**8. Associated risks: vaginal and cesarean delivery**

**5.5. Maternal conditions**

216 Multiple Pregnancy - New Challenges

**6. Exceptional situations**

communication safely [43].

expectant management [51].

vaginal delivery.

**7. Twin-to-twin delivery time intervals**

Higher rates of maternal morbidities are found in multiple gestations, compared to singletons. There is a higher risk of pre-eclampsia, diabetes and post-partum complications, as uterine atony and postpartum hemorrhage. Regardless, maternal conditions are rarely an indication of a cesarean section. An elective cesarean delivery can be performed after maternal request, after exposing the risks of the procedure, as longer maternal hospital stay, increased risk of the newborn going to the ICU due to respiratory problems and increased risks for subsequent pregnancies, as placenta previa and uterine rupture [37]. In those cases, the surgery should be

planned to the appropriate gestational age, considering chorionicity and amnionicity.

Although the data about triplet pregnancies are still limited, and the monoamniotic and diamniotic triplets should be delivered between 32 + 0 and 32 + 6 weeks [38], most studies and guidelines suggest delivery time at no later than 36 weeks, even in uncomplicated triamniotic triplets [6, 39, 40]. The preferred delivery route is the cesarean section because vaginal delivery is associated with an increased risk of adverse outcomes if compared with the cesarean [41, 42]. In conjoined twins, the data available is based in small case report studies and expert opinion, but what is suggested is the delivery time and mode of the viable ones must be near term cesarean section after confirming lung maturity. In selected cases an EXIT procedure can be performed in order to stabilize the fetuses with cardiac union to examine and close the vessel

Another controversial subject about delivery in twins is the time interval between fetuses in

New guidelines such as the American College of Obstetricians and Gynecologists do not recommend an upper limit to the time interval between fetuses, if the fetal heart rate is reassuring, as some studies also suggests [44–47]. However, there are studies that provide evidence of an association, but not necessarily causality, between longer twin-to-twin time interval and poor second twin outcome, such as lower apgar grades and decreasing pH in umbilical arterial blood gas [48–50]. This lack of strong evidence leaves space for different approach and

A very specific approach can be performed in the case of a dichorionic twin pregnancy with spontaneous preterm delivery <24 weeks and never above 28 weeks, which is called delayed interval delivery when the second twin do not have an indication for labor such as infection among other complications. Several techniques and interventions are described but the evidence is not strong, but the main goal is to provide a better outcome for the second twin, and success rates of these particular cases are good according to a systematic review of 2016 [52].

During the last few years, a lot of studies were performed trying to elucidate the question about the best delivery route for twins, according to the associated risks and benefits of planned cesarean section or planned attempt vaginal delivery.

The twin birth study, showed that planned cesarean section was not superior to planned vaginal delivery regarding maternal risk or neonatal mortality or morbidity [53], and ever since some society guidelines suggest attempt to vaginal delivery to diamniotic twin pregnancies if the first twin is in cephalic presentation [54].

The concern about the risks includes the possibility of combined delivery, which involves an unplanned cesarean after attempt of vaginal delivery and is associated with higher second twin morbidity [14] and may be an increased risk of neonatal and/or maternal infection probably because the exposure to labor and rupture of membranes are higher than in a planned cesarean delivery.

Cesarean delivery can expose mothers to short-term risks such as endometritis, wound complications, surgical injuries, hemorrhage [55], although maternal outcomes past 3 month and long-term risks, including abnormal placentation, are similar both ways cesarean an vaginal planned delivery [56, 57].

Newborns delivered by planned cesarean present a higher risk in developing allergic disorders [58–60].
