CHAPTER 31 - MULTIPLE GESTATIONS

Parasitic twin or Acardiac twin.

Abnormal anastomoses of placental vessels maybe result in a;

Twin Reversed Arterial Perfusion (TRAP)

Acardiac twinning may also be referred to as;

Abnormal links between the placental vessels

Acardiac twinning resulting from;

discordant growth

Asymmetry in fetal weight between twins is;

Conjoined twins

Can result from monochorionic monoamniotic twinning. Twins can be attached at the head (craniopagus) thorax (thoracopagus), the abdomen (omphalopagus) the lower part of the body. (ischiopagus -pelvis or pyopagus-sacral region back to back). Most common forms are thoracopagus or omphalopagus.

The most common form of twinning, arise from two separate fertilized ova. Dizygotic twins are referred to as fraternal twins because they have their own genetic structure and can differ from each other in many ways. Dizygotic twinning always results in dichorionic diamniotic twins. That means if there are two placentas, there must be two amnions.

Dizygotic Twinning

Dizygotic twinning

Fraternal twins result from;

Zygote

A fertilized egg is referred to as;

Twin-twin transfusion syndrome

High mortality rate for monochorionic twins. The twin that shunts blood to the other is called the ''donor'' twin and is often smaller than the twin receiving extra blood, the ''recipient'' twin. The donor twin often suffers from anemia and growth restriction, whereas the recipient experiences hydrops and congestive heart failure.

Monozygotic twinning

Identical twins result from;

fetus papyraceus

If the fetus dies in the first trimester and is maintained throughout the pregnancy, it is referred to as;

Pulmonary hypoplasia with episodes of hypoxia.

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

Monozygotic twins arise from a single zygote that splits. They are always identical twins. There are three categories of monozygotic twins. 1-monochorionic diamniotic, 2-dichorionic diamniotic, 3-monochorionic monoamniotic.

Monozygotic Twinning

Preeclampsia and anemia

Mothers expecting multiple gestations have an increased risk of developing;

Chorionicity

Often referred to as placentation, relates to how many placentas are present.

heterotopic pregnancy

Ovulation induction drugs not only increase the likelihood of multiple gestations, but also increase the likelihood of;

Amnionicity

Refers to the how many amnios or amniotic sacs are present;

Monochorionic twinning. discordant fetal growth Oligohydramnios around donor twin. Polyhydramnios around recipient twin. Recipient may be hydropic.

Sonographic findings of Twin-twin syndrome;

Vanishing Twin

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

twin embolization syndrome

The demise of a twin can lead to the development of neurologic complications in the living twin as a result of;

Twin embolization syndrome.

The demise of a twin during the second or third trimester can lead to;

Amnion

The fluid filled sac containing the embryo

Monochorionic diamniotic

The most common form of monozygotic twins is;

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If separate placentas are noted, then the pregnancy must be dichorionic diamniotic. Noting a triangular extension of the placenta at the base of the dividing membrane is indicative of a dichorionic diamniotic pregnancy. This is referred to as the twin peak sign, lambda sign or delta sign.

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The presence of one yolk sac and two fetuses is indicative of a monoamniotic gestation, whereas the presence of two yolksacs is indicative of a diamniotic gestation.

TTTS (twin twin transfusion syndrome)

The shunting of blood from one twin to the other is termed;

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Monozygotic twins arise from a single zygote, whereas dizygotic twins form from two separate zygotes.

A single zygote that splits.

Monozygotic twins result from;

Dichorionic diamniotic twins

The sonographic examination of twins reveals a triangular extension of the placenta at the base of the membrane. This finding is indicative of;

Recipient

The twin that will appear larger in TTTS is the;

Zygosity

Refers to the number of eggs that are fertilized.

During the firs trimester, dichorionic twins will have a thick membrane separating the two amniotic sacs, whereas monochorionic twins will have a thin membrane or no membrane at all between them.

Sonographic Assessment of Chorionicity and Amnionicity;

Acardiac twinning

TRAP syndrome may also be referred to as;

Amnion

The inner membrane surrounding the fetus is referred to as;

Chorion

The outer membrane of the gestation is referred to as the;

Acardiac twinning

There's only one normal fetus, the ''pump twin.'' and an abnormally developed fetus containing no heart. The normal fetus maintains the growth of the parasitic twin, although the growth is considerably irregular, typically resulting in an absence of the head, cervical spine and upper limbs in the acardiac twin. The pump twin has a perinatal mortality of 50-55%, secondary to polyhydramnios and prematurity.

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Twin embolization syndrome can result from the death of a monochorionic twin.

Monochorionic monoamniotic

Twins having one placenta and one amniotic sac are referred to as;

This doesnt occur

Twins having two placentas and one amniotic sac are referred to as;

Dichorionic diamniotic

Twins having two placentas and two amniotic sacs are referred to as;

Monochorionic monoamniotic

Twins that have the threat of being conjoined are;

Dizygotic

Twins that result from the fertilization of two separate ova are called;

Monochorionic

Twins who have one shared placenta are referred to as;

Dichorionic

Twins who have two separate placentas are called;

Discordant fetal growth

Typically the first sonographic manifestation of TTTS is

Twin Embolization Syndrome

Vascular products travel from the demised twin to the surviving twin by means of the common vascular channels within the shared placenta, a complication known as ;

Amnionicity

Wha term relates to the number of amniotic sacs?

Dichorionic diamniotic twins

What can occur as a result of dizygotic twinning?

Monochorionic diamniotic twins. Monochorionic monoamniotic twins. Dichorionic diamniotic twins.

What can occur as a result of monozygotic twinning?

Preeclampsia

What condition is pregnancy induced maternal high blood pressure and excess protein in the urine after 20 weeks gestation?

endoscopic-guided laser photocoagulation

What is a treatment that separates abnormal placental vascular connections between twins that are suffering from TTTS?

Stuck twin

What is it called when a twin fetus, suffering from TTTS, experiences severe oligohydramnios and becomes closely adhered to the uterine wall?

Pyopagus

What is the term for cojoined twins attached at the sacral region?

Pulmonary hypoplasia

What would a newborn most likely suffer from if they were born prior to 32 weeks as a result of multiple gestation complications?

T sign

Which is not a sonographic sign of a dichorionic diamniotic gestation?

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With a monochorionic diamniotic pregnancy, the membrane will be thin and seen separating the junction point with the placenta, a sonographic sign referred to as the ''T sign''

parasitic twin

the abnormal twin in acardiac twinning is also referred to as the;

Discordant growth

described as a 15-25% reduction in the estimated fetal weight of the smaller fetus compared to the larger with twin-twin transfusion syndrome.

Division before day 4. Two separate placentas and two separate amnions.

dichorionic diamniotic twins;

Omphalopagus

Conjoined twins that are attached at the abdomen are referred to as;

Least probable twinning. A late split beyond day 8 postconception. Because of the shared amniotic sac, monochorionic monoamniotic carries the additional risk of conjoined twins.

monochorionic monoamniotic twins;

Most common form of monozygotic twins. Division of the inner cell mass between 4 and 8 days will result monochorionic diamniotic twinning. Both twins share a placenta and are positioned within separate amniotic sacs.

Monochorionic diamniotic twins;

Chorion

The structure that forms the placenta, develops befpre the amnion;

Diamniotic

The term that indicates the presence of two separate amniotic sacs is;

Dichorionic

The term that indicates the presence of two separate placentas is;

Chorionicity

What term relates the number of placentas?

Gestational diabetes

What would not increase the likelihood of multiple gestations?

Monochorionic monoamniotic

Which form of monozygotic twinning is least common?

Stuck twin

when a twin fetus, suffering from twin-twin transfusion syndrome, experiences severe oligohydramnios and is closely adhered to the uterine wall.

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A maternal history of multiple gestations, ART, ovulation induction drugs, advanced maternal age and maternal obesity have all been shown to increase the probability of multiple gestations.