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Information about Twins

Published on March 11, 2014

Author: secondopinion2



With the use of fertility enhancing medications, advance maternal age pregnancies and just the natural order od twinning, this pregnancy presentation has become more common among providers. Here we explore the etiology, presentation and management of twin pregnancies.

TWIN GESTATION By La Lura White MD Maternal Fetal Medicine

TWIN GESTATION  Multiple gestations have become one of the most common high-risk conditions encountered by the practicing obstetrician/gynecologist.  Since 1980, the number of twins delivered in the United States has risen over 80%, mainly secondary to ART, ovulation induction agents and AMA.  Now twins represent approximately 3% of all live births.

TWIN GESTATION  Despite the fact they account for only a small percentage of all live births, they are responsible for a disproportionate share of perinatal morbidity and mortality:  17% of all preterm births less than 37 weeks, 23% of early preterm births less than 32 weeks, 24% of all low– birth-weight (LBW) (<2,500 g) 26% of all very low– birth-weight (VLBW) (<1,500 g).  Because of the increased prematurity and LBW, twins are at an approximate 7-fold greater risk of dying before their first birthday compared with singletons.

TWIN GESTATION  Epidemiology :Twin birth rate in the United States 33.3 per 1,000 births  Japan: 6.7/1000 (lowest)  Africa: 40/1000 (highest)  Triplets are about 1 in 7,500 births (1/5 major handicap)  Quadruplets are about 1 in 650,00 births (1/2 major handicap)

TWIN GESTATION  Average birth weight 2,347 g  Average gestational age at delivery 35.3 wk

TWIN GESTATION  Multifetal gestations also are associated with significantly higher maternal morbidity and associated health care costs.  6 times more likely to be hospitalized with complications.  Hospital costs for women with multiple gestations are on average 40% higher than for women with gestational-age matched singleton pregnancies.  Neonatal intensive care unit (NICU) admission is required: one fourth of twins three fourths of triplets, virtually all quadruplets average NICU stays  18 days (twins), 30 days (triplets), 58 days(quads)

TWIN GESTATION  Monozygotic: (33%)  Splitting of an embryo after fertilization.  Identical  Dizygotic: (67%)  Fertilization of more than one egg.  Non-identical

TWIN GESTATION  Dizygotic  Incidence varies  Race: 7 to 10/1,000 Caucasian, 10 to 40 /1,000 African descent, 3 /1,000 Asians  Personal hx (2X)  Family hx (maternal side)  Increasing maternal age  Increasing parity  Increasing body mass  Monozygotic  Incidence relatively constant 3-5/100  Largely independent of race, heredity, age and parity  Assisted reproductive therapy

TWIN GESTATION  Affect ART  Incidence of monochorionic twins with ART 1-5% compared with the background rate of 0.4%.  Manipulation zona pellucida may cause a defect that leads to premature and partial hatching of the blastomeres  Slowed movement through the fallopian tube.

TWIN GESTATION  Chorionicity: # placentas Monochorionic (1) Dichorionic(2)  Amnionicity: # amnions Monoamnionitic (1) Diamnionitic(2)

Twin Gestation  Dizygotic  Diamnionitic  Dichorionic  Two complete placental units are produced, each composed of an amnion and a chorion.  The placentas themselves may be separate or fused.  The dividing membrane will always consist of four layers.

TWIN GESTATION  Monozygotic  # placentas depends on the time at which twin division occurs.  If division of the zygote occurs in the first 3 days, two complete placental units will be formed and the dividing membrane will contain two amnion and two chorion layers, just as with DZ.  At about day 3, the syncytiocytotrophoblast cells, which will give rise to the chorion, begin to differentiate from the periphery of the blastocyst.  If embryonic division occurs between days 3 and 8, the placentation will be a single chorion that has now already differentiated and two amnions that have not yet begun to form.

TWIN GESTATION  The dividing membrane will be thin because it consists of only two opposed amniotic membranes without the intervening chorionic layers.

TWIN GESTATION  The amnion differentiate by about day 8.  If embryonic division occurs between days 8 and 13, the twins will share a single amnion and chorion.  No dividing membrane separating the fetuses.  Allows for potentially lethal entanglement of the umbilical cords.

TWIN GESTATION  Monochorionic/Monoamnionitic  40% mortality (cord entanglement)  Serial ultrasonographic assessment of fetal growth (TTTS common).  Daily fetal kick counts beginning at 26 weeks.  Nonstress testing three times per week beginning at 26 weeks.  Antenatal glucocorticoid administration at 32 weeks and amniocentesis for fetal lung maturity.  Elective delivery at 34 to 35 weeks if fetal lung maturity not previously confirmed.  Cesarean delivery usually recommended.

TWIN GESTATION  Embryonic division, which occurs after day 13, also results in monochorionic, monoamniotic placentation.  There is physical attachment of the fetuses producing conjoined twins.  Thoraco-omphalopagus (28%)  Thoracopagus (18.5%)  Omphalopagus (10%)  Craniopagus (6%)

TWIN GESTATION  TABLE 1 Placentation based on age of embryonic splitting Age of embryonic splitting % in monozygotic twinning < 4 days after fertilization Dichorionic diamniotic (33%) 4 to 8 days (stage of inner cell mass) Monochorionic diamniotic (65%) 8 to 12 days (stage of embryonic disc) Monochorionic monoamniotic (1%) >13 days Conjoined twins

TWIN GESTATION  Identification of Zygosity of Twins:  DZ  Different sex  Two separate placentas  4 layers in the dividing membranes (thick)  MZ  Dividing membrane contains only amniotic layers  Monochorionic placenta (70%)  Monochorionic same sex twins

TWIN GESTATION  Either DZ or MZ  If the dividing membrane has 4 layers (two amnion and two chorion layers: diamniotic, dichorionic)  The infants are the same sex.

Twin Gestation  U/S techniques for determining chorionicity and amnionicity  Best U/S for determining chorionicity and amnionicity (first trimester).  Vaginal sonogram is preferred, due to its high resolution.  Early in pregnancy focus on the gestation sacs and yolk sacs.

TWIN GESTATION  Before 10 weeks’ gestation, several sonographic findings can help determine chorionicity and amnionicity. (1) the number of observable gestational sacs. (2) the number of amniotic sacs within the chorionic cavity. (3) the number of yolk sacs.

 Number of Gestational Sacs .  Each gestational sac forms its own placenta and chorion.  Thus, the presence of 2 gestational sacs implies a dichorionic pregnancy.  Single gestational sac a monochorionic placenta. TWIN GESTATION

TWIN GESTATION  Number of Amniotic Sacs Within the Chorionic Cavity  In diamniotic twins, separate and distinct amnions may be visible on ultrasound.  The amnion grows outward from the embryonic disk, and before 10 weeks the separate amnions of a diamniotic pregnancy will not have enlarged sufficiently to contact each other and create the inter-twin septum.  Each single amnion is extremely thin and delicate and endovaginal imaging is often successful in differentiating separate amnions.

Twin Gestation Amnionicity: # yolk sac number  The number of yolk sacs present is equal to the number of amnions.  If two yolk sacs, it's considered a diamniotic gestation,  If only one yolk sac is seen, the gestation is monoamniotic.

Twin Gestation Second Trimester:  Fetal sex visualization  Separate placentas  Thickness membrane layers  "lambda" or "twin peak" sign or T-sign

Twin Gestation  Membrane thickness and chorionicity.  In dichorionic diamniotic pregnancies, the membranes dividing the two amniotic cavities is thick (>2mm)consist of two layers of chorion and two layers of amnion, in contrast.  Monochorionic diamniotic pregnancies,the dividing membranes consist of two layers, the dividing membrane will be thinner in monochorionic twin pregnancies (<2 mm )

Twin Gestation  Lambda or twin peak sign  In 1981, Bessis and Papiernik reported that a projection of placental tissue into the intertwin membrane could be imaged in 20 of 24 dichorionic twin pregnancies and in none of six monochorionic pregnancies  They coined the descriptive term, "lambda" sign, for this finding, which roughly 10 years later again came to prominence as the "twin peak" sign  Best seen in the second trimester

TWIN GESTATION  T-sign:  Monochorionic gestation.  The membrane has a flat interface with the single placenta.


TWIN GESTATION  Vanishing Twin Syndrome  Reabsorption of one twin early in pregnancy.  Asymptomatic.  5% of all patients with first-trimester bleeding may be experiencing a vanishing twin.  Prognosis for the surviving twin is excellent when silent reabsorption occurs in the first trimester.

TWIN GESTATION  Fetal Risk  Placental abruption  Stillbirth/Neonatal death  IUGR  Cord accidents  Congenital anomalies  Umbilical Cord Prolapse  Fetal Malpresentation  TTTS and TRAP (monochorionic)

TWIN GESTATION  Maternal complications:  Anemia  Hyperemesis  Gestational diabetes  PTL/PTD  Pre-eclampsia  Hypertension  Antepartum/post partum hemorrage  Polyhydramnios  UTI

TWIN GESTATION  Acute fatty liver, which is marked by severe coagulopathy hypoglycemia hyperammonemia,  Can lead to fetal or maternal death.  Postpartum period can be complicated by pancreatitis or diabetes insipidus or both.

TWIN GESTATION  Management  Maternal weight gains of 24 lb by 24 weeks and overall weight gains of 40 to 45 lb.  Increase to 3,000 kcal/d.  Iron (60 mg per day) and folic acid. (1 mg per day)  Reduce activity and increase rest.  Consider work restrictions especially after 28 weeks.

TWIN GESTATION  Clinic visits at least every 2 weeks after 24 week.  Fetal Movement Count daily after 32 weeks.  Obstetric Ultrasound every 4-6 weeks after diagnosis Assess for Placenta Previa Assess Fetal Growth, r/o discordance  Bi-weekly-Weekly Nonstress Test after 32 weeks Assess fetal well-being Predict cord compression

TWIN GESTATION  Interpertation of Multiple Marker Screening:  Have a decreased sensitivity for aneuploidy and a higher false-positive rate compared with its use in singletons.  Down syndrome detection rates in both first and second trimester serum screening is about 52% for twins with a 5% screen positive rate.  Suggested to use first-trimester nuchal translucency (NT) measurement between 10 and 14 weeks to evaluate aneuploidy.

TWIN GESTATION  Timing of Delivery  The lowest fetal death rate per 1,000 singleton conceptions was 0.9 at 3,700 to 4,000 g between 40 to 41 weeks.  The lowest fetal death rate for twins was 3.3 per 1,000 conceptions at 2,500 to 2,800 g at 36 to 37 weeks gestation.  The incidence of both stillbirth and early neonatal death gradually declined until 37 to 38 weeks gestation for multiples and increased thereafter.  By 38 weeks gestation, asymmetric growth restriction is present in almost half of twin pregnancies.  Available data do not support the prolongation of a twin gestation past 38 weeks.

TWIN GESTATION  Intrapartum  When vaginal birth is attempted, the delivery room should be doubly set up for possible emergency cesarean, including immediate availability of anesthesia and neonatal services.  Intrapartum ultrasonic scanning capability.  Uterotonics available.  Availability of blood and blood products.

Twin Gestation  Presentation  First twin presents vertex: 75%  Both twins vertex: 45%  One twin vertex, one twin Breech 37%  Both twins Breech 10%

TWIN GESTATION  Twin A vertex, twin B vertex  Twin A vertex, twin B nonvertex  Twin A nonvertex.

TWIN GESTATION  Twin A Vertex/Twin B Vertex (40%)  More than 80% of vertex/vertex-presenting twin gestations are successfully delivered vaginally.  The presentation of the second twin should be reconfirmed following delivery of the first as a change in the presentation may occur in 10% to 20% of cases.  There is no evidence that perinatal outcomes for VLBW (<1500 gm) twins are improved by cesarean delivery.  Vaginal delivery is associated with a lesser degree of respiratory distress and pulmonary disease in the neonatal period.  Nor is there evidence to support the need for a cesarean based on discordance in the size of the twins, even if twin B is substantially larger than twin A.

TWIN GESTATION  Twin A Vertex/Twin B Nonvertex (40%)  Vaginal delivery of the nonvertex second twin by breech extraction appears to be the best approach for infants over 1,500 g.  Most clinicians would not recommend attempted breech extraction if the second twin was anticipated to be significantly larger (>500 g) than the presenting twin.  Recommendations for route of delivery for a nonvertex twin B whose birth weight is estimated to be less than 1,500 g is not so clear, literature mixed.  External cephalic version for the nonvertex second twin after delivery is an option.

TWIN GESTATION  Twin A Nonvertex (20%)  C/S recommended  Possibility of interlocking  Breech twin A is free to extend its head during labor as a result of the space created by twin B with increased risk cervical spine injury.

TWIN GESTATION  OBJECTIVES: To assess neonatal morbidity in twin pregnancy according to the planned mode of delivery.  METHODS: A retrospective cohort study of 758 consecutive sets of twins born after 35 weeks of gestation with a cephalic-presenting first twin was undertaken in a level III maternity unit.  The primary outcome was a composite measure of neonatal mortality and morbidity, including pH less than 7.0, 5-minute Apgar score less than 4, neonatal intensive care unit transfer more than 4 days, pneumothorax, and fracture.  Neonatal Outcomes of Twin Pregnancy According to the Planned Mode of Delivery; Schmitz, Thomas MD,, Carnavalet, Céline de Carné MD,

TWIN GESTATION  RESULTS: Vaginal or cesarean delivery was planned for 657 (86.7%) and 101 (13.3%) women, respectively.  Among planned vaginal deliveries:  515 (78.4%) patients delivered both twins vaginally  139 (21.1%) had a cesarean delivery during labor  3 (0.5%) had cesarean delivery for the second twin.  Neonatal Outcomes of Twin Pregnancy According to the Planned Mode of Delivery; Schmitz, Thomas MD,, Carnavalet, Céline de Carné MD,

TWIN GESTATION  After vaginal birth of the first twin, the mean intertwin delivery interval was 4.9±3.2 minutes.  Excluding pregnancy complications, the neonatal composite morbidity for the second twin did not differ between planned cesarean and planned vaginal delivery (5.0% compared with 4.7%)  Neonatal composite morbidity of first twins did not differ between groups.  CONCLUSION: For twin gestations with a cephalic-presenting first twin, planned vaginal delivery after 35 weeks of gestation in selected women remains a safe option in centers used to active management of the second twin delivery.  Neonatal Outcomes of Twin Pregnancy According to the Planned Mode of Delivery; Schmitz, Thomas MD,, Carnavalet, Céline de Carné MD,

Twin Gestations  Other complications  IUFD of one twin  Twin-Twin Transfusion Syndrome (TTTS)  TRAP (Twin reversed arterial perfusion syndrome)  Delayed interval delivery

TWIN GESTATION  IUFD of One Twin  Single fetal demise occurs in 2% to 5% of twin gestations (3-4X increase with monochorionic gestations).  When death of one fetus occurs in a dichorionic gestation, the risk to the surviving co-twin is minimal, although higher rates of preterm labor or PPROM.  Monochorionic gestations deliver soon as fetal maturity  25% mortality rate  “acute intertwin transfusion syndrome.”  5% to 25% of the surviving monochorionic twins have ischemic end-organ injury (heart,kidneys brain), most frequently neurologic (cortical necrosis).

Twin Gestation  Twin-to-twin transfusion syndrome (TTTS)  Complicates about 15% of monochorionic twin gestations and is responsible for 17% of the perinatal mortality in multifetal gestations.  Results from a shared placenta,in which deep vascular anastomoses develop between their circulations.

TWIN GESTATION  The donor twin or “pump” twin bleeds into the circulation of a recipient twin.  The donor twin become anemic, hypovolemic, hypoxic, oligohydramnios and IUGR.  Ischemic organ damage involving the brain, kidneys, or bowel.  Can fix against the intertwing membrane “stuck twin”

TWIN GESTATION  The recipient twin becomes volume overloaded, polycythaemia, polyuric polyhydramnios and hydrops.

Twin Gestation  Sonographic features  Marked size disparity in sixe fetuses, discordance in size equal or over 20%.  Disparity in size between the two amniotic sacs.  Disparity in size of the umbilical cords.  A single placenta.  Abnormal Doppler S/D ratio  Hydrops or evidence of congestive heart failure

TWIN GESTATION  Prognosis  When the disease manifests during the second trimester there is a high risk of perinatal morbidity and mortality.  Intrauterine hypoxia, preterm delivery and death of the fetus (usually the donor) with subsequent death or hypoxic-ischemic sequelae in the surviving twin (5-10% develop neurological sequale).

TWIN GESTATION  Treatments which have been advocated include digoxin, serial amnioreduction, prostaglandin inhibitors, “give and take” transfusion, selective fetocide, laser ablation, and septostomy.  The length of this list demonstrates how elusive development of optimal therapy has proven.  Milder cases are treated with amnioreduction/septostomy, and more severe with laser or fetocide.

TWIN GESTATION  OBJECTIVE: The objective of the study was to review current controversy on laser therapy (LT) vs serial amnioreduction (SA) performed for twin-twin transfusion syndrome (TTTS).  STUDY DESIGN: A search in PubMed from 1997–2007 was performed.  Inclusion criteria were diamniotic monochorionic pregnancy, TTTS diagnosed with standard parameters well defined.  Diagnostic criterion for TTTS: discordance of amniotic fluid in the 2 sacs: maximal vertical pocket 8 cm or greater in the recipient's cavity and 2 cm or less in the donor's cavity.  Laser therapy and serial amnioreduction as treatment for twin-twin transfusion syndrome: a metaanalysis and review of literature

TWIN GESTATION  RESULTS:  Ten articles provided 611 cases of TTTS (LT: 70%; SA: 30%) and included 4 studies comparing the 2 treatments (395 cases: LT, 58%; SA, 42%).  Fetuses undergoing LT were more likely to survive than fetuses undergoing SA. Laser therapy and serial amnioreduction as treatment for twin-twin transfusion syndrome: a metaanalysis and review of literature  Other studies:  Comparison of treatments suggests that laser leads to more single survivors and amnioreduction more double survivors.  Perinatal survival rates of <20% without treatment have improved to >50% with modern treatments.

TWIN GESTATION TRAP: Twin reversed arterial perfusion syndrome (TRAP)  Prevalence: 0.3:10,000 pregnancies, 1% monozygotic twin pregnancies.  Definition: A complication of monozygotic twin pregnancies in which one fetus develops normally (pump twin) and the second twin (recipient twin) demonstrates cardiac maldevelopment ranging from complete absence of heart tissue to some formation of rudimentary myocardia and gross anomalies including absent head and extremities.  Pump twin develops congestive heart failure ascites, pleural effusions, poly-hydramnios, skin edema.

TWIN GESTATION  Extremely poor prognosos  Various treatment modalities are based on the premise of interrupting vascular connections.  Intrafetal radiofrequency ablation (RFA

TWIN GESTATION  Objective: The objective of the study was to review perinatal outcomes in pregnancies treated with intrafetal radiofrequency ablation (RFA) for twin reversed arterial perfusion (TRAP).  Study Design: Perinatal outcome data from a quaternary care referral center were abstracted from a chart review of pregnancies with TRAP sequence treated in the midtrimester with umbilical cord RFA of the perfused twin.  Intrafetal radiofrequency ablation for twin reversed arterial perfusion (TRAP): a single-center experience. Livingston, Jeffrey C. MD; Lim, Foong-Yen MD; Polzin, William MD; Mason, Jennifer RN; Crombleholme, Timothy M. MD

TWIN GESTATION  Results:  Twenty-one pregnancies with TRAP sequence were evaluated.  Twelve of 13 pump twins treated with RFA (94%) survived to 30 days of life.  The average gestational age at birth was 37 weeks (range 26–39 weeks).  Conclusion: Primary therapy with RFA is a successful modality for pregnancies complicated by TRAP sequence.  Intrafetal radiofrequency ablation for twin reversed arterial perfusion (TRAP): a single-center experience. Livingston, Jeffrey C. MD; Lim, Foong-Yen MD; Polzin, William MD; Mason, Jennifer RN; Crombleholme, Timothy M. MD

TWIN GESTATION  Delayed interval delivery  Diamniotic, dichorionic twin gestation where the loss of the presenting fetus is the consequence of extrusion following either PPROM or true cervical incompetence.  Adjunctive rescue cerclage appears to offer a better chance of greatly prolonging the interval between deliveries.  Aggressive perioperative tocolysis and broad-spectrum antibiotic coverage after delivery of the previable fetus.  Perioperative indomethacin for prophylactic tocolysis.

TWIN GESTATION  Specific pathogens such as gonorrhea, chlamydia, and group B streptococci should be identified and treated.  Following delivery of the first fetus, the umbilical cord is tied, cut short, and allowed to retract back into the uterus.  At that point, most clinicians place a 5-mm Merseline band using the McDonald technique as a rescue cerclage procedure.  Tocolytic therapy, antibiotic coverage, and hospitalized observation are continued for variable periods of time along with intensive maternal and fetal surveillance.

TWIN GESTATION  Conclusion:  Twin pregnancies have higher mortality and morbidity complications compared to singleton gestations.  Require physician due dilligence.  May need co-management with peri-natal consultants.  Affect outcome for mother and both.

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