Complications with Multiples (Lecture 19)

Which has more impact on the timing and frequency of monitoring twin pregnancies? Amnionicity or chorionicity?

Chorionicity

TRUE or FALSE: When dating a twin pregnancy, the shorter CRL is used.

FALSE: When dating a twin pregnancy, the LONGER CRL is used.

TRUE or FALSE: Dichorionic pregnancies are m/c connected vascularly.

FALSE: Dichorionic pregnancies are m/c NOT connected vascularly (NO anastomoses). However, 50% of DC placentas can appear fused.

What are the 3 types of vascular connections b/w MC twins?

- AA: arterial/arterial

- AV: arterial/venous

- VV: venous/venous

What complications can arise from shared placenta and amnion? (HINT: 4)

- Anastomoses

- Lack of membranes

- Conjoined twins

- Cord entanglement

What is a velamentous CI associated with? (HINT: 2)

Inc risk of:

- growth disturbance (FGR)

- TTTS

What is the risk for congenital malformation for DC, MC, and conjoined twins?

- DC = doubled risk than a singleton preg

- MC = doubled risk than a MC

- Conjoined = 100% will have anomalies

In what body system are abnormalities of twins most common in?

Cardiovascular system

TRUE or FALSE: All MC require a fetal echo.

TRUE: A MC gestation is considered an indication for a fetal echo to get additional screening of the heart. This is b/c the m/c abnormalities are reported in the cardiovascular system

TRUE or FALSE: Twins have a higher incidence of single umbilical artery than singletons.

TRUE

TRUE or FALSE: The growth of twins are compared to the growth of singletons.

TRUE: Regardless of twinning type or fetal sex, twins are compared to singleton growth charts to r/o issues.

What are the m/c reasons for FGR in MC and DC twins?

- MC = unequal placental sharing

- DC = less favourable uterine implantation, velamentous CI

What % weight difference b/w twins is concerning?

15-25% weight difference b/w twins indicates growth discordance

TRUE or FALSE: Growth discordance b/w twins is more concerning in the 3rd trim than the 1st trim.

FALSE: Growth discordance b/w twins is more concerning in the 1ST trim because at the 3rd trim, genetics takes over growth. However, in the 1st trim, the twins should be about the same size.

What is a vanishing twin? When does it usually occur? What are the SF?

- One of the twins regresses while the other progresses

- Occurs in 1st trim

- SF: blighted ovum, smaller gs, irregular margin of sac crescent shaped w/ incomplete trophoblastic ring

TRUE or FALSE: A vanishing twin will have adverse outcomes for the surviving twin.

FALSE: Since this is m/c a 1st trim occurrence, the vascular connections of the placenta are not established yet, meaning it does NOT impact the surviving twin.

What is fetal papyraceous? When does it occur? What are the effects in a DC and MC pregnancy?

- Fetus demises but is too large to be resorbed by the body. Therefore, the fetus (stuck twin) is preserved in a distorted form with the water resorbed

- M/c in 2nd and 3rd trim

- DC/DA preg = surviving twin is usually fine b/c of 2 separate placenta

- MC = issues in surviving twin b/c of vasc connections. Demise causes pressure drop in anastomoses

When there is a co-twin demise, what is there an increased risk of in the survivor? What is the original and modern theory for this?

- In MC twins, a singe demise after the 1st trim inc. the risk for cerebral injury to survivor

- Original theory (Twin Embolization Syndrome): thromboplastic material passes to surviving twin circulation, resulting in ischemia that leads to CNS abnormalities

- Modern theory: demise of of one twin causes drop in resistance in anastomoses, causing blood to be shunted away from survivor to due to low BP of demised twin, leading to anemia, hypotension, and hypoperfusion

What is selective reduction? What is the procedure? Name 2 risks.

Abortion of portion of the pregnancy (reducing # of fetuses in the pregnancy)

Procedure:

- DC = potassium chloride injection to fetal heart/UV

- MC = laser ablation to stop blood flow thru umb. cord

Risks:

- Premature rupture of membranes

- Hemorrhage

- Preterm birth

- Neurologic defects in survivor

- Fetal loss

TRUE or FALSE: TTTS only occurs in MC twins.

TRUE

What is twin-twin transfusion syndrome?

Abnormal shunting within anastomoses (AV shunt), resulting in returning blood from one fetus (donor, small) being shunted directly to other fetus (recipient, large twin)

Donor twin = FGR, hypovolemic, anemic, oligohydramnios, small bladder

Recipient twin = macrosomic, hypervolemic, plethoric (too much body fluid), large bladder, cardiomegaly, hydrops

TRUE or FALSE: In TTTS, the donor twin has a better outcome at birth.

TRUE

In TTTS, why does the donor twin have oligohydramnios?

Since the fetus has less fluid, their water goes to their essential organs instead of their bladder, leading to less urine production, causing oligohydramnios. Additionally, since the fetus has less fluid, the fetus will release ADH to retain as much water as possible

TRUE or FALSE: The donor twin in TTTS may have cardiomegaly.

FALSE: The RECIPIENT twin in TTTS may have cardiomegaly b/c since they have increased fluids to intake, their heart pumps faster, making it larger.

At what stage of TTTS is there a 70-100% risk of perinatal loss?

Stage III+

What are the 5 stages of TTTS?

I - Amniotic fluid level different b/w twins

II - Non-vis bladder in donor

III - Absent/reversed UA diastolic flow

IV - hydrops in either fetus

V - IUFD of one fetus

What vessels are assessed w/ Doppler in TTTS (HINT: 3)? What features are indicative of TTTS?

1. Umbilical artery

- Donor (small) = high resistance, reversed flow

- Recipient (large) = low resistance

2. Middle cerebral artery (MCA)

- Low resistance (less O2 = more blood to brain = less resistance)

3. Ductus venosus

- Absent or reversed A-wave (flows away from heart = abn)

In TTTS, which twin will be hypoxic?

Donor - low blood volume = dec. oxygen

What is Twin anemia- polycythemia sequence (TAPS)? What procedure inc. the risk of developing TAPS?

- Unequal passage of RBCs via placental anastomoses, making the donor anemic and the recipient polycythemic (inc RBC)

- After laster treatment for TTTS (incomplete ablation of AV anastomoses)

What does the Doppler show for TAPS?

Doppler of the MCA shows:

- Anemic fetus = elevated PSV (over 1.5 multiples of median)

- Polycythemic fetus = decreased PSV (less than 1.0 multiples of median)

What are the treatments for TTTS and TAPS? (HINT: 2)

- Fetoscopic laster photocoagulation

- Ablation/coagulation of anastomoses b/w twins

What is twin reversed arterial perfusion/acardiac parabiotic twin?

- One twin has absent/severely malfunctioning heart and there is a large unbalanced AA anastomosis within MC placenta

- Blood is directed from UA of pump twin (normal heart) to UA of other twin (recipient twin).

- Result: Therefore, the UAs of recipient twin have reversed flow w/ blood going into fetal heart instead of placenta. The UAs of recipient deliver deoxy blood mostly to lower body, causing the upper body to be malformed

What are the SF for the recipient twin in TRAP? (HINT: 2)

- Malformed fetus above diaphragm (malformed/absent heart, head, upper extremities)

- Reversed flow of UA and UV

What are the outcomes of the twins in TRAP?

Pump/donor twin

- Heart pumps harder to serve recipient = hydrops

- Polyhydramnios

- 50-70% mortality rate

Recipient twin

- Not viable (death in utero or birth)

How are conjoined twins formed?

Latest splitting of monozygote

What are thoracopagus twins?

Conjoined twins connected at the chest (m/c)

What are the m/c type of conjoined twins?

Thoracopagus

What are xiphopagus twins?

Conjoined twins connected at the xiphoid

What are omphalopagus twins?

Conjoined twins connected from the xiphoid to the umbilicus (may have 6 vessel cord)

What are pygopagus twins?

Conjoined twins connected back-to-back (sacral)

What are craniopagus twins?

Conjoined twins connected head-to-head (fusion of skull)

What are ischiopagus twins?

Conjoined twins connected side-to-side (pelvis)