Multiple Gestations

Patients with multiple gestations will present clinically with

Large for dates and elevated hCG levels compared to a singleton

Twins have a _ times higher risk of _____ _______ and a times higher neonatal ______ ____

4 fetal mortality, 6 morbidity rate

What increases the probability of multiple gestations?

Maternal history of multiple gestations, assisted reproductive therapy (ART), ovulation induction drugs, advanced maternal age, and maternal obesity

Patients with a history of ART or ovulation induction drugs should be evaluated systematically, because they are more likely to have not only multiple gestations but also

Heterotopic pregnancy (IUP & ectopic)

A fertilized egg is referred to as

Zygote

Zygosity refers to

Number of eggs that are fertilized

Monozygotic twins arise from

A single zygote

Dizygotic twins arise from

Two separate zygotes

Chorionicity is referred to as

Placentation

Amnionicity refers to

How many amnions or amniotic sacs present

Dizygotic twins (most common form of twins), arise from

Two separate fertilized ova (fraternal twins)

Dizygotic twinning always results in

Dichorionic Diamniotic twins, however, in early gestation placentas may fuse and appear as one large placenta

Monozygotic twins arise from a single zygote that splits, therefore, monozygotic twins are always

Identical twins

If one zygote splits before day 4,

Dichorionic Diamniotic

If one zygote splits between 4 and 8 days,

Monochorionic Diamnotic

If one zygote splits late

Monochorionic Monoamniotic

What is the most common form of monozygotic twins?

Monochorionic Diamniotic (between 4-8 days)

The least probable form of monozygotic twinning is

Monochorionic Monoamniotic

When two fetuses share the same placenta unfortunately,

Complications are most likely to occur

Because of the late division, monochorionic and monoamniotic twins have an increased risk of

Conjoined twins

In first trimester, two yolk sacs and two amnion sacs is indicative of

Diamniotic gestations

In first trimester, one yolk sacs and two fetuses is indicative of

Monoamniotic gestation

During first trimester, Dichorionic twins will have a

Thick membrane separating the two amniotic sacs

During the first trimester, monochorionic twins will have a

Thin membrane or no membrane at all separating them

If separate placentas are noted, then pregnancy must be

Dichorionic Diamniotic

In addition, noting a triangular extension of placenta at base is indicative of

(AKA twin-peak sign, lambda sign, or delta sign) Dichorionic diamniotic pregnancy

With a monochorionic diamnotic pregnancy, the membrane will be thin and the junction point with placenta will represent a

“T” sign

A compilation that carries high mortality rate for monochorionic twins is

Twin-to-twin transfusion (TTS)

What happens with TTS?

Fetal shunting from one twin to the other. There is a donor and receiver twin. Donor will appear smaller than recipient twin and often suffers from anemia and growth restriction. The recipient experiences hydrops and congestive heart failure.

Treatment for TTS include

Therapeutic amniocentesis and endoscopic- guided laser photocoagulation of communicating placental vessels

Sonographic findings of Twin-to-twin syndrome (TTS)

Monochorionic twinning

Discordant fetal growth

Oligohydraminos around donor twin

Polyhydraminos around recipient twin

Recipient may be hydropic

Abnormal anastomoses of placental vessels may result in a

parasitic twin or acardiac twin (severe form of TTS)

What happens with acardiac twinning?

AKA Twin- Reversed Arterial Perfusion (TRAP)

There is one normal fetus (pump- twin) and an abnormally developed fetus with no heart, spine, and upper limbs. The acardiac twin is maintained from the pump twin.

In TRAP sequence, the pump twin has a perinatal mortality of

50% to 55%, secondary to polyhydraminos and prematurity

Sonographic findings of Acardiac Twin

Normal pump twin

Acardiac twin- absent upper body, absent heart, and hydrops

Conjoined twins can result from

Monochorionic and monoamniotic twinning. They can be attached at the head, thorax, abdomen, and lower part of body

The most common forms of conjoined twinning are

Thoracopagus and omphalopagus (chest and abdomen)

Prognosis is poor with conjoined twins, they have a

40% chance for being stillborn, with many dying within 24 hours

What is vanishing twin

The death of a twin and subsequent Reabsorption of embryo during the first trimester

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

Fetus papyraceus

With dichorionic twins, the surviving twin s is rarely affected By the death of the other, however the death of a monochorionic twin during first trimester frequently leads to the

Death of the other twin

The death of a monochorionic twin during the 2nd or 3rd trimester can lead to life-threatening problems of the surviving twin. Particularly,

The central nervous system and kidneys are affected with a documented 25% risk of death or neurological damage. Hydrocephalus and porencephaly is noted as well

What is Twin Embolization Syndrome

When vascular products as a result of the breakdown of tissues, travel from demised twin to the surviving twin by means of common vascular channels within shared placenta

Most triplets and quadruplets are the result of

Ovulation induction or In Vitro Fertilization

Unfortunately, multiple gestations beyond twins have an increased likelihood of

Discordant growth, miscarriage, and perinatal death.

When assisted reproduction is used and mom is pregnant with multiple babies,

Multifetal reduction may be used, (needle punctures fetal heart and injects potassium chloride)

Mothers expecting multiple gestations have an increased risk of developing

Preeclampsia, anemia, pre-term delivery (increased 7-10 times compared to singleton)

The median GA of delivery for twins is

35 weeks

For triplets and beyond, the GA of delivery is

Before 35 weeks. Before 32 weeks, babies will often suffer from pulmonary hypoplasia with episodes of hypoxia

Hypoxia at time of birth can cause

Tiny, fragile blood vessels within immature brain to rupture, leading to intracranial hemorrhage and possible irreversible neurological complications or death