TwinsJohn R. MartinelliNBIMC Ob/GynOctober 28, 2013

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.

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

Zygotes – Chorions - Amnions

• Zygosity = Type of Conception

• Chorionicity = # of Placenta’s

• Amnionicity = # of Amniotic Sacs

Monozygotic

• Also known as identical twins.

• No genetic predisposition.

• Fertilization of single ovum.

• Same sex.

• Identical – including HLA genes.

Monozygotic

Dizygotic

Zygotes – Chorions - Amnions• 2/3:

Dizygotic -> Dichorionic, Diamniotic

• 1/3:

Monozygotic -> Monochorionic, Diamniotic (75%)

-> Dichorionic, Diamniotic (25%)

-> Monochorionic, Monoamniotic (1%)

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

Timing of Split

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.

Prenatal Screening

• Biochemical screening for aneuploidy not recommended.

• Quad Screen?

• MSAFP

• NT

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.

Assessment

• Zygosity

DNA Fingerprinting Amniocentesis

Chorionic Villus Sampling

Cordocentesis

• Chorionicity/Amnionicity

Ultrasound @ 10 – 14 weeks

Placenta(s) and Amniotic Sac(s)

Lamba Sign

T Sign

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.

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.

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.

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.

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.

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.

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.

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.

Mortality & Morbidity• Vascular anastomosis of twins

• Single intrauterine demise

• Discordant twins

• Cord entanglement

• Conjoined twins

Vascular Anastomosis

• Only monochorionic twins.

• Approximately 100% of monochorionic twin placentas have vascular anastomoses.

• Variations in the number, size, and direction.

Vascular Anastomosis

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.

TTTS: Stuck-Twin

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.

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.

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.

TRAPS

Vascular Anastamosis Tx• Amniotic septostomy

• Laser ablation

• Selective fetocide

• Serial amnioreduction

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

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.

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.

Cord Entaglement

Conjoined Twins• 1: 55,000 pregnancies

• Monoamniotic.

• Prenatal diagnosis in first trimester.

• Types:

Anterior (thoracopagus)Posterior (pygopagus)Cephalic (craniopagus)Caudal (ischiopagus)

Conjoined Twins

Presentation

• 40% Vertex/Vertex

• 35% Vertex/Non-vertex

• 25% Non-vertex twin A

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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