Twins
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Transcript of Twins
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TwinsJohn R. MartinelliNBIMC Ob/GynOctober 28, 2013
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Stats
• 1% of all pregnancies.
• 97% of multiple pregnancies are twin pregnancies.
• Double the chance to have twins if conception is within one month after stopping OCP.
• Increased with ART (1970’s).
• Increased perinatal mortality & morbidity.
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Stats
Hellin’s Law
• Twin 1 : 89• Triplets 1 : 892
• Quadruplets 1 : 893
• Quintuplets 1 : 894
• Frequency: Highest – Black Lowest – Asian
• Increased with maternal age and parity.
• ART
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Zygotes – Chorions - Amnions
• Zygosity = Type of Conception
• Chorionicity = # of Placenta’s
• Amnionicity = # of Amniotic Sacs
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Monozygotic
• Also known as identical twins.
• No genetic predisposition.
• Fertilization of single ovum.
• Same sex.
• Identical – including HLA genes.
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Monozygotic
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Dizygotic
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Zygotes – Chorions - Amnions• 2/3:
Dizygotic -> Dichorionic, Diamniotic
• 1/3:
Monozygotic -> Monochorionic, Diamniotic (75%)
-> Dichorionic, Diamniotic (25%)
-> Monochorionic, Monoamniotic (1%)
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Timing of SplitMonoamniotic monochorionic
Diamniotic monochorionic
Diamniotic dichorionic
9 – 12 days 4 – 8 days 0 – 3 days
< 1 % 75 % 25 %
After amnion and chorion are formed
After chorion formedBefore amnion formed
Before amnion and chorion formed
3, 9, 12, Split after 13 days Conjoined Twins
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Timing of Split
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Diagnosis of Twins• History
Ovulation inducing drugs?
• Symptoms
Magnified symptoms.Nausea, vomiting, abnormal bleeding, excessive weight gain,
pressure symptoms, dyspnea, dyspepsia.
• SignsAnemia, edema, HTN, abnormal weight gain.Uterus larger than date.Multiple fetal poles.
FHS.Ultrasound.
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Prenatal Screening
• Biochemical screening for aneuploidy not recommended.
• Quad Screen?
• MSAFP
• NT
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Prenatal Screening
Genetic Testing
• Age 32 consider invasive testing.
• Amniocentesis/CVS uncertain risk with twin gestation.
• Age 32 same Down’s Syndrome risk as singleton age 35.
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Assessment
• Zygosity
DNA Fingerprinting Amniocentesis
Chorionic Villus Sampling
Cordocentesis
• Chorionicity/Amnionicity
Ultrasound @ 10 – 14 weeks
Placenta(s) and Amniotic Sac(s)
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Lamba Sign
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T Sign
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Cervical Assessment
• Transvaginal US cervical assessment in the prenatal period has not been determined due to lack of controlled studies.
• Good evidence that premature cervical change by digital examination predicts preterm birth in twins.
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Home Uterine Monitoring
• No reduction in the incidence of preterm labor, advanced cervical dilation at presentation, or preterm birth in well-controlled randomized clinical trials.
• Moderate evidence against home uterine activity monitoring in multiple gestation.
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Pre-Term LaborBedrest?
• Randomized controlled trials and a meta-analysis of hospital bedrest in twin pregnancies have shown no reduction in preterm birth or perinatal death.
• In uncomplicated twin pregnancies, hospital rest may result in increased risk of preterm birth and maternal psychosocial stress.
• In women with twin pregnancy at high risk for preterm birth because of premature cervical change, there is no evidence that hospital bedrest will reduce the rate of preterm birth.
• There is insufficient evidence to support prophylactic activity restriction or work leave in multiple gestation.
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Pre-Term LaborTocolytics?
• Most randomized controlled trials have failed to show any benefit of prophylactic oral or intravenous tocolytic therapy in multiple gestation.
• There is moderate evidence against prophylactic tocolysis in the management of multiple gestation, but it may be indicated on other grounds.
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Pre-Term LaborCervical Cerclage?
• Prophylactic cervical cerclage has not been shown to be effective in preventing preterm birth in twin pregnancy in observational or controlled trials.
• There is moderate evidence against routine prophylactic cervical cerclage in multiple gestation.
• Cerclage may be indicated for the treatment of incompetent cervix or other specific circumstances.
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Pre-Term LaborCervicovaginal Fibronectin
• High NPV
• PPV for delivery before 37 weeks is 60 percent for patients in preterm labor, 45 percent in asymptomatic high-risk women, and 30 percent in asymptomatic low-risk women.
• No interventional trials.
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Mortality & Morbidity• Twins = High-risk pregnancy.
• Fetal mortality rate for twins is 4x the mortality rate for single births.
• Neonatal mortality rate for twins is 5x the mortality rate for single births.
• Increased prevalence of low birth weight infants secondary to prematurity and IUGR.
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Mortality & Morbidity
• Gestational HTN 3x greater risk – with earlier onset and increased severity compared to single birth.
• Anemia 2X greater risk compared to single birth.
• Congenital Birth Defects 2X greater risk of neural tube defects, gastrointestinal, and heart anomalies.
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Mortality & Morbidity• Vascular anastomosis of twins
• Single intrauterine demise
• Discordant twins
• Cord entanglement
• Conjoined twins
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Vascular Anastomosis
• Only monochorionic twins.
• Approximately 100% of monochorionic twin placentas have vascular anastomoses.
• Variations in the number, size, and direction.
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Vascular Anastomosis
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TTTSTwin-Twin Transfusion Syndrome
• TTTS results in hypoperfusion of the donor twin with hyperperfusion of the recipient twin.
• Donor twin becomes hypovolemic and oliguric/anuric.
• Oligohydraminos develops in the amniotic sac of the donor twin.
• Oligohydraminos can result in “Stuck-Twin” phenomenon with the twin fixed against the uterine wall.
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TTTS: Stuck-Twin
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TTTS• Hydrops fetalis in either twin.
• Donor twin secondary to anemia and/or high-output heart failure.
• Recipient twin secondary to hypervolemia.
• Recipient twin risk of hypertension, hypertrophic cardiomegaly, disseminated intravascular coagulation, and hyperbilirubinemia after birth.
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TTTS
• 60-100% fetal or neonatal mortality rate.
• Associated with premature delivery.
• Death of one twin is associated with neurologic sequelae in 25% of surviving twins.
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TRAPSTwin Reverse Arterial Perfusion Syndrome
• 1% of monochorionic.
• Arterio-arterial anastomosis.
• 55% mortality in pump twin secondary to polyhydramnios and/or high-output cardiac failure.
• Acardiac twin receives blood supply via “pump” twin.
• Results in absent/rudimentary development upper body structures.
• Invasive treatment dependent on fetal progress of pump twin.
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TRAPS
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Vascular Anastamosis Tx• Amniotic septostomy
• Laser ablation
• Selective fetocide
• Serial amnioreduction
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Single Fetal Demise
• 2-6% of twins pregnancies.
• Up to 25% in MC twin pregnancy.
• Increased perinatal morbidity and mortality of the surviving co-twin.
Related to blood loss of surviving twin.19% perinatal death24% having serious long-term sequelae
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Discordant Fetal Growth• Secondary to different genetic growth potentials, structural anomaly
of one fetus, or irregular placental implantation.
• Aneuploidy, congenital anomaly, or viral syndrome affecting only one fetus must also be considered when discordant growth is identified.
• Risk increased if weight discordance exceeds 25%.
• Discordance is an indicator for an increased risk of IUGR, morbidity, and mortality for the smaller twin.
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Cord Entanglement• 70% of MCMA twins.
• Major cause for sudden intra-uterine fetal demise.
• Ultrasound diagnostic.
• Close fetal surveillance from 24 weeks onward.
• Prophylactic delivery via caesarean section at 32 to 34 weeks.
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Cord Entaglement
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Conjoined Twins• 1: 55,000 pregnancies
• Monoamniotic.
• Prenatal diagnosis in first trimester.
• Types:
Anterior (thoracopagus)Posterior (pygopagus)Cephalic (craniopagus)Caudal (ischiopagus)
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Conjoined Twins
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Presentation
• 40% Vertex/Vertex
• 35% Vertex/Non-vertex
• 25% Non-vertex twin A
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C-SectionElective/Scheduled
First twin non-cephalicConjoined twinMonoamniotic twinPlacenta previaIUGR of dichorionic twinCongenital abnormality
EmergencyFetal distressCord prolapse of 1st twinNon progress of laborCollision of both twins2nd twin transverse after delivery of 1st twin
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