Chapter 31 : Multiple Gestations

Monochorionic monoamniotic

1 placent & 1 amniotic sac

What are the 3 categories of monozygotic twins:

1. Monochorionic diamniotic 2. Dichorionic diamniotic 3. Monochoirionic monoamniotic

Dichorionic Diamniotic

2 placentas & 2 amniotic sacs

Dizygotic twins arise form:

2 separate zygotes

What is the median gestational age of delivery for twins is?

35 weeks

When compared with singleton pregnancies, twins have a ___ times higher risk of fetal mortality and ___ times higher neonatal morbidity.

4 6

Division of the inner cell mass between ___ to ____ days will result in Monochorionic diamniotic twins.

4 to 8

Omphalopagus

Conjoined twins attached at abdomen

What form of monozygotic twins results when one zygote splits prior to day 4?

Dichorionic Diamniotic

What are the most common form of monozygotic twins?

Monochorionic diamniotic

What is referred to as a zygote?

a fertilized egg

Monozygotic twins arise from:

a single zygote

What is a twin peak sign, lambda sign or delta sign?

a triangular extension of the placenta at the base of the dividing membrane

What does the donor twin often suffer from?

anemia & growth restriction

Why are Dizygotic twins are referred to as fraternal twins?

becuase they have their own genetic structure and can differ from each other in many ways

What additional risk does monochoirionic monoamniotic twins carry?

conjoined twins

Twins who have their own individual amniotic sac are referred to as:

diamniotic

Dizygotic twins are referred to as:

fraternal twins

Amnionicity refers to?

how many amnions or amniotic sacs are present

Conjoined twins can result from?

monochorionic monoamniotic twinning

The presence of 1 yolk sac & 2 fetuses is indicative of?

of a monoamniotic gestation

The presence of 2 yolk sacs & 2 fetuses is indicative of?

of diamniotic gestation

Abnormal anastamoses of placental vessels may result in?

parasitic twin or acardiac twin

The pump twin has a perinatal mortality of 50% to 55%, secondary to what?

polyhydramnios & prematurity

Mothers expecting multiple gestations have an increased risk of developing?

preeclampsia & anemia

Infants born with low birth weight, specifically before 32 weeks gestation, often suffer from:

pulmonary hypoplasia with episodes of hypoxia

What occurs in TTTS?

shunting occurs from one twin to the other,

Conjoined twins have 40% chance for being?

stillborn- many dying within the first 24 hours

What structure develops before the amnion?

the chorion

Most triplet & quadruplet pregnancies result from:

the use of ovulation induction or in vitro fertilization

What are treatment options for TTTS?

therapeutic amniocentesis & endoscopic-guided laser photocoagulation of the communicating placental vessels

Monozygotic twins are always identical twins because:

they share their design from only one fertilized egg

During the first trimester dichorionic twins will have a _______ membrane separating the 2 amniotic sacs.

thick

During the first trimester monochorionic twins will have a _______ membrane or no membrane at all between them.

thin

What are the most common forms of conjoined twins?

thoracopagus(chest) omphalopagus(abdomen)

Triplets can have different combinations such as:

trichoirionic triamniotic and dichorionic triamniotic

When is multifetal reduction used?

when assisted reproduction is used, & resulting in a high of # of multifetal pregnancies

What are the most common form of twinning?

dizygotic

The twin that shunts the blood to the other is called ?

donor twin & is often smaller than the twin receiving the extra blood, the "recipient twin"

If the fetus dies in the 1st trimester & is maintained throughout the pregnancy, it is referred to as:

fetus papyraceus

Patients with multiple gestations may present with the clinical indication of large for dates and also an elevated ______ blood level compared to a singleton pregnancy.

hCG

Dichorionic

having 2 placentas

monoamiotic

having one amniotic sac

monochorionic

having one chorion

Monochorionic diamniotic

having one placenta and two amniotic sacs

Where can the conjoined twins be attached?

head, thorax, abdomen & the lower part of the body

Patients with history of ovulation induction drugs or ART are more likely to not only have multiple gestations but also ______________ pregnancies

heterotrophic

What does the recipient twin often experience?

hydrops & congestive heart failure

If the twins are different sexes then one can assume that the twins are _________.

dichorionic

Twins who have 2 separate placentas are referred to as:

dichorionic

Dizygotic twins always results in ___________ _________ twins.

dichorionic diamniotic -2 amnions & 2 placentas

When twins have TTTS, the resulting sonogram will reveal what?

discordant growth

Multiple gestations beyond twins have an increased likelihood of:

discordant growth, miscarriage, & perinatal death

Sonofindings of Acardiac Twin

1. Normal pump twin 2. Acardiac twin-absent upper body, absent heart, & hydrops

The risk of preterm delivery is increased 7 to ___ times more compared to a singleton pregnancy with an associated low birth weight.

10

Dizygotic

2 ova are fertilized by 2 sperms

What condition is considered to be a severe form of TTTS?

Acardiac twinning

Sonofindings of Twin-Twin Transfusion Syndrome:

1. Monochorionic twinning 2. Discordant fetal growth 3. Oligohydramnios 4. Polyhydramnios around recipient twin 5. Recipient may be hydropic

Diamniotic

Multiple pregnancy with 2 amniotic sacs

Acardiac Twinning is also referred to as?

Twin-reversed arterial perfusion (TRAP) sequence or cardiac parabiotic twinning

What is discordant growth?

a 15% to 25% reduction in the estimated fetal weight of the smaller fetus compared to the larger

With acardiac twinning there is one normal fetus, the "pump twin" & an?

an abnormally developed fetus containing no heart

Monozygotic twins are always:

identical twins

Monozygotic

identical twins that are derived from one zygote

Hypoxia at the the time of birth can cause tiny, fragile blood vessels within the immature brain to rupture, leading to:

intracranial hemorrhage and possible irreversible neurologic complications or death.

Pyopagus

joined at the sacral region or back to back

Twins who share the same amniotic sac are referred to as:

monoamniotic

What form of monozygotic twins results when one zygote splits late beyond the 8th day?

monochoirionic monoamniotic (least common of all)

Same-sex fetuses that have a single placenta and a thin membrane separating them are almost certainly __________.

monochorionic

Twins who have 1 shared placenta are referred to as:

monochorionic

Twins can either be:

monozygotic or dizygotic

Chorionicity is often referred to as:

placentation- how many placentas are present

Stuck twin refers to:

severe oligohydramnios surrounding a twin that appears to be closely associated with the uterine wall

In multiple gestations, the term zygosity refers to:

the # of eggs that are fertilized

The normal fetus maintains the growth of the parasitic twin although the growth is considerably irregular, typically resulting in:

the absence of the head, cervical spine, & upper limbs in the acardiac twin.

What structure forms the placenta?

the chorion

In vanishing twin syndrome, with dichorionic twins the surviving fetus is rarely affected by:

the death of the other fetus

What can produce multiple gestations?

the fertilization of a single ovum the eventually divides or the fertilization go several ova.

What determines how many placentas and amnions there are?

the time at which the division or cleavage of the egg takes place

When vascular products travel from the demised twin to the surviving twin by the means of the common vascular channels within the shared placenta is a complication known as:

twin embolization syndrome

The death of a monochorionic twin during the 2nd & 3rd trimester can lead to life-threatening problems to the surviving twin such as:

twin embolization syndrome affects the central nervous system & kidneys hydrocephalus & porencephaly

What is indicative of a dichorionic diamniotic pregnancy?

twin peak sign

A complication that carries a high mortality rate for monochorionic twins is:

twin-twin transfusion syndrome

Ischiopagus

twins joined at pelvis

Craniopagus

twins joined at the head

Thoracopagus

twins joined at thorax (chest)

The death of a twin, and subsequent reabsorption of the embryo during the first trimester is termed:

vanishing twin

What is performed with multifetal reduction?

with ultrasound guidance, a needle punctures the fetal heart and potassium chloride is injected

With monochorionic twins in the 1st trimester, before 7wks it is helpful to identify the # of ______ _____.

yolk sacs