Deliveries of multifetal gestations can prove challenging for even the most experienced obstetrics provider.¹ Fetal lie, monitoring challenges with more than one fetus, and the potential need for a cesarean section to deliver one or both fetuses can complicate what would otherwise be a normal delivery. However, a woman laboring with twins may present to the emergency department without sufficient time for transfer to a facility better equipped to manage the intricacies of the labor and delivery process; thus, the emergency medicine practitioner must be prepared to navigate this unique circumstance.

Twin pregnancies are becoming more common in the United States, with an increase of nearly 50% over the last decade.² Several factors including older maternal age, which naturally increases the chance of twinning, and the use of assisted reproductive technologies have led to a higher incidence of multifetal gestations, with twins being the most common type of multiple gestation.^3,4,5 Twin pregnancies are associated with increased maternofetal morbidity and mortality during pregnancy, delivery, and postpartum. Women with twin pregnancies have a higher likelihood of developing pregnancy-related complications such as gestational diabetes and hypertensive disorders of pregnancy.³ In the postpartum period, complications such as uterine atony, postpartum hemorrhage, and postpartum depression are more common in mothers of multiples.³ In terms of fetal risks, when compared to singleton gestations of the same birth weight, twin pregnancies have a higher risk of perinatal and neonatal mortality.¹ In addition, twins tend to deliver at earlier gestations ages, for a variety of reasons, resulting in the morbidity and mortality associated with preterm status.^2,3

The optimal time to diagnose twins is during the first trimester of pregnancy, when the number of placentas and the presence or absence of a membrane dividing the amniotic sacs is more easily identified.³ As the pregnancy continues, the clarity of these markers may diminish. Knowing the D.chorionicity of twins during labor is not vital to a successful delivery, although it may assist with ensuring the correct number of placentas has delivered. The presence of a dividing membrane is reassuring that there are two separate gestational sacs, thus excluding the diagnosis of monochorionic twins (Figure 23.1).

The most appropriate route of delivery for twins has been somewhat controversial over the years.⁷ Although the position of the presenting twin normally dictates whether a vaginal delivery is an option, at times the orientation of the second twin also factors into the mode of delivery.⁸ This partially explains why cesarean section is extremely common in twin pregnancies, accounting for up to 68% of twin deliveries.^7,9 However, a randomized controlled trial compared fetal and neonatal death as well as serious neonatal morbidity among planned vaginal delivery and planned cesarean section in 32 0/7 weeks to 38 6/7 weeks pregnant women with the first twin in cephalic presentation.⁴ Their results show no difference in neonatal morbidity or mortality between the two groups and, in fact, showed improved outcomes in the group delivered vaginally. This study suggests that cesarean section does not offer any advantage in terms of the studied outcomes. If the leading twin is vertex, the recommendation is to proceed with vaginal delivery, and if breech, a cesarean section is planned.^1,4 The risk with delivery of the presenting twin as a breech is head entrapment or extension of the neck, making delivery more difficult and potentially leading to a fetal cervical spine injury. Historically, the teaching was a concern for “interlocking chins” (Figure 23.3). This is actually a very rare event.