John R. Martinelli
October 28, 2013
• 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.
Twin 1 : 89
Triplets 1 : 892
Quadruplets 1 : 893
Quintuplets 1 : 894
• Frequency: Highest – Black
Lowest – Asian
• Increased with maternal age and parity.
Zygotes – Chorions - Amnions
• Zygosity = Type of Conception
• Chorionicity = # of Placenta’s
• Amnionicity = # of Amniotic Sacs
• Also known as identical twins.
• No genetic predisposition.
• Fertilization of single ovum.
• Same sex.
• Identical – including HLA genes.
Timing of Split
9 – 12 days
4 – 8 days
0 – 3 days
After amnion and
chorion are formed
After chorion formed
Before amnion and
3, 9, 12, Split after 13 days Conjoined Twins
• 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
• Randomized controlled trials and a meta-analysis of hospital bedrest
in twin pregnancies have shown no reduction in preterm birth or
• 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.
• Most randomized controlled trials have failed to show any benefit of
prophylactic oral or intravenous tocolytic therapy in multiple
• There is moderate evidence against prophylactic tocolysis in the
management of multiple gestation, but it may be indicated on other
• Prophylactic cervical cerclage has not been shown to be effective in
preventing preterm birth in twin pregnancy in observational or
• 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.
• 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
• 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.
• Only monochorionic twins.
• Approximately 100% of monochorionic twin placentas have vascular
• Variations in the number, size, and direction.
Twin-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.
• 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
• 60-100% fetal or neonatal mortality rate.
• Associated with premature delivery.
• Death of one twin is associated with neurologic sequelae in 25% of
Twin Reverse Arterial Perfusion Syndrome
1% of monochorionic
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.
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 death
24% 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
• Risk increased if weight discordance exceeds 25%.
• Discordance is an indicator for an increased risk of IUGR, morbidity,
and mortality for the smaller twin.
• 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.
First twin non-cephalic
IUGR of dichorionic twin
Cord prolapse of 1st twin
Non progress of labor
Collision of both twins
2nd twin transverse after delivery of 1st twin