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OBGYN: Multiple Gestations
Multiple Gestations: OBGYN
73
Anatomy
Graduate
09/10/2011

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Term
Twin pregnancies are divided according to ___ or ___ as these have important implications for pregnancy and infant outcome.
Definition
- zygosity
- chorionicity
Term
Zygosity refers to whether twins arose from one __ __, called ___, or from two __ __, called ___.
Definition
- one fertilized egg, monozygous
- two fertilized eggs, dizygous
Term
Chorionicity refers to ____.
Definition
placentation
Term
Chorion is the ___ of the ___ ___ of land vertebrates, contributing to the formation of the ____ in placental mammals.
Definition
- outermost of the extraembryonic membranes
- formation of the placenta
Term
Amnionicity refers to ___ __ that __ or __ __ __ the __ __ of twins.
Definition
- membrane layers that do or do not separate the gestational sacs of twins
Term
___ ____ twins have NO separating membrane.
Definition
- Monochorionic Monoamniotic (MC/MA)
Term
__ ___ twins have a separating membrane consisting of 2 layers of amnion only.
Definition
Monochorionic Diamniotic (MC/DA)
Term
___ ____ twins have a separating membrane consisting of both chorion and amnion. They may or may not have __ or __ placenta.
Definition
Dichorionic Diamniotic (DC/DA)
separate or fused placenta
Term
Dizygotic twins occur when __ __ __ were fertilized by __ __.
Definition
- 2 separate ova
- 2 sperm
Term
2/3 of the twins in the United States are ___.
Definition
dizygotic
Term
Monozygotic twins occurs when there is division of a __ __ fertilized by a __ __. This accounts for 1/3 of the twins in the United States.
Definition
- single ova
- single sperm
Term
With dizyogtic twinning aka __ __ there are two distinct pregnancies. There is a separate __, __, and __.
Definition
- Fraternal twinning
- chorion, amnion, and placenta
Term
two or more ovum fertilized in a single menstrual cycle:
Definition
dizygotic twinning
Term
Factors that influence dizygotic twinning:
Definition
- race
- hereditary/family history
- maternal age
- parity
- fertility drugs
- geography
- maternal weight and height (heavier more likely to have twins)
- diet
Term
What maternal ages have the greatest incidence of twins:
Definition
- both extremes of the reproductive ages (14-15) and (48-50)
Term
What races are most and least likely to have dyzogtic twins?
Definition
- Nigeria has the highest rate of natural twinning
- Japan has the lowest rate of natural twinning
Term
Monozygotic twinning aka __ __ twinning aka __ __. Cleavage of the fertilized egg happens at various stages during embryogenesis.
Definition
- single ovum twinning
- embryo splitting
Term
The rate for monozygous twinning is __ at __ in __ births.
Definition
- constant at 1 in 250 births
Term
Monozygotic twinning is INdependent of __, __, __, and __. __ and __ __ double the risk of embryonic splitting.
Definition
- independent of race, heredity, age, and parity
- Fertility drugs and ART DO double the risk
Term
If embyronic splitting occurs from __ to __ hours, the monozygotic twins will be Diamniotic, Dichorionic. This occurs 30% of the time.
Definition
- 0-72 hours
- Diamniotic, Dichorionic
- 30% of the time
Term
If embryonic splitting occurs in __ to __ days, the monozygotic twins will be Monochorionic Diamniotic. This occurs 68% of the time.
Definition
- 4 to 8 days
- Monochorionic, Diamniotic
- 68% of time
Term
If embryonic splitting occurs from __ to __ days the monozygotic twins will be Monochorionic Monoamniotic. This happens 2% of the time.
Definition
- 8 to 13 days
- Monochorionic, Monoamniotic
- 2% of the time
Term
If embryonic splitting after greater than 13 days, the monozygotic twins will be ___.
Definition
- conjoined
Term
0-72hrs Diamniotic, Dichorionic 30%
4-8days Monochorionc, Diamniotic 68%
8-13days Monochorionc, Monoamniotic 2%
>13 days Conjoined Twins
Definition
Term
Early assessment of ___ by ___ is essential in the management of multiple pregnancies as the distinguishing features are more difficult to ascertain later on.
Definition
- chorionicity by ultrasound
Term
Female external genitalia on the left and male external genitalia on the right, confirming dichorionic twin gestation with certainty
Definition
Term
The most important step after determining there is multiple gestation, is determining ___.
Definition
zygosity
Term
Reasons to determine zygosity:
Definition
- assess obstretical risks
- guide management
Term
Ways to determine zygosity:
Definition
- ultrasound
- examine placenta
Term
Twin peak aka __ __ is a __ projection of __ tissue emanating from ___ __ placentas and extending between layers of the intertwin membrane. This is characteristic of a __ __ pregnancy.
Definition
- lambda sign
- triangular projection
- chorionic tissue
- fused dichorionic placentas
- Dichorionic,Diamniotic pregnancy
Term
Baby A is the baby that is:
Definition
closer to the exit
Term
Diagnosis of Multiple Gestations when U/S unavailable:
Definition
- family or personal history of twins
- excessive weight gain
- enlarged fundal height
- fertility drugs
Term
Definitive way to diagnose multiple gestations:
Definition
- ultrasound (best in the 1st trimester)
Term
Maternal Complications of multiple gestations:
Definition
- Anemia- 2.5 fold increase
- Hydramnios
- Hypertension, Preeclampsia- 2.5 fold
- Premature labor
- Cesarean delivery
- Abruption- 3 fold
- Urinary tract infections- 1.5 fold
- Postpartum hemorrhage
- Postpartum atony
Term
Discrepancy b/w plasma rise and hematocrit just in normal pregnancy. This discrepancy doubles with twins.
Definition
Term
Hydramnios: many chambers so uterus is expanding more, uterus with twins at 25 weeks is same size a singleton full term uterus
Definition
Term
Maternal Adaption to twins:
Definition
- increase serum level of hormones (progesterone, estrodiol, estriol, hPL, hCG, a-FP)
- Heart rate and stroke volume increase> leading to increased cardiac output
- Systolic and Diastolic Pressure mirror the changes seen in singleton pregnancy
but an even greater drop in the 2nd tri-mester with twins
At the time of delivery the mean pressure is higher in multiple pregnancies
- Plasma volume increases by 50-100%
Leading to increased dilutional anemia
- Uterine volume increases rapidly
- Increase in the Tidal Volume and Oxygen consumption
- Increase in GFR
- Caloric intake increases from 2400 kCal to 3000 kCal/day
Term
Fetal complications of multiple gestations:
Definition
- Malpresentation
- Placenta Previa
- Abruption
- Premature Rupture of Membranes
- Prematurity
- Umbilical cord prolapse
- Intrauterine growth retardation
Term
Unique fetal complications of multiple gestations:
Definition
- monoamniotic monochorionic twins, only happens 1% of the time, mortality rate is 50%
- conjoined twins
- acardiac twins
- twin-twin transfusion syndrome
- discordant twins
- intrauterine demise of one fetus (vanishing twin)
Term
Of liveborn twins, 70-75% are dichorionic diamniotic, and 25-30% are monochorionic diamniotic. Only 1% are monoamniotic.
Definition
Term
With Monochorionic Diamniotic placentas there is lots of vessel communication between the two sides.
Definition
Term
-
Definition
Term
Conjoined twins occur when there is cleavage after day __ when the embryonic __ is formed. Separation is incomplete.
Definition
- 13
- disc
Term
Conjoined twins are categorized by the anatomic location of incomplete splitting:
Definition
- Thoracopagus (anterior)- most common
- Pyopagus (posterior)
- Craniopagus (cephallic)
- Ischiopagus (caudal)
Term
Siamese twins are __ twins.
Definition
craniopagus twins
Term
Acardiac twins occurs in __ twins when there is a placental __ __ anastomosis. This leads to inadequate pefusion of one twin resulting in lethal anomolies. The pump twin is __, the recipient acardiac twin has ___. You treat this by __ __ __.
Definition
- monozygotic
- arterial arterial anastomosis
- pump twin is normal
- recipient acardiac twin has anomalies
- interrupting vascular communication
Term
The acardiac fetus has an unusually long umbilical cord. It had been seen to move sonographically; it had a spinal cord but no brain.
Definition
Term
Normally there should be an __ __ connection between twins, but with Twin Twin Transfusion Syndrome there is an __ __ connection. This means one twins circulation perfuses the other twin. This occurs in 10% of monozygotic twins.
Definition
- arterial arterial
- arterial venous
Term
Outcome of donor twin with Twin Twin Perfusion Syndrome:
Definition
- hypovolemia
- hypotension
- anemia
- oligohydramnios
- growth restriction
Term
Outcome of recipient twin with Twin Twin Transfusion Syndrome:
Definition
- hypervolemia
- hydramnios
- hyperviscosity
- thrombosis
- hypertension
- cardiomegaly
- polycythemia
- edema
- CHF
Term
Twin Twin Transfusion Syndrome treatment:
Definition
- therapeutic amniocentesis, laser

VERY POOR OUTCOMES
Term
If there is a vascular connection across a monochorionic twin placenta, then a twin-twin transfusion syndrome can develop. In this condition, there is diminished blood flow to one twin (the "donor") and increased blood flow to the other twin (the "recipient"). The pale appearing donor is smaller and may die for lack of sufficient blood flow. More commonly, the larger plethoric recipient may die from congestive heart failure.
Definition
Term
__ __ is the most accurate way to assess fetal growth.
Definition
Serial ultrasonography
Term
__ to __% difference in fetal weight suggests clinically significant growth discordance.
Definition
20-25%
Term
Weight discordance of __% or more is associated with a __ fold increase of stillbirth.
Definition
25%
6.5 fold
Term
Intrauterine demise of one fetus (vanishing twin) occurs in __% of twin pregnancies. There is usually __ __ injury to the surviving twin. "Monochorionic twin" as ealry as 12 weeks gestation. List complications of surviving twin:
Definition
- 21%
- profound neurological injury
- cerebral palsy, cortical necrosis, small bowel atresia, multicystic encephalomalacia

USUALLY SIGNIFICANT HYPOTENSION AT THE TIME OF DEATH OF THE CO-TWIN.
Term
Antepartum management goals of multiple gestations:
Definition
- prolong gestation
- increase birth weight
- decrease perinatal morbidity and mortality
Term
Antepartum management during 1st and 2nd trimester of multiple gestations:
Definition
- cervical assessment
- nutritional counseling
Term
3rd trimester antepartum management:
Definition
- cervical assessment
- monitor for signs of preeclampsia
- antenatal testing (biophysical profile)
- monitor fetal growth
Term
Do NOT treat for preterm labor after __ weeks.
Definition
34
Term
Intrapartum management for preterm labor includes ___ ___ and ___.
Definition
- Antenatal steroids
- Tocolytics: Magnesium sulfate, Terbutaline, Procardia, Toradol
Term
calcium channel blocker to stop uterine contractions in preterm labor:
Definition
Procardia
Term
Most common presentation for twin delivery:
Definition
- vertex-vertex> delivery vaginally if possible with double set up
Term
Any presentation other than vertex-vertex twins, a __ should strongly be considered.
Definition
C section
Term
A 36 year old female presents for her initial prenatal appointment. She was treated with Clomiphene citrate for infertility. Her initial ultrasound reveals a twin gestation. This type of twinning is usually:
Definition
Diamniotic, Dichorionic b/c fertility drugs make you release more than one egg
Term
A 20 year old female presents for her prenatal appointment at 21 weeks gestation. She has a known twin gestation. Fundal height has increased 10 cm from the last visit 2 weeks ago. Ultrasound reveals excessive amniotic fluid around the first twin and the second twin has only a small pocket of fluid. This complication of twins is:
Definition
Twin-Twin Transfusion syndrome
Term
The incidence of monozygotic twins is :
Definition
1:250
Term
Which two factors are associated with the highest rate of twinning?
Definition
- Infertility agents
- Maternal age
Term
At the onset of labor the most common presentation for twin gestation is
Definition
cephalic cephalic
Term
If division of the zygote occurs on the fifth day after conception the fetuses will have:
Definition
two amnions, one chorion
Term
The most common type of conjoined twin is:
Definition
thoracopagus
Term
A 24 year old G1P0 has just delivered twins, both male, at 37 weeks. On your initial assessment, you notice the “A” twin is large and plethoricand the “B” twin is small and pale. A CBC is the next most appropriate step because:
Definition
"A" twin is at risk for polycythemia
Term
Discordance in twins is best measured by:
Definition
- Biparietal diameter
- Abdominal circumference
- Femur length
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