, maternal analgesia/anesthesia, and management of delivery. Antepartum assessment of these pregnancies, pregnancy outcome, newborn care and outcome, and issues related to monoamniotic twin pregnancy are discussed separately:
●(See "Twin pregnancy: Overview".)
TIMING OF DELIVERY
Uncomplicated twin pregnancies — The optimum time to deliver uncomplicated twin pregnancies depends on chorionicity and amnionicity. However, scheduling the timing of delivery is not at the discretion of the obstetrical provider in most cases because spontaneous or medically indicated preterm birth complicates over 50 percent of twin pregnancies .
Dichorionic/diamniotic — For uncomplicated dichorionic/diamniotic twin pregnancies, we suggest planned delivery at 38+0 to 38+6 weeks of gestation, in agreement with recommendations from the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) . We believe delivery at this gestational age is optimal, based on review of available data regarding the increased risk of unanticipated stillbirth with expectant management and the low risk of neonatal mortality and morbidity with delivery.
There are no high quality data from randomized trials on which to base a recommendation for the optimal time for delivery of dichorionic/diamniotic twins. Although the authors of a 2016 meta-analysis of cohort studies assessing the prospective risk of stillbirth and neonatal complications in uncomplicated twin pregnancies recommended delivery at 37+0 to 37+6 weeks, we do not believe their data warrant a strong recommendation. In dichorionic/diamniotic twins, they found that the prospective risks for stillbirth and neonatal death were similar for pregnancies between 37+0 and 37+6 weeks (risk difference 1.2 deaths/1000 pregnancies, 95% CI -1.3 to 3.6), whereas the prospective risk for stillbirth exceeded that for neonatal death at 38+0 to 38+6 weeks (risk difference 8.8 deaths/1000 pregnancies, 95% CI 3.6-14.0) . However, neonatal morbidity, including respiratory distress syndrome, septicemia, assisted ventilation, and neonatal intensive care unit admission, was lower at 38+0 to 38+6 weeks than at 37+0 to 37+6 weeks. The findings of the meta-analysis are limited by the absence of data about quality of ultrasound examination, antepartum fetal monitoring, method of delivery, and level of neonatal care. Without this information, it is difficult to assess the impact of a policy of delivering all dichorionic/diamniotic twins at 37+0 to 37+6 weeks of gestation. Therefore, we continue to recommend planned delivery of uncomplicated dichorionic/diamniotic twin pregnancies at 38+0 to 38+6 weeks, although planned delivery at 37+0 to 37+6 weeks is a reasonable alternative based on the limited data included in the meta-analysis.
Monochorionic/diamniotic — We suggest delivery of uncomplicated monochorionic/diamniotic twins at 36+0 weeks of gestation or soon thereafter and by 36+6 weeks. We believe delivery at this gestational age is optimal after review of available data regarding the risks of unanticipated stillbirth with expectant management and the risks of neonatal mortality and morbidity with delivery. This approach is narrower than that in the ACOG and SMFM guideline, which suggests delivery at 34+0 to 37+6 weeks  and the North American Fetal Therapy Network, which suggests delivery at 36+0 to 37+6 weeks . Some authorities have argued for delivery as early as 32 weeks of gestation [5-9].
No randomized trials have evaluated the optimum time for delivery of monochorionic/diamniotic twin gestations. The authors of the 2016 systematic review of the prospective risk of stillbirth and neonatal complications in twin pregnancies discussed above (see 'Dichorionic/diamniotic' above) also assessed timing of delivery in uncomplicated monochorionic/diamniotic twin pregnancies  and recommended delivery at 36+0 to 36+6 weeks in these pregnancies because they observed a trend toward a higher prospective risk for stillbirth than neonatal death beyond this gestational age (risk difference in the 37th week of gestation: 2.5 deaths/1000 pregnancies, 95% CI -12.4 to 17.4). The number of deaths at each gestational age was small, which precluded precise estimates of risk. In addition, as discussed above, the analysis was limited by the absence of data about quality of ultrasound examination, antepartum fetal monitoring, mode of delivery, and level of neonatal care.
Complicated twin pregnancies
Monochorionic/monoamniotic — Monochorionic/monoamniotic twin pregnancies are delivered between 32+0 and 34+0 weeks of gestation because of the high prospective risk for stillbirth compared with neonatal death, despite intensive fetal surveillance. These pregnancies should be under the care of a maternal-fetal medicine specialist when possible, given the complex counseling and delivery planning necessary. Management of monochorionic/monoamniotic twin pregnancy, including the evidence for this approach, is discussed in detail separately. (See "Monoamniotic twin pregnancy (including conjoined twins)".)
Other complicated twin pregnancies — Twin pregnancies can be complicated by a variety of disorders, which may or may not be unique to twin pregnancy. Timing of delivery in these pregnancies is based on the type and severity of the disorder (eg, twin-twin transfusion syndrome, growth restriction, preeclampsia). See individual topic reviews on specific disorders, such as:
DELIVERY SETTING AND ENVIRONMENT FOR PLANNED TWIN DELIVERY — Consideration of the birth setting and capabilities should be assessed in planning for twin delivery. As risks are increased in these deliveries, appropriate personnel should be available at the time of birth. If the option of breech extraction or internal or external version of the second twin is planned, obstetric staff with appropriate training and expertise should be available. Anesthesia should be available in case emergency cesarean becomes necessary. Pediatric staff should be available for assisting the transition of each infant, including resuscitation if needed, and the facility should be able to provide the risk-appropriate level of care for the newborn.
CHOOSING THE ROUTE OF DELIVERY
Overview — Our general approach to choosing the route of delivery in diamniotic twins is described in the following sections and in the algorithm (algorithm 1). Both amnionicity and fetal presentation at the onset of labor affect the choice of delivery route in twin pregnancies. Vaginal birth is preferred for diamniotic twins in which the presenting twin is cephalic at the onset of labor, if appropriate expertise in internal and external version and/or vaginal breech delivery is available and there are no standard indications for cesarean birth . Cesarean birth is preferred for diamniotic twins with a noncephalic-presenting twin, monoamniotic twins, and pregnancies with standard obstetric indications for cesarean birth (eg, placenta previa).
At the onset of labor, approximately 80 percent of first twins are cephalic (42 percent cephalic/cephalic, 38 percent cephalic/noncephalic), and 20 percent are noncephalic (7 percent noncephalic/cephalic, 13 percent noncephalic/noncephalic) . However, the position of the second twin can change intrapartum: in one study, 11 percent of second twins cephalic on admission to the labor unit were noncephalic at delivery, and 30 percent of second twins who were noncephalic on admission were cephalic at delivery .
Diamniotic twins with cephalic-presenting twin — We favor a trial of labor for diamniotic twins with the first twin in cephalic presentation. With appropriate intrapartum monitoring and management, the second twin is not at increased risk of neonatal mortality or morbidity with a planned trial of labor versus planned cesarean birth, even when remote from term and in a noncephalic presentation [12-18]. However, the obstetric provider should be comfortable with potential internal or external version or breech extraction when conducting vaginal birth. In a series including nearly 20,000 twin pregnancies >32 weeks of gestation and the first twin cephalic, 80 percent achieved planned vaginal birth of both twins, 14.6 percent gave birth to both twins by unplanned cesarean, and 5.13 percent gave birth by combined vaginal/cesarean delivery . Approximately 30 percent of the second twins were noncephalic at baseline, and 72 percent of these pregnancies achieved planned vaginal birth compared with 84 percent of twins cephalic-cephalic at baseline.
The Twin Birth Study is the best available evidence that planned cesarean birth does not significantly improve neonatal or early childhood outcome as compared with planned vaginal birth (with cesarean birth if medically indicated) for diamniotic twins where the first twin is in a cephalic presentation. This trial randomly assigned 1398 patients with diamniotic twin pregnancies and the first twin in cephalic presentation (the second twin could be cephalic or noncephalic) to planned cesarean or planned vaginal birth between 37+5 and 38+6 weeks of gestation . The composite outcome (fetal or neonatal death or serious neonatal morbidity) was similar for both groups (planned cesarean: 2.2 percent, planned vaginal: 1.9 percent; odds ratio [OR] 1.16, 95% CI 0.77-1.74). Findings were similar when the analysis was restricted to monochorionic-diamniotic twin outcomes . At two years of age, both groups continued to have similar rates of death or neurodevelopmental delay . Of note, the rate of cesarean birth was 90.7 percent in the planned cesarean group and 43.8 percent in the planned vaginal birth group, illustrating the high frequency of cesarean birth even when vaginal birth is planned.
Approach to cephalic/noncephalic presentation — We offer most patients with cephalic/noncephalic twins a trial of labor with an attempt at breech extraction of the second twin (assuming no contraindications [discussed below]) and plan to proceed to cesarean birth if breech extraction is unsuccessful, given the absence of high-quality data favoring one approach over another. If the patient declines the plan for breech extraction, we give them the option of intrapartum external cephalic version of the second twin or undergoing scheduled cesarean birth of both twins.
However, in the following patients with cephalic/noncephalic twins, we do not offer a trial of labor and instead recommend scheduled cesarean birth of both twins:
●Gestational age <28 weeks
●Estimated fetal weight of the second twin <1500 grams.
In patients with cephalic/noncephalic twins opting for a trial of labor, we would not perform breech extraction in the following settings because of concerns about head entrapment:
●Estimated fetal weight of the second twin 20 percent more than that of the presenting twin (this threshold is not based on specific data). In these cases, we would plan to perform an external cephalic version of the noncephalic second twin after birth of the first twin.
●Prolonged second stage of labor or marked molding of the head of the first twin suggests that the pelvis may not be adequate for a breech delivery. In these cases, we would offer external version or cesarean for birth of the second twin.
When discussing the options of breech extraction or internal and external version with patients, the obstetrician should include information about their experience and comfort level with these procedures. Many obstetricians (43 percent in one study ), based on training and experience, may feel more comfortable performing a cesarean birth. Under these circumstances, cesarean birth of both twins is recommended. This approach is consistent with that of the American College of Obstetricians and Gynecologists (ACOG), which considers vaginal birth a reasonable option in diamniotic twin pregnancies at >32 weeks of gestation with a cephalic-presenting fetus, regardless of the presentation of the second fetus, provided that an obstetrician with experience managing a noncephalic second twin is available .
The safety of this approach is supported by the Twin Birth Study (discussed above) in which planned cesarean birth in the subgroup of cephalic/noncephalic twin pregnancies, which accounted for over one-third of the fetuses, did not reduce the risk of fetal or neonatal death or serious neonatal morbidity compared with planned vaginal birth (with cesarean if medically indicated) . In addition, many observational studies have reported successful vaginal birth of both twins using internal or external version or breech extraction of the second twin [11,23-40]. The second twins of cephalic/noncephalic and cephalic/cephalic pairs generally had similar neonatal outcomes irrespective of mode of birth or procedures performed during the birth. However, successful vaginal birth appeared to be less likely when external version was attempted than when breech extraction was performed immediately after birth of the presenting twin [25,26,33,37]; external version was completed in 40 to 50 percent of cases (the remainder were delivered by cesarean), while breech extraction followed by vaginal birth succeeded in 96 to 100 percent of patients [25,26]. Of note, the mean gestational age was 34 to 37 weeks, and the mean birth weight was 2100 to 2500 grams in these studies.
Diamniotic twins with noncephalic-presenting twin — We suggest cesarean birth when the first twin is in a noncephalic presentation, which occurs in approximately 20 percent of twin gestations. A unique potential complication of vaginal birth of a breech-presenting twin with a cephalic second twin is interlocking chins (ie, locked twins), but this is rare.
There is general consensus in the obstetric community against vaginal birth of the breech-presenting fetus [41,42]. However, some clinicians believe that planned vaginal birth in carefully selected patients by obstetricians experienced in breech vaginal birth is not associated with a higher risk of neonatal mortality and morbidity for either first or second twins than planned cesarean and should be an option that is seriously considered. Randomized trials have not been performed to evaluate the safety of vaginal birth in this setting, but limited data from observational studies are available.
As an example, in a secondary analysis of data from a prospective study (JUMODA) of 298 planned vaginal births of breech-presenting first twins in 176 French hospitals, 185 patients (62 percent) gave birth to both twins vaginally . In all of the pregnancies, the twins were ≥32 weeks and had no major anomalies, birth weights between 1500 and 4000 grams, and a second twin that was not substantially larger than the first twin; cephalic presentation of the second twin was not an exclusion factor. The composite rate of neonatal mortality/severe morbidity for first twins was similar in the planned vaginal and planned cesarean birth groups (1.7 percent [5/298] and 1.9 percent [22/1169], respectively; crude relative risk 0.90, 95% CI 0.34-2.34, which remained statistically nonsignificant in propensity score matching analysis).
Although these data may be reassuring to patients who desire vaginal birth and meet the study's inclusion criteria, there are significant limitations to this study. The cohort of planned vaginal births represented only 20.3 percent of breech-presenting twins. Confidence intervals around the primary outcome are wide, and the study was underpowered to exclude a small increase in neonatal mortality and morbidity associated with planned vaginal birth of a noncephalic first twin. Information on outcomes for cephalic versus noncephalic second twins and occurrence of locked twins was not provided. Importantly, these findings can be generalized only to centers where obstetricians are trained in and accustomed to vaginal birth for breech presentation. While we still recommend cesarean birth for breech-presenting twin pregnancies, we acknowledge that there may be a role for planned vaginal birth under certain limited circumstances.
Trial of labor after previous cesarean birth
●One prior cesarean – We offer a trial of labor to patients with diamniotic twin pregnancies with a cephalic-presenting twin and one prior cesarean birth, provided they go into spontaneous labor. Because the most common initial sign of uterine rupture is fetal heart rate changes, we continuously monitor both fetuses. If this is not technically possible, then cesarean birth is performed.
A meta-analysis of 11 cohort studies including nearly 2500 twin gestations undergoing a trial of labor after a prior cesarean (TOLAC) provided reassuring data . Twins undergoing TOLAC had similar rates of successful vaginal birth and uterine rupture as singletons undergoing TOLAC (vaginal birth: 71 versus 74 percent, OR 0.85, 95% CI 0.61-1.18; uterine rupture: 4/407 [0.98 percent] versus 253/31,630 [0.80 percent], OR 1.34, 95% CI 0.54-3.31). Although twins undergoing TOLAC had higher rates of uterine rupture than twins undergoing a planned repeat cesarean (OR 10.09, 95% CI 4.30-23.69), rates of uterine scar dehiscence, hemorrhage, blood transfusion, and neonatal morbidity and mortality were similar in both groups.
●Two prior cesareans – We suggest repeat cesarean for these patients, but some providers may make this decision on a case-by-case basis, allowing a trial of labor selectively and with very close maternal-fetal monitoring. There are few data to evaluate the safety of TOLAC with twins and ≥2 prior cesarean births.
Very low birth weight twins — We do not consider very preterm gestational age or very low birth weight alone factors in choosing the route of birth. We suggest a trial of labor unless there is a standard indication for cesarean birth (eg, breech presentation, previous classical cesarean).
Although no randomized trials have evaluated the optimum route of birth for these pregnancies, the body of evidence from observational studies suggests that cesarean birth performed because of very preterm gestational age in twins does not improve neonatal morbidity and mortality compared with vaginal birth [45-47]. In cohort studies of twins born at 24+0 to 27+6 weeks (541 twin pairs)  and 26+0 to 31+6 weeks (424 twin pairs) , rates of adverse neonatal outcome and survival to discharge without severe morbidity were similar for planned vaginal versus planned cesarean birth. In a third cohort study, planned cesarean was associated with higher perinatal morbidity and mortality than planned vaginal birth .
Monochorionic/monoamniotic twins — Monochorionic/monoamniotic twins are delivered by cesarean, with rare exceptions, to avoid complications during labor from cord entanglement. The rationale for this approach and other aspects of management of monoamniotic twin pregnancy are reviewed separately. (See "Monoamniotic twin pregnancy (including conjoined twins)".)
MANAGEMENT OF LABOR — Labor management is generally similar to that in singleton gestations (see "Labor and delivery: Management of the normal first stage"). Selected issues are discussed below.
Preparation — Given the increased risk for maternal blood loss in multifetal births, appropriate preparation for possible transfusion should be ensured with adequate intravenous access and blood product availability. Generally, a type and screen should be sent at the time of admission to the labor unit. Our policy regarding oral intake during labor, which is no restrictions until active labor and then restrict to clear liquids, is not different for twin pregnancies.
Ideally, a portable ultrasound machine can be kept readily available to check fetal positions and heart rates and to image the fetus during internal or external version or breech extraction, as needed.
Cervical ripening and oxytocin — Twin pregnancy is not a contraindication to use of cervical ripening agents (eg, prostaglandins, balloon catheter), as they appear to be as safe in these pregnancies as in singleton pregnancies [48,49]. The approach to cervical ripening is the same as in singleton pregnancies. (See "Induction of labor: Techniques for preinduction cervical ripening".)
When indicated, oxytocin for induction or augmentation of labor appears to be effective and safe [48,50]. The oxytocin regimen is the same as in singleton pregnancies. (See "Labor: Overview of normal and abnormal progression" and "Induction of labor with oxytocin".)
Data are conflicting as to whether induction of twin pregnancies is associated with a higher risk for cesarean birth than induction of singleton pregnancies [51-55].
Assessing progress — It is unclear whether labor progress is affected by multiple gestation; studies have reported conflicting results (ie, both faster and slower progression than singleton labor) [56-61]. Differences in cervical dilation and effacement at onset of labor and differences in birth weight may account for the variation among studies.
In the largest series (>2000 twin and >135,000 singleton births), the second stage (defined as time from full cervical dilation to delivery of the first twin) was longer in twins than singletons. For twin pregnancies, the median length in nulliparas was 90 minutes (95th percentile: 233 minutes) and in multiparas 19 minutes (95th percentile: 119 minutes); a second stage longer than the 95th percentile was associated with an increased risk for neonatal intensive care unit admission and need for phototherapy . By comparison, in singleton pregnancies, the median length in nulliparas was 78 minutes (95th percentile: 205 minutes) and in multiparas 10 minutes (95th percentile: 67 minutes).
No information is available on use of an intrauterine pressure catheter in multiple gestations. It can be used to gauge the frequency of contractions if this information is needed clinically and cannot be obtained with an external device, but information about contraction intensity may not be as accurate as in singleton gestations. There is also the possibility of rupturing the second sac; ultrasound imaging during insertion might reduce this risk.
Electronic fetal heart rate monitoring — Multiple gestations are at increased risk of intrapartum complications; therefore, we monitor both twins continuously during labor. Intermittent auscultation is not practical and may not reliably distinguish one twin from the other. Electronic fetal heart rate monitoring is particularly useful for assessing the well-being of the second twin during the high-risk period after birth of the first twin. (See 'Delivery of the second twin' below.)
The fetal heart rate of each twin can be monitored using a single machine with dual-channel capability (waveform 1). The rates are often synchronous, thus requiring frequent careful review of the tracing to make sure each fetus's heart rate is being monitored. It is important to be aware that the maternal heart rate may be recorded and misinterpreted as the second fetal heart rate, and this has been identified as a contributing cause in some antepartum and intrapartum fetal deaths . Some monitoring systems utilize alarms to alert providers that only one fetal heart rate is being recorded by two transducers, and when available these should be utilized. Ultrasound can also be used to assist in ensuring that both fetal heart rates are traced. If two separate monitors are used, their internal clocks must be synchronized, paper speeds must be identical, and contractions must be displayed on both fetal heart rate tracings.
Analgesia and anesthesia — Neuraxial analgesia/anesthesia is generally recommended because it provides good pain relief, does not cause neonatal depression, and is a suitable anesthetic if uterine manipulation (eg, external or internal version, breech extraction) or operative delivery (eg, forceps, vacuum, cesarean) becomes necessary. (See "Neuraxial analgesia for labor and delivery (including instrumented delivery)".)
MANAGEMENT OF DELIVERY OF CEPHALIC/CEPHALIC AND CEPHALIC/NONCEPHALIC TWINS
Delivery of the first twin
Location — When vaginal birth is attempted, the capacity for immediate cesarean birth is important in the event that complications necessitating urgent delivery arise (eg, prolapsed umbilical cord, nonreassuring fetal heart rate, failed breech extraction, or failed internal or external version).
Intrapartum cesarean birth has been reported in 10 to 44 percent of pregnancies in which vaginal births of twins had been planned and may be necessary for delivery of the second twin after vaginal birth of the first twin (see 'Unplanned cesarean birth' below). It is our practice that all patients with twin pregnancies give birth in an operating room where a cesarean can be performed, if needed. In our hospital, patients laboring with twins are transported from a labor room to the operating room upon complete cervical dilation. However, giving birth of cephalic/cephalic twins in a labor room is not unreasonable if the patient can be transported to an operating room rapidly if a cesarean is needed. In these cases, an open operative suite should be immediately available with appropriate personnel for an immediate cesarean birth if indicated.
There are additional advantages to giving birth in an operating room. Because these rooms are typically larger than labor rooms, they better accommodate the extra obstetric, pediatric, and nursing personnel who are present for the birth of two neonates, as well as anesthesia personnel. They also tend to have better lighting than standard labor rooms.
Procedure — Indications for episiotomy and operative vaginal birth, and the procedure for delivery of the cephalic infant, are the same as in singleton births.
●Monochorionic twins – Monochorionic twins are not appropriate candidates for delayed cord clamping because acute and large inter-twin blood transfusion may occur during labor and birth, and the direction of transfusion is not predictable. Signs of acute peripartum twin-twin transfusion syndrome include bradycardia or a sinusoidal fetal heart rate pattern and may necessitate urgent delivery.
Acute anemia has been reported in 2.5 percent of first-born monochorionic twins delivered vaginally , but second-born twins are also at risk if the cord of the first twin is not clamped promptly after its birth. The second twin could develop hypovolemic shock from exsanguinating into the placenta and/or out of the unclamped cord of the first twin . Our practice is to promptly clamp the cords of monochorionic twins.
●Dichorionic twins – For dichorionic twins, we concur with the American College of Obstetricians and Gynecologists (ACOG) recommendation for a delay in umbilical cord clamping for at least 30 to 60 seconds after birth in vigorous term and preterm infants . (See "Labor and delivery: Management of the normal third stage after vaginal birth", section on 'Early versus delayed cord clamping'.)
●Monochorionic/monoamniotic twins – In monochorionic/monoamniotic twin pregnancies, clamping and cutting a tight nuchal cord on the first twin should be avoided since it may be the umbilical cord of the undelivered twin. (See "Monoamniotic twin pregnancy (including conjoined twins)", section on 'Delivery'.)
Labelling — The umbilical cords of twins should be marked with progressive numbers of clamps (eg, one for the first twin, two for the second twin). If surgical clamps are used initially, they should be replaced with the same number of plastic umbilical cord clamps prior to sending the placenta for formal pathologic examination. Recall that "twin A" on ultrasound may not be the first born (especially if a cesarean birth), and this neonate is typically called "baby A" by delivery room and nursery personnel [65-69].
Delivery of the second twin — The general approach to delivery of the second twin after birth of the first twin is shown in the algorithm (algorithm 2).
Assessment — The heart rate and position of the second twin should be evaluated using physical examination, ultrasound, and electronic fetal monitoring. Among cephalic/cephalic twins undergoing a trial of labor, 12 percent of second twins were found to be in a noncephalic presentation after birth of the first twin in one large study . In another one study, 11 percent of second twins cephalic on admission to the labor unit were noncephalic at delivery, and 30 percent of second twins who were noncephalic on admission were cephalic at delivery .
Interval between delivery of first and second twin — Studies undertaken after the universal routine use of electronic fetal monitoring during labor suggest that there does not have to be a specific finite interval between birth of the first and second twin as long as the fetal heart rate tracing is reassuring [71-73]. Electronic fetal monitoring and the availability of real-time ultrasound have enabled obstetricians to identify those second twins who would benefit from expedited delivery, while allowing most cases to be managed expectantly .
Delayed-interval delivery in previable gestations is discussed separately. (See "Multifetal gestation: Role of delayed-interval delivery".)
Cephalic presentation — If the second twin is in a cephalic presentation after birth of the first twin, oxytocin augmentation of labor is sometimes necessary due to a temporary reduction in contraction frequency after the first birth . When the head is engaged, we perform artificial rupture of membranes during a contraction to facilitate delivery. One approach used by some providers when the head is not engaged is to perform a controlled needle puncture of the amniotic sac between contractions to allow slow leaking of amniotic fluid and facilitate descent while preventing prolapse of the umbilical cord.
●Possible role of internal podalic version – If the second twin is cephalic but unengaged after birth of the first twin, some providers perform internal podalic version and breech extraction [39,75]. The rationale is that active management of delivery reduces the chance of complications, such as prolapse of the cord or a hand, or abruption, which would require emergency cesarean birth; however, an improvement in neonatal outcome with internal version versus pushing was not demonstrated by the best available data regarding this issue . In this observational study, which was limited to second twins above 0 station, composite neonatal morbidity for the 487 cephalic twins in the internal version/breech extraction group trended higher compared with the 1769 cephalic twins in the pushing group (3.5 versus 2.1 percent, adjusted RR 1.73, 95% CI 0.98-3.05), but the cesarean birth rate was lower (1.0 versus 3.7 percent). Based on this study, we suggest not performing routine internal podalic version and breech extraction for an unengaged cephalic-presenting second twin, despite a reduced risk of cesarean birth for that twin. Internal podalic version should not be presented to patients as a safer option compared with pushing and should only be performed by experienced clinicians because of the risk for fetal and maternal trauma.
•Procedure – To perform the procedure, the operator places a hand through the dilated cervix to elevate the fetal head higher into the uterine cavity. The other hand or an assistant holds the head in position abdominally. One and then the other foot is grasped; pulling the feet caudally somersaults the fetus to breech presentation, and the breech extraction is completed. The membranes should be left intact until the feet are at the vaginal introitus, though spontaneous rupture during these maneuvers is common.
Noncephalic presentation — If the second twin is not in a cephalic presentation (eg, breech or transverse), our preference is breech extraction if there are no contraindications to this procedure (see 'Approach to cephalic/noncephalic presentation' above).
●Breech extraction – Intrauterine manipulation is aided by ultrasonographic visualization of the orientation between the physician's hands and fetal parts (figure 1A-B)  and can be facilitated by administering nitroglycerin (50 mcg intravenously, may repeat in 60 seconds to a maximum total dose of 250 mcg) or inhalational anesthesia, both of which relax uterine muscle . Effective maternal analgesia is also crucial. Extraction is performed as soon as feasible to reduce the risk that the cervix will contract, potentially entrapping the head.
The fetal feet are grasped, and firm downward traction is used. If both feet cannot be grasped, traction on one foot is usually effective until there is sufficient room to grasp the second foot. Similar to internal podalic version, the membranes are left intact until the feet are at the vaginal introitus, though rupture during these maneuvers is common.
Management of the complicated breech extraction (eg, nuchal arms, head entrapment) is similar to that in singleton pregnancies and described separately. (See "Delivery of the singleton fetus in breech presentation", section on 'Arms' and "Delivery of the singleton fetus in breech presentation", section on 'Head'.)
●External cephalic version – If external version to cephalic presentation is preferred to breech extraction, the procedure is performed in standard fashion. Membranes should be left intact during attempted external cephalic version. Data confirming the safety of an attempt at version with ruptured membranes are not available, though with fetal monitoring and the capability to perform breech extraction or cesarean birth immediately, we consider it an option.
When the fetus is in the desired cephalic presentation for delivery, oxytocin is administered if labor has not resumed. Amniotomy is not performed until after the head is engaged [14,79]. (See "External cephalic version", section on 'Procedure'.)
Unplanned cesarean birth — An unplanned cesarean for delivery of the second twin is not uncommon, occurring in approximately 4 to 10 percent of planned vaginal births [19,80-83]. It is associated with an increased risk of fetal/neonatal death or serious neonatal morbidity compared with vaginal birth of both twins (13.6 versus 2.3 percent in a subanalysis of the Twin Birth Study ). Reasons for unplanned cesarean include maternal complications, malpresentation, cord prolapse, failure to progress, and abnormal fetal heart rate pattern.
●A population-based cohort study of over 61,000 twin births in the United States reported 9.5 percent of second twins overall were born by cesarean after vaginal birth of the first twin . This rate fell to 6.3 percent if the second twin was cephalic  but increased to 24.8 percent if only cephalic/noncephalic live births were considered . In a Dutch study including over 30,000 twin births with a cephalic first twin, 5.13 percent of second twins had an unplanned cesarean birth after planned vaginal birth of the first twin . This rate fell to 2.61 percent if the second twin was cephalic but increased to 10.4 percent if the second twin was noncephalic.
●A cohort study of 130 planned vaginal twin births by a single obstetric practice reported that no patient who had a vaginal birth of the first twin required a cesarean for delivery of the second twin . The authors attributed their success to active management of the second stage of labor by obstetricians experienced in breech delivery and internal podalic version and to their criteria for selecting candidates for vaginal birth. In this group's practice, all twin pregnancies that were undelivered at 38 weeks of gestation underwent induction if they met strict criteria (estimated weight of the second twin ≥1500 grams and no more than 20 percent greater than the weight of the presenting twin, absence of usual contraindications to vaginal birth). Immediately after the vaginal birth of the first twin, the second twin was delivered as a cephalic presentation if the head was engaged, by breech extraction if in breech presentation, and by breech extraction after internal podalic version if in cephalic presentation but unengaged.
MANAGEMENT OF CESAREAN BIRTH — Sometimes extraction of a floating twin is challenging at cesarean. A variety of techniques are effective and are described separately. (See "Cesarean birth: Management of the deeply impacted head and the floating head".)
MANAGEMENT OF THE THIRD STAGE — Twin pregnancies are at increased risk for atony because of increased uterine distention compared with singletons. Our protocol for managing the third stage does not differ in twins compared with singletons, though our threshold to intervene with a second uterotonic medication in these patients is lower, as they are at higher risk for postpartum hemorrhage. (See "Management of the third stage of labor: Prophylactic pharmacotherapy to minimize hemorrhage".)
EXAMINATION OF THE PLACENTA — Examination of the placenta may help to determine zygosity in same-sex twins (algorithm 3) and the pathogenesis of neonatal findings (eg, discordant growth, structural anomalies, or infection).
Vascular anastomoses — In monochorionic twins, vascular anastomoses may be evaluated by placental injection, but this is not routinely performed. The study takes approximately one hour to perform and involves catheterizing the arteries and vein of each umbilical cord and injecting the vessels with a substance, such as dyed undiluted barium sulfate, until the peripheral branches are filled and backpressure prevents further injection . The amniotic membranes are then removed from the chorionic surface, and the placenta is rinsed with cold tap water to improve visualization of the number and type of anastomoses. Several arteriovenous and venoarterial anastomoses in combination with an arterioarterial and/or venovenous anastomosis are seen in 90 percent of placentas. The remaining 10 percent are equally divided between those with only arteriovenous anastomoses and those with no anastomoses [87,88]. (See "Twin-twin transfusion syndrome: Screening, prevalence, pathophysiology, and diagnosis", section on 'Pathophysiology'.)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Multiple gestation".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Having twins (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Timing of delivery – The optimum time to deliver uncomplicated twin pregnancies depends on chorionicity and amnionicity. However, spontaneous or medically indicated preterm birth complicates over 50 percent of twin pregnancies; thus, scheduling the timing of delivery is not at the discretion of the obstetrician in most cases. (See 'Timing of delivery' above.)
•Monochorionic/monoamniotic twins – Monochorionic/monoamniotic twins are delivered earlier. (See "Monoamniotic twin pregnancy (including conjoined twins)".)
•Cephalic/cephalic diamniotic twins – For cephalic/cephalic diamniotic twins, we suggest vaginal delivery in the absence of standard indications for cesarean delivery (Grade 2B). (See 'Diamniotic twins with cephalic-presenting twin' above.)
•Cephalic/noncephalic diamniotic twins – For cephalic/noncephalic diamniotic twins, we suggest a trial of labor and breech extraction of the second twin only if the obstetrician has the requisite experience and if the patient provides informed consent (Grade 2C). (See 'Approach to cephalic/noncephalic presentation' above.)
•Noncephalic presenting twin – When the first twin is not in cephalic presentation, we suggest cesarean delivery (Grade 2C). (See 'Diamniotic twins with noncephalic-presenting twin' above.)
●TOLAC – While we offer a trial of labor after a previous cesarean (TOLAC) to patients with twins and one prior cesarean delivery, there are few data to evaluate the safety of TOLAC with twins and ≥2 prior cesarean deliveries. We advise repeat cesarean delivery for these patients, but some providers may make this decision on a case-by-case basis, allowing a trial of labor selectively and with very close maternal-fetal monitoring. (See 'Trial of labor after previous cesarean birth' above.)
●Fetal heart rate monitoring – The fetal heart rate of each twin can be monitored using a single machine with dual-channel capability (waveform 1). If two separate monitors are used, their internal clocks must be synchronized, paper speeds must be identical, and contractions must be displayed on both fetal heart rate tracings. (See 'Electronic fetal heart rate monitoring' above.)
●Analgesia/anesthesia – Neuraxial analgesia/anesthesia provides good pain relief, does not cause neonatal depression, and is an appropriate anesthetic if uterine manipulation (eg, external or internal version, breech extraction) or operative delivery (eg, forceps, cesarean) becomes necessary. (See 'Analgesia and anesthesia' above.)
●Delivery room – We deliver all twin pregnancies in an operating room where cesarean birth can be performed, if needed. (See 'Location' above and 'Delivery setting and environment for planned twin delivery' above.)
●Cord clamping – Monochorionic twins are not appropriate candidates for delayed cord clamping because acute and large inter-twin blood transfusion may occur during labor and delivery. (See 'Cord clamping' above.)
●Management of the second twin birth – After birth of the first twin, the heart rate and position of the second twin should be evaluated using ultrasound and electronic fetal monitoring. As long as the fetal heart rate tracing is reassuring, there is no duration of elapsed time from birth of the first twin that necessitates intervention to deliver the second twin. Six to 25 percent of second twins will be delivered by cesarean after vaginal birth of the first twin. (See 'Assessment' above and 'Interval between delivery of first and second twin' above.)
•Second twin cephalic – If the second twin is in a cephalic presentation, oxytocin augmentation of labor is sometimes necessary due to a temporary reduction in contraction frequency after the first birth. If the second twin is cephalic but unengaged, some providers perform a controlled needle puncture of the amniotic sac between contractions, and others perform internal podalic version and breech extraction. (See 'Cephalic presentation' above.)
•Second twin noncephalic – If the second twin is not in a cephalic presentation (eg, breech or transverse), our preference is breech extraction if there are no contraindications to this procedure. (See 'Noncephalic presentation' above.)