Multiple+Gestation

toc =Definition=
 * pregnancy with twins and higher order multiples (eg, triplets, quadruplets)

http://www.thepregnancyzone.com/wp-content/uploads/2009/02/multiple-pregnancies.jpg

=Epidemiology=
 * Incidence of monozygotic twin births is constant worldwide, 4 per 1000 live births
 * Incidence of dizygotic twin and higher births varies by race and maternal age
 * In 2005, twin births accounted for 3% of all births and triplet and higher order births accounted for 0.2%
 * Rate of twin births increased by 70 percent between 1980 and 2004, and the rate of higher-order multiples (triplets or more) increased four-fold between 1980 and 1998 secondary to increase in maternal age at conception and increased use of assisted reproduction
 * Since 2004, prevalence of twin deliveries in the U.S. has remained stable (32 per 1000 live births), prevalence of higher order multiple deliveries has been decreasing

=Placentation of Twins= ==== http://www.health.sa.gov.au/ppg/Default.aspx?PageContentMode=1&tabid=75

=Pertinent Physiologic Changes=
 * Cardiac output increases by 60% in twin pregnancies, compared to 45% in singleton pregnancies
 * Plasma volume increases by 65% by term in twin pregnancies, compared to 50% in singleton pregnancies
 * Blood volume increases by 60% in twin pregnancies, compared to <45% in singleton pregnancies
 * Effects of aortocaval compression exaggerated by size & weight of uterine contents
 * Exaggerated pulmonary changes with multiple pregnancies: decreased FRC, increased oxygen consumption

=Fetal Complications=
 * Preterm delivery
 * 60% of twins delivered before 37 weeks, 96% of triplets born before term
 * Twin-to-twin transfusion
 * Most monochorionic twin placentas have vascular anastomose, most inconsequential
 * Deep arteriovenous vascular communications can lead to twin-to-twin transfusion
 * Recipient twin at increase risk for cardiac failure secondary to volume overload
 * Donor twin at increase risk for IUGR and anemia
 * Tx options: decompression amniocentesis, interruption of the placental vessel communications with endoscopic laser coagulation, amniotic septostomy, and selective feticide
 * Malpresentation
 * Cord entanglement
 * Umbilical cord prolapse
 * Intrauterine growth retardation (IUGR)
 * Congenital anomallies
 * Polyhydramnios

=Maternal Complications=
 * Preterm labor
 * Prolonged labor
 * Preterm premature rupture of membranes
 * Pregnancy-induced hypertension
 * Placental abruption
 * DIC
 * Operative delivery
 * Uterine atony
 * Antepartum & postpartum hemorrhage
 * Odds ratio for severe hemorrhage in multiple gestation pregnancy is 2.29 compared to singleton pregnancy

=Anesthetic Management= >>> as needed by the obstetrician
 * Labor & Delivery
 * Epidural anesthesia is recommended for non-emergent cases because of the often rapidly evolving nature of labor & delivery of multiples
 * Given increased risk of aortocaval compression & hypotension it is recommended to place neuraxial anesthesia in lateral decubitus position
 * Internal podalic version and total breech extraction of twin B may be attempted.
 * E ffective and potentially denser neuraxial analgesia may be necessary
 * Uterine relaxation may be required. Recommendations include nitroglycerin sublinguinal 400-800 μg or nitroglycerin IV 50-250 μg
 * Anticipate rapid changes between the birth of twin A and twin B (ie. preparedness for emergency extension of epidural anesthesia, syringe of 3% 2-chloroprocaine
 * Majority of anesthesia-related maternal death related to failed intubation, failed oxygenation & ventilation, and pulmonary aspiration of gastric contents
 * Exaggerated capillary engorgement during multiple gestation pregnancy-->airway edema, increased incidence of difficult airway

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